Boreholes

[RamdomChances]

I've split the last three posts off and made a new"irrigation" thread

[brahmburgers]

I'm one of those guys who had a well drilled - they put in a 4" PVC casing - but the screw ends stuck in to the space - preventing me from lowering my submersible pump. When I called the foreman of the job - he was angry and called me things that I'm glad I didn't understand. I suggested he fashion a plunger made from a motor cylinder head welded to rods that could be extended - thereby cutting off (or bending) the tips of the screws. he told me they're required by law to attach the lengths of pipe with screws. His crew did something else which pissed me off - they dropped a smaller diameter pvc pipe - 4 meter length into the finished well. I found out when I went to plumb the well and measured it at 6 meters less deep than paid for (you can guess about those mysterious 2 meters). He told me they did that to keep me from dropping my pump to the bottom. I told him that I know about sell drilling and that I was royally pissed at him for plugging the bottom 4 meters of my well.

Two key points of this story are:

#1 NEVER PAY BEFORE THE JOB IS DONE AND ALL'S BEEN THOROUGHLY TESTED!!!!!

#2 Stay directly on the job site for every minute the crew is there - even if it's days on end. If you can't be there, appoint someone with cojones to stay on the site - watching every tiny thing that's going on.

Another thing the drilling crew did was toss all types of garbage in the bushes and one time I caught a worker changing some gunky thick oil and was about to pour the skuzz right by the well-head!!!! I reprimanded the little f#cks - and should have kicked them all off the job at that moment.

[BigA]

I did see any mention in this thread about using a sand or gravel pack around the well screen. Is that not done in Thailand?

I did not see anything discussed about gravel packs in an alluvial floodplain. It is this is type of well that could be used to flood out a rice field. It is possible to pump over 1000 GPM with an 8 inch submersible turbine and a 15 HP submersible motor. A jetted well could be used for the same purpose under the same conditions with suction pump if the water table was high enough but it would not be good as a properly constructed gravel pack using either a lineshaft or submersible turbine.

I saw them using an A frame and small diesel engine to power a tight quarters rotary drilling rig in Hua Hin, in the city.

For the guy who mentioned drilling in granite that woould be real expensive and the best way to go would be a big air rotary rig. I ve seen these on the highway there and they do have them. They are something like you might see with a US firm that drills rock wells to a substantial depth of say 900 to 1500 feet. Sometimes those deeper wells in certain areas produce salt water making them pretty useless as now you must factor in reverse osmosis. Salt water intrusion is a big problem in areas near the coast where overpumping has ocurred.

Some folks mentioned about jet pumps. Single pipe jet pumps claim to be good to 30 m but fact of the matter is tht their performance falls off drastically as the upper limit is approached. Two pipe jets can work substantially deeper but are inherently inefficient due to the wasted energy. All water pumps including submersibles will lock up and fail at some point if they are abused and run very long ior too often in an out of water condition. Lightning strikes are particularly hard on submersible pumps and motors. And believe it or not lightning has a tendency to strike in the same place twice.

There is also such a thing as a solar powered pump. They don't pump very much volume but if set up to pump into a holding tank they could work with a an above ground jet or centrifugal pump. In Surin I noticed they were using about 2 inch jetted sand point with an above ground jet that should be real deep.

[robint]

what a fant\astic post from you guys, real nuts and bolts stuff

i empathise with the sabotage factors. they seem to get special pleasure from dicking over the flang. wouldnt dare do it to an influential tao khae.

I dont see any mention here about the mineral content of the borehole water when used for irrigation. in the north east large areas of land have been spoiled by mineral salts building up in the topsoil

Indeed the fashion for getting rid of all the trees is in itself creating some problems as they traditionally kept the aquifer at arms lenght, just a snippet i saw somewhere some time ago.

nothings ever simple.

another point to consider is the cost of running your pump

it should be simple to estimate the cost of running a rig 24/7

ill put my thinking cap on unless someone has some live figures??

Edited December 5, 2006 by robint

[BigA]

I did see any mention in this thread about using a sand or gravel pack around the well screen. Is that not done in Thailand?

I did not see anything discussed about gravel packs in an alluvial floodplain. It is this is type of well that could be used to flood out a rice field. It is possible to pump over 1000 GPM with an 8 inch submersible turbine and a 15 HP submersible motor. A jetted well could be used for the same purpose under the same conditions with suction pump if the water table was high enough but it would not be good as a properly constructed gravel pack using either a lineshaft or submersible turbine.

I saw them using an A frame and small diesel engine to power a tight quarters rotary drilling rig in Hua Hin, in the city.

For the guy who mentioned drilling in granite that would be real expensive and the best way to go would be a big air rotary rig. I ve seen these on the highway there and they do have them. They are something like you might see with a US firm that drills rock wells to a substantial depth of say 900 to 1500 feet. Sometimes those deeper wells in certain areas produce salt water making them pretty useless as now you must factor in reverse osmosis. Salt water intrusion is a big problem in areas near the coast where overpumping has ocurred.

Some folks mentioned about jet pumps. Single pipe jet pumps claim to be good to 30 ft but fact of the matter is that their performance falls off drastically as the upper limit is approached. Two pipe jets can work substantially deeper but are inherently inefficient due to the wasted energy. All water pumps including submersibles will lock up and fail at some point if they are abused and run very long ior too often in an out of water condition. Lightning strikes are particularly hard on submersible pumps and motors. And believe it or not lightning has a tendency to strike in the same place twice.

There is also such a thing as a solar powered pump. They don't pump very much volume but if set up to pump into a holding tank they could work with a an above ground jet or centrifugal pump.

In Surin I noticed they were using about a 2 inch jetted sand point with an above ground jet.

[rods]

BOREHOLES

Lots of us have water boreholes and there are some of us who would like a water borehole.

But you get boreholes and you get boreholes i.e. some will work good & proper for a long time, and some will be nothing but trouble trouble trouble….because the borehole industry in Thailand, like all industries, has its "cowboys".

Some things you can do and some things to look out for when selecting the right man to do the job.

1) Jump in the pickup and drive around a bit – check out who else around you has a borehole and have a chat with them. Find out:

- how deep the hole is

- how much water it produces p/day

- is it year round (or if it changes, by how much does it change).

- what pump do they use (submersible or plunger type – down to around 10m you can get away with a plunger type, much further you're best off with a submersible, they are more expensive)

- how long has it been in use

- lastly, who bored it and what did it cost.

Check out as many as you can around your village/area – that will give you a realistic idea of what you can expect to get from a borehole on your land. You may even want to get a sample of the water and test it yourself for nitrates/nitrites/ calcium ect ect (done easily & cheaply). If its just for the house and garden 3 cubic meters volume a day is fine – which you can pump out with a couple of truck batteries if you have no ac mains power. Yup, so boreholes in rural areas do make a lot of sense.

Generally you have 2 sizes in Thailand: for domestic use you don't need more than a 6" diameter borehole, but for agriculture use and small businesses you want 12" diameter borehole (that's not to say 6" won't do – it can, and often does – just that you'd be better off volume wise if it was 12" diameter).

Check too if you need permission – some areas you'll have to go off and have a chat with the local Phu Yai (village head or District Head at the local district office, and in other areas no-one cares) – but check. The only time you'll get a "no" answer is if you're in an area that is surrounded by industry and the ground water is known to be not safe, or if there is a ground water quota in your area which is been exceeded (there some areas around Bangkok like that, where some industries lift large quantities of H2O from the ground, but out in the "sticks" I have heard of no restricted areas for quota based reasons).

Now's the time to have a chat with the guys who dig the holes – and to take note what you have been told by others, compare it carefully with what the borehole digger tells you – because they can tell some tall stories – for every 10 boreholes dug, at least half of them won't be serviceable after 5 – 10 years and its usually because they weren't dug properly in the first place, not because there isn't any water.

So what are the problems:

1) Slurry Slurry Slurry – other than fuel it's the boreholers biggest expense, but it's the most important component in boring. It will determine how long the borehole lasts and it will determine how many times you have to lift your pump to take stones out the impeller or indeed, replace your pump. The slurry is a mud that is injected down the hole and (because of its density) is used to lift all the loose dirt and in particular the stones, out of the hole as it is sunk. A lot of cowboy borers just do not use it because it cuts their expense. It must be used. It also ensures that the side of the hole are consistant – it will seep into the uneven side wall forming a consistant smooth surface which consolidates the wall and helps to prevent it from collapsing in over time – nothing worse than having a borehole wall that has collapsed in at 30 meters and compressing part of the tube wall – stopping you from retrieving your expensive submersible pump to get the stones out the impeller! So when you go round to see the guy (always best to go & see him first – and then follow it up with a meeting at your place), just look around his yard to see if there are slurry settling tanks lying around. If he uses slurry he'll have settling tanks lying around because they like to collect it as it comes up, let it settle and pump it back down again. No tanks then ask him if you uses slurry. If he says not needed, then move on. IT IS NEEDED to do the job properly – simple as that.

2) Borehole tubing –you get borehole tubing and you get borehole tubing. The cowboys will use the thinnest stuff they can get away with. Go check out the tubing yourself – get a quote from the boreholer, then ask him what the tubing costs, get that taken off and go get it yourself – so you know what's been used and get advise from the hardware store as to what is good tubing and what is not. Don't skimp on the lining.

3) Joining the tubes in the hole: 3 methods – threaded, screwed, pvc adhesive. Use screws and you are asking to be screwed. They will rust if not stainless steel, which will mean if ever you have to lift the lining you will not be able to. If not correctly screwed in they can break, or just as bad – as someone else has reported: they stuck through so far into the hole in his case they prevented him from getting the pump down the hole. The sharps ends can also wreck havock on the power supply cable in the hole over time. PVC adhesive would be a better choice, but again, it's adhesive strength can breakdown over time which again will prevent you from lifting the tubes if you ever need to. End threaded tubes are the best – they form a good tight joint and wont separate.

4) Dropping the pump: if using a submersible use 2 (TWO) stainless steel wire cables – not one. If one snaps you're buggered – try lifting a 10kg submersible from 30 meters on it's power cable. Not wise. Use two cables so you have redundancy and ensure they are stainless steel not normal multi-strand wire steel.

5) Who to use: well, I assuming you have been speaking to the locals who have boreholes and they have all had theirs done by the same guy and they have all been going for 5 or 10 years,, then I guess that's a fair bet. But failing that, and having understood all the above will be adhered to, what else: well, ask the guy if he has hydrology maps for your area. All the professionals will have maps and water table data for your area and will be able to tell you the mean, low and high water table levels for your area, season to season for the last 20 years – something that has been and is monitored very carefully by the authorities all over Thailand.

6) Get a good concreate cap poured around the borehole at ground level – and have a lockable cap on the top of the tube (to stop rubbish getting into the tube and someone nicking your submersible pump – they do get nicked).

How deep will your borehole have to be – well, about as deep as those around you who have boreholes, but there is no average – each area, depending on its elevation above sea level will have its water table at a different height relative to the surface – and will be affected by the geology of the region. Some areas are as shallow as 6 – 10meters for good all year round water supply, and in other areas (like where I am) you have to go down 80 – 100 meters to get year round water. Clay areas shallow, chalky areas deeper, and the deepest boreholes are found in the sandstone and granite areas – which also give the best water as the sandstone acts as a brilliant filter. Chalky areas make the water real hard with calcium.

If anyone has their own "borehole experience" to add – go ahead.

Tim

Edited December 14, 2006 by rods

[rods]

Brilliant post, Tim (and others).

I'm about to get a borehole done on our land in Amphur Makham, Chantaburi. Anyone know of a reliable contractor there, or have other useful local info, please?

Rods

Edited December 14, 2006 by rods

[old wanderer]

Back in the late 70's I bought a 5000 acre ranch. I had a fellow come out to drill some 6" stock wells for me. Well I ended up trading a 5th wheel trailer for his Cable Tool well drilling rig. (He had bought it and hated the work).

With this cable tool rig I was able to drill several 18" 900' well down through quite a bit of lava rock. My best well pumped 3500 gal/min. with a 200 HP electric motor.....

Doing these small holes like you are talking about I would drill with my smallest bit (8") and take a saw and slice cuts just the width of the cirlular saw blade around the bottom 15' or so of the 6"PVC pipe that I would glue. Most of the house hold and stock well I drilled were about 100'. I would then drop about 1 cu/yd of pea gravel around the outside of the casing, drop in a bag of cement to seal off the ground water and fill the rest with dirt. with a cement cap.

I could pull my rig over in the evening and raise the boom, back in the morning and drill the well, set the casing and be home the next night.....easy $1000. I really wish it was no so insanly expensive to bring equiptment too Thailand, as I still have about 10 tones of tools sitting on a friends ranch that I never go around to selling.

My wife and I will be moving to Thailand in a few years and we have 38 rai up in the mountains above Sara Buri. While we do have some irrigations water available, it would be nice to have a good producing well.

[robint]

you could strip the rig down and bring it in as used agricultural parts. thats what all the naughty boys do here. but it sounds like a big piece of kit.

Ive seen our local homemade version. it can go down 100' and set a 4" pvc pipe. the thai guys worked in saudi and got his knowlegde from there. he came home and built his own out of local bits and pieces and put it on the back of a 6 wheel siuzu truck chassis. it works, ive seen it churning away, looks very primitive but he guarantees his work and has a fair reputation but on the khorat plateau, you cannot be sure if you will hit salt laden water, whose mineral content will quickly destroy land. he doesnt gurantee that, only that he will get you water. in average conditions it takes him 3 days

i dont know any more details but theres no rock drilling involved as far as i know, sand and gravel

[macb]

Interesting reading:

We have a bore hole/Well drilled in early 2005 and works well, I have 2000 litre tank mounted on a purpose built tower with store and pump house beneath as in pic cost 7000 bht including ITC pump.

(23 metres)

Got a question for you

I have two pumps ITC pumps 1 pumps from the bore to the tank and 2 pumps under pressure to the house the pressure is good, but the water pulsates with the pump I assume, I have looked at the pressure switch on the pump it looks to be sealed, now I am assuming the water pulsates because that the volume of water in the pump at that time am I correct??

[Naam]

I have two pumps ITC pumps 1 pumps from the bore to the tank and 2 pumps under pressure to the house the pressure is good, but the water pulsates with the pump I assume, I have looked at the pressure switch on the pump it looks to be sealed, now I am assuming the water pulsates because that the volume of water in the pump at that time am I correct??

******

obviously you need a pressure tank to stop too much pump on/off cycling and to avoid burning the relays.

[macb]

I have two pumps ITC pumps 1 pumps from the bore to the tank and 2 pumps under pressure to the house the pressure is good, but the water pulsates with the pump I assume, I have looked at the pressure switch on the pump it looks to be sealed, now I am assuming the water pulsates because that the volume of water in the pump at that time am I correct??

******

obviously you need a pressure tank to stop too much pump on/off cycling and to avoid burning the relays.

Educate me Dr Nam tell me more are we talking about another tank or the one on top what do I need to do to fix it?

[Pond Life]

I dont know what an ITC pump is, but it sounds to me like you dont have a pressure resevoir.

If you dont have a resevoir then as soon as you turn on a tap the pressure drops & the pump runs, if the pump is supplying more water than is coming out of the tap then the pressure will quickly rise until the pump cuts out, but the pressure will soon drop again & the pump will come back on.

The pump in this situation will keep turning on/off quickly which is bad for everything & will give you pressure pulsations at the tap.

What you need is either what I call a well pump (dont know if thats the correct name) it is available almost everywhere includeing carrefour & lotus, its an all in one unit, connect the inlet to your tank & the outlet to you house supply. The pump itself sits on top of a small pressure tank. The tank stores between 5-20 lt of water under pressure. When you turn on the tap, water is supplied from the tank until the pressure drops & the pump turns on, when the tank is full again the pump turns off. this means the pump runs for longer but with longer off periods in between & less pressure fluctuations.

A cheaper fix (bodge up) is to take a 3 inch blue plastic pipe (thick wall) about 2 m long, cap off one end, T it into the pressure outlet pipe from the pump to your house (useing suitable reducers) so that it is standing verticaly with the capped end at the top.

This will act as a pressure resevoir.

Good luck.

[Pond Life]

Oh, just an after thought.

If you go the cheap way, make sure you glue the end cap on the 3" pipe realy well, if air leaks out of the cap it wont work.

[Naam]

"Educate me Dr Nam tell me more are we talking about another tank or the one on top what do I need to do to fix it?"

******

one could forego the pressure tank and trigger the pump with a pressure switch only but this is not advisable. what the tank does is reducing the on/off cycling of your pump. bigger tank = less cycles. less cycles = enhanced lifetime of pump.

the pressure tank is not completely filled with water but (depending on the pressure your pump delivers) partly with water and partly with compressed air, the latter providing pressured water flow when the pump is in off-mode.

[Naam]

"I have looked at the pressure switch on the pump it looks to be sealed, now I am assuming the water pulsates because"

*****

macb,

you mention three pumps.

quote: "I have two pumps ITC pumps 1 pumps from the bore to the tank and 2 pumps under pressure to the house..."

what pressure switch of which pumps are we talking about? obviously not your well pump which pumps into the overhead tank. are the "two pumps under pressure" eqipped with a pressure tank? if not then your pulsating water is caused by on/off cycling of these pumps or if a pressure tank exists the pulsating water is caused by too narrow settings.

by the way, i have never heard of any sealed pressure switch because there must be a way to adjust the settings.

Edited January 28, 2007 by Dr. Naam

[old wanderer]

Maybe I can help here.

The pressure tank acts like an accumulator....as your pump turns on from the resevoir tank, it starts to build pressure, the diaphram in the pressure tank expands back and allows a quanity of water to accumulate in the tank until the pressure is great enough in the system for the pressure switch on your pump to shut off. (I used 30 psi on/ 42 psi off).

The head of air in the tank keeps water pressure in your house until you depleat the water in the tank and the pressure drops and the switch on the pump turns it on to recharge it again.

I had a tank at my ranch that was about 2/3 meter in diameter and almost 1.7 meters tall. I had a diesel generator for electricity, and could run my water in the house for some time before depleating this pressure tank, or needing to start the generator to run my well pump.

I had a large well pump, located about 100 meters from the house. I did not use a resevoir tank as my pressure tank acted as a resevoir and constant pressure supply.

Hope this helps....

Edited January 28, 2007 by old wanderer

[Naam]

The pressure tank acts like an accumulator....as your pump turns on from the resevoir tank, it starts to build pressure, the diaphram in the pressure tank expands back and allows a quanity of water to accumulate in the tank until the pressure is great enough in the system for the pressure switch on your pump to shut off.

wanderer,

your description of a pressure tank is correct but it does not apply to Thailand. i checked the specs of several suppliers and none of them have diaphragm tank. due to the local slim/high design the air bubble works just fine. the small disadvantage is that one cannot adjust the backpressure when the tank does not contain a diaphragm.

[macan]

Here's a link to the WELL resources website run by Water, Engineering and Development Centre, Loughborough University. http://www.lboro.ac.uk/well/index.htm

They are contracted by the UK international development agency to do research and development in water and sanitation with a necessarily 'low-tech', limited resources approach.

From the website you can get access to a lot of their reports, factsheets and technical briefs... good stuff!

[soap]

The drilling....I picked the spot.....he brought a two wheeled walk behind tractor with a front mounted centrifugal pump, suction and discharge hoses, steel screw together pipes (about 1.5 or 2 inch...I forget) and the couplings to screw them together, and a home made digging bit he screwed onto the bottom of the first section of pipe. The diggin bit just had some steel projections around it so that it could pulverize the dirt around it so that the dirt could be removed......there is no (or very few) large rocks in the ground here....some gravel but mostly very hard clay and clay with gravel. He use only water (no slurry). He puts the digging bit on bottom end of the first pipe and the discharge hose from the centrifugal pump on the other end and pumps water through this while it is held vertically so that soon the bit is sitting in a puddle of mud....he and his helper start to twist that pipe (and the bit attached) back and forth causing the digging bit to pulverize the dirt which gets washed out by the water being carried down by the pipe. The excess water is collected in a sump hole which he dug by hand (10 minutes work) about two metres from the bore hole so the water emerging from the borehole flows into the sump and the pump suction line takes the water out of the sump....so you can see that the water gets recycled....the dirt coming up from the well settles out in the sump and gets removed as needed. So...he just keeps rotating the pipe back and forth and the weight of the pipe puts pressure on the digging bit and as dirt is removed and washed out by the water flow around the pipe the bit and pipe sink lower and lower....when the pipe is all the way down then another section is screwed on and the process continues. He monitors the dirt as it comes up with the water and when it comes up with white sand he knows he's hit pay dirt...errrr pay water! So then he goes a bit further and he pumps some water out to see if there is enough flowing in....and.....there wasn't......so he says...."mai dee...I'll come back tomorrow and try again!"!!...only he says this all in Thai......and......sure enough he came back the next day and we hit a good supply of water and so he then installed the 3 inch pvc pipe which I supplied for the casing (linging).....3 inch is the largest diameter he will do. He put some verticle slits in the end of the casing at the level where the water bearing sand was so the water could flow in quickly and a piece of wood on the bottom to keep dirt from being sucked up I guess....I was kind of worried about the wood but he said that all his wells were done this way and it is no problem...so OK...

Chownah

i got a couple of thai guys in and so far they have done everything as in chownah post,hopefully they are coming back saturday to finnish the work,they have drilled down 21 metres to get sand/water,they inserted a 2 inch outer lining pipe then a 3/4 inch pipe witha valve on the end,

can anybody help with a doubt i have

(1) i have read that pumps can only pump up from i think 10 meters down,if this is the case do you have to put non returnable valves at different stages of the 21 metres and if so how many should i put in for the 21 metres

[chownah]

Soap,

Usually(often) when you drill into a sand layer filled with water the water will rise up inside the bore. If it rises enough then you can have a pump above ground to suck the water out. If it does not rise enough then you will have to put a pump down inside the bore to push the water out....having check valves every so often will not work. The water often rises to the level of the ground water (water table). This varies from month to month and place to place. I don't think that there are any pumps that can be placed down inside a 2 inch liner pipe....at least I have never heard of one but I could be wrong.

Chownah

[soap]

Soap,

Usually(often) when you drill into a sand layer filled with water the water will rise up inside the bore. If it rises enough then you can have a pump above ground to suck the water out. If it does not rise enough then you will have to put a pump down inside the bore to push the water out....having check valves every so often will not work. The water often rises to the level of the ground water (water table). This varies from month to month and place to place. I don't think that there are any pumps that can be placed down inside a 2 inch liner pipe....at least I have never heard of one but I could be wrong.

Chownah

hello chownah

this was going to be my second question but i forgot to add.

the water did come up the 2 inch pipe a few meters from ground level.

so with the 3/4 inch pipe do you still send it down to sand/water level or just send it down say about 8 metres

thanks for your reply

[chownah]

Soap,

Usually(often) when you drill into a sand layer filled with water the water will rise up inside the bore. If it rises enough then you can have a pump above ground to suck the water out. If it does not rise enough then you will have to put a pump down inside the bore to push the water out....having check valves every so often will not work. The water often rises to the level of the ground water (water table). This varies from month to month and place to place. I don't think that there are any pumps that can be placed down inside a 2 inch liner pipe....at least I have never heard of one but I could be wrong.

Chownah

hello chownah

this was going to be my second question but i forgot to add.

the water did come up the 2 inch pipe a few meters from ground level.

so with the 3/4 inch pipe do you still send it down to sand/water level or just send it down say about 8 metres

thanks for your reply

Assuming that you are going with a ground level pump sucking the water up I would send the 3/4 inch pipe down 10.5 metres. The absolute maximum that it is possible to even in theory suck water up in a tube (here on planet earth) is 10.33 metres so I would go a bit further because being longer makes virtually no difference and then for sure you know you have gone far enough. This 10.5 metres would be measured vertically from the highest point in the suction pipe to the inlet at its lowest point down in the well. I mention this because sometimes the suction pipe comes up out of the well and then goes down to the pump in which case you do not measure from the pump but from the highest point in the suction pipe which in this case would be above the pump.

Chownah

P.S. Running the suction pipe all the way to or near the bottom would work fine too only it would cost more for the pipe and you would have a bit of extra flow friction due to the extra length of pipe...a small amount for sure.

Chownah

[lingling]

I don't think that there are any pumps that can be placed down inside a 2 inch liner pipe....at least I have never heard of one but I could be wrong.

Don't know if it is available or if it would work, but one idea would be to use some type of ejector device down in the well and then a normal pump on ground level. The ejector can be made small enough to fit in a 2" pipe. Just an idea...

[soap]

thanks chownah,lingling for the info,

i have enough 3/4 inch pipe to go down to the sand but i will leave it up to the thai guys who are doing the job how far down they will go,at least i know now were they are going

thanks

[lingling]

I googled a bit on using ejectors in wells and that seems to be a common thing.

Something like this:

http://www.deanbennett.com/deep-well-vertical-jet-pumps.htm

[Lickey]

BOREHOLES

Lots of us have water boreholes and there are some of us who would like a water borehole.

But you get boreholes and you get boreholes i.e. some will work good & proper for a long time, and some will be nothing but trouble trouble trouble….because the borehole industry in Thailand, like all industries, has its "cowboys".

Some things you can do and some things to look out for when selecting the right man to do the job.

1) Jump in the pickup and drive around a bit – check out who else around you has a borehole and have a chat with them. Find out:

- how deep the hole is

- how much water it produces p/day

- is it year round (or if it changes, by how much does it change).

- what pump do they use (submersible or plunger type – down to around 10m you can get away with a plunger type, much further you're best off with a submersible, they are more expensive)

- how long has it been in use

- lastly, who bored it and what did it cost.

Check out as many as you can around your village/area – that will give you a realistic idea of what you can expect to get from a borehole on your land. You may even want to get a sample of the water and test it yourself for nitrates/nitrites/ calcium ect ect (done easily & cheaply). If its just for the house and garden 3 cubic meters volume a day is fine – which you can pump out with a couple of truck batteries if you have no ac mains power. Yup, so boreholes in rural areas do make a lot of sense.

Generally you have 2 sizes in Thailand: for domestic use you don't need more than a 6" diameter borehole, but for agriculture use and small businesses you want 12" diameter borehole (that's not to say 6" won't do – it can, and often does – just that you'd be better off volume wise if it was 12" diameter).

Check too if you need permission – some areas you'll have to go off and have a chat with the local Phu Yai (village head or District Head at the local district office, and in other areas no-one cares) – but check. The only time you'll get a "no" answer is if you're in an area that is surrounded by industry and the ground water is known to be not safe, or if there is a ground water quota in your area which is been exceeded (there some areas around Bangkok like that, where some industries lift large quantities of H2O from the ground, but out in the "sticks" I have heard of no restricted areas for quota based reasons).

Now's the time to have a chat with the guys who dig the holes – and to take note what you have been told by others, compare it carefully with what the borehole digger tells you – because they can tell some tall stories – for every 10 boreholes dug, at least half of them won't be serviceable after 5 – 10 years and its usually because they weren't dug properly in the first place, not because there isn't any water.

So what are the problems:

1) Slurry Slurry Slurry – other than fuel it's the boreholers biggest expense, but it's the most important component in boring. It will determine how long the borehole lasts and it will determine how many times you have to lift your pump to take stones out the impeller or indeed, replace your pump. The slurry is a mud that is injected down the hole and (because of its density) is used to lift all the loose dirt and in particular the stones, out of the hole as it is sunk. A lot of cowboy borers just do not use it because it cuts their expense. It must be used. It also ensures that the side of the hole are consistant – it will seep into the uneven side wall forming a consistant smooth surface which consolidates the wall and helps to prevent it from collapsing in over time – nothing worse than having a borehole wall that has collapsed in at 30 meters and compressing part of the tube wall – stopping you from retrieving your expensive submersible pump to get the stones out the impeller! So when you go round to see the guy (always best to go & see him first – and then follow it up with a meeting at your place), just look around his yard to see if there are slurry settling tanks lying around. If he uses slurry he'll have settling tanks lying around because they like to collect it as it comes up, let it settle and pump it back down again. No tanks then ask him if you uses slurry. If he says not needed, then move on. IT IS NEEDED to do the job properly – simple as that.

2) Borehole tubing –you get borehole tubing and you get borehole tubing. The cowboys will use the thinnest stuff they can get away with. Go check out the tubing yourself – get a quote from the boreholer, then ask him what the tubing costs, get that taken off and go get it yourself – so you know what's been used and get advise from the hardware store as to what is good tubing and what is not. Don't skimp on the lining.

3) Joining the tubes in the hole: 3 methods – threaded, screwed, pvc adhesive. Use screws and you are asking to be screwed. They will rust if not stainless steel, which will mean if ever you have to lift the lining you will not be able to. If not correctly screwed in they can break, or just as bad – as someone else has reported: they stuck through so far into the hole in his case they prevented him from getting the pump down the hole. The sharps ends can also wreck havock on the power supply cable in the hole over time. PVC adhesive would be a better choice, but again, it's adhesive strength can breakdown over time which again will prevent you from lifting the tubes if you ever need to. End threaded tubes are the best – they form a good tight joint and wont separate.

4) Dropping the pump: if using a submersible use 2 (TWO) stainless steel wire cables – not one. If one snaps you're buggered – try lifting a 10kg submersible from 30 meters on it's power cable. Not wise. Use two cables so you have redundancy and ensure they are stainless steel not normal multi-strand wire steel.

5) Who to use: well, I assuming you have been speaking to the locals who have boreholes and they have all had theirs done by the same guy and they have all been going for 5 or 10 years,, then I guess that's a fair bet. But failing that, and having understood all the above will be adhered to, what else: well, ask the guy if he has hydrology maps for your area. All the professionals will have maps and water table data for your area and will be able to tell you the mean, low and high water table levels for your area, season to season for the last 20 years – something that has been and is monitored very carefully by the authorities all over Thailand.

6) Get a good concreate cap poured around the borehole at ground level – and have a lockable cap on the top of the tube (to stop rubbish getting into the tube and someone nicking your submersible pump – they do get nicked).

How deep will your borehole have to be – well, about as deep as those around you who have boreholes, but there is no average – each area, depending on its elevation above sea level will have its water table at a different height relative to the surface – and will be affected by the geology of the region. Some areas are as shallow as 6 – 10meters for good all year round water supply, and in other areas (like where I am) you have to go down 80 – 100 meters to get year round water. Clay areas shallow, chalky areas deeper, and the deepest boreholes are found in the sandstone and granite areas – which also give the best water as the sandstone acts as a brilliant filter. Chalky areas make the water real hard with calcium.

If anyone has their own "borehole experience" to add – go ahead.

Tim

Hi Tim, thanks for all the infomation on boreholes, very interesting reading, I would like your advice on some options i have, firstly we have a borehole with a submersible that pumps about 10 gallons a minute, enough for 1 sprinkler over a 20 mtr radius, apparantley the hole is 30mtr and even now in dry season keeps going all day, it has to pump water uphill 200mtr and irrigate 9 rai of papaya, and in the next few weeks want to plant 6 rai of banana, its a red clay soil and seems very water retentive, the borehole is 12inch, delivery pipe is blue 2inch, picking your brains now, is it possible to make exsisting hole deeper? or/and get a bigger pump? thanks for any advice you can give, Lickey..

[RasiMike]

Here in Issan, (Rasi Salai) we put in a 26 + metre bore, hit ('naam') at about 15 or so.... Total cost with 100 mm casing ......3840 baht (3000 + Laos Khao quart yai neung). I pump continuously for approx 3 hrs/day and no problems over 2+ years. The water quality is a little suspect (odour) .....however the father-in-law, Pho yai etc. have no complaints about the Papaya, Phak,...Khoi? (banana), Tangmoor etc....... not to mention the size of our ducks. Drinking water comes from the roof .Perhaps the estimates posted on this thread may be due to the Farang factor or "geographical positioning"......... Or perhaps very good Thai-in-laws in my case?

[palm]

My Thai project manager was just quoted 120,000 baht for:

9" bore-hole

up to 100m deep (they said 50-70m is probably what we'll end up needing)

including submersible pump and motor etc

screw-together tubing

10% deposit

40% on completion and working after a few weeks

remaining 50% after 12 months if everything is still ok

will take about 10 to 20 days to do unless they hit a ton of granite (same price, their hard luck)

Location is Phitsnulok. Seems quite a fair deal to me?

I have about 120 rai to supply, and new lakes to build/fill etc.

[RamdomChances]

^ Palm, I think I paid 70-80,000 for mine, 6" hole, 2 hp pump can do about 10,000 l/hr all the fittings ect, it's about 60m but this is a few years ago.

Rasi mike, thats a remarkable low price, you can't buy a pump for that