Underground Watertank

[Neeranam]

I'm building a house and it's time to buy a water tank. I had an idea to put it/them underground. I might buy 2 of them.

Are there any advantages/disadvantages I should know about?

Would I need a stronger pump? Thanks.

[xen]

Just some bullet points from my experience in this area.

• What size (litre) are you contemplating? This will have an influence on what the tank will be made of - plastic, gal iron , concrete.
• Will you be rain harvesting off your roof or town supply? Can harvest rain water straight off the roof
• If you bury the tank completly you will still need to install the tank on a concrete pad .
• You also need to decide if will need either volume or pressure from your pump if you are pumping from tank to house . This will also influences your pipe sizes.
• If you use underground tanks then Grundfos makes very good submersible pumps that sit just of the bottom of the tank floor.( I have used these for irrigation systems on sporting fields and seem to be the most efficient.)
• If you bury your tank you will get considerably less evapouration and your water will be cooler.
• if completly burried then no "ugly " tank to be seen
• There is the extra cost for excavation and plumbing .
• You should have extra life on burried tanks but is it worth the extra cost.
• There are some very innovative but expensive under pavement type tanks (Alantis is one company but not too sure if available in Thailand) that may be worthwhile looking at depending on your needs and budget.

Hope that is of some help

Edited March 14, 2013 by xen

[craig]

I have an underground cistern. Bought a number of the premade concrete "rings" (large size). Dug a large hole, poured a cement floor, placed the rings in, then put a coating of cement 'plaster' on. I opted to have the last few rings above ground making a platform.

Installed a pump. It is working fine now for five years...water kept cool by the earth.

I have separate tanks to catch water off the roof (installed gutters).

[Langsuan Man]

Think about cleaning an under-gound tank ? Because believe me you will be cleaning your tank within a year since water here in Thailand is incredibly dirty

Once you "bury it" will you be able to access it with heavy machinery if it has to be dug up ?

Yes, you will absolutely have to have a pump if underground. An above ground tank will still provide a minimum amount of pressure for toilets and maybe a sink when the electricity goes out

But as said many time here: up to you

[Neeranam]

Just some bullet points from my experience in this area.

• What size (litre) are you contemplating? This will have an influence on what the tank will be made of - plastic, gal iron , concrete.
• Will you be rain harvesting off your roof or town supply? Can harvest rain water straight off the roof
• If you bury the tank completly you will still need to install the tank on a concrete pad .
• You also need to decide if will need either volume or pressure from your pump if you are pumping from tank to house . This will also influences your pipe sizes.
• If you use underground tanks then Grundfos makes very good submersible pumps that sit just of the bottom of the tank floor.( I have used these for irrigation systems on sporting fields and seem to be the most efficient.)
• If you bury your tank you will get considerably less evapouration and your water will be cooler.
• if completly burried then no "ugly " tank to be seen
• There is the extra cost for excavation and plumbing .
• You should have extra life on burried tanks but is it worth the extra cost.
• There are some very innovative but expensive under pavement type tanks (Alantis is one company but not too sure if available in Thailand) that may be worthwhile looking at depending on your needs and budget.

Hope that is of some help

Great help, thanks for taking the time.

I don't know anything about size, but there's me and the wife, 2 kids and 2 dogs to supply. Any suggestions?

We live in the city(Khon Kaen) so the water doesn't go off much - sometimes between 10 and 4 but never for more than 2 days.

Volume or pressure? I don't understand.

[chiang mai]

There's a number of water usage calculators available on the web that should get you close to your usage.

[Neeranam]

chiang mai, on 15 Mar 2013 - 10:57, said:

There's a number of water usage calculators available on the web that should get you close to your usage.

Thanks

120,000 litres a month. Surely this figure will depend on how many days you are without water.??

[Neeranam]

Langsuan Man, on 15 Mar 2013 - 10:42, said:

Think about cleaning an under-gound tank ? Because believe me you will be cleaning your tank within a year since water here in Thailand is incredibly dirty

Once you "bury it" will you be able to access it with heavy machinery if it has to be dug up ?

Yes, you will absolutely have to have a pump if underground. An above ground tank will still provide a minimum amount of pressure for toilets and maybe a sink when the electricity goes out

But as said many time here: up to you

Good point, thanks.

[Neeranam]

craig, on 15 Mar 2013 - 07:46, said:

I have an underground cistern. Bought a number of the premade concrete "rings" (large size). Dug a large hole, poured a cement floor, placed the rings in, then put a coating of cement 'plaster' on. I opted to have the last few rings above ground making a platform.

Installed a pump. It is working fine now for five years...water kept cool by the earth.

I have separate tanks to catch water off the roof (installed gutters).

Thanks - do you have to clean the tank?

What about if you have a filter going into and out of the tank?

[chiang mai]

The parts of the conversation of five/seven years ago here on this subject that I remember are as follows:

You need to build some hellishly big tanks if you want to reply on rainwater as a sole feed and to store enough for year round use, best bet is a combination of rainwater stores for x months topped up by municipal supply.

Building undergound storage tanks out of block with skim coat is cheaper than buying plastic tanks, BUT, is only sensible to do if multiple linked storage tanks are involved else the sheer size of a single tank makes it a major engineering project which is beyond most people.

You perhaps might want to search the forum for this topic, it's been done several times.

[xen]

Just some bullet points from my experience in this area.

• What size (litre) are you contemplating? This will have an influence on what the tank will be made of - plastic, gal iron , concrete.
• Will you be rain harvesting off your roof or town supply? Can harvest rain water straight off the roof
• If you bury the tank completly you will still need to install the tank on a concrete pad .
• You also need to decide if will need either volume or pressure from your pump if you are pumping from tank to house . This will also influences your pipe sizes.
• If you use underground tanks then Grundfos makes very good submersible pumps that sit just of the bottom of the tank floor.( I have used these for irrigation systems on sporting fields and seem to be the most efficient.)
• If you bury your tank you will get considerably less evapouration and your water will be cooler.
• if completly burried then no "ugly " tank to be seen
• There is the extra cost for excavation and plumbing .
• You should have extra life on burried tanks but is it worth the extra cost.
• There are some very innovative but expensive under pavement type tanks (Alantis is one company but not too sure if available in Thailand) that may be worthwhile looking at depending on your needs and budget.

Hope that is of some help

Great help, thanks for taking the time.

I don't know anything about size, but there's me and the wife, 2 kids and 2 dogs to supply. Any suggestions?

We live in the city(Khon Kaen) so the water doesn't go off much - sometimes between 10 and 4 but never for more than 2 days.

Volume or pressure? I don't understand.

The difference between volume and pressure is , can i illustrate that if you have a hose and the water will just drop out the end of the hose but you will get volume but if you put your finger over the end you will restrict the volume but the pressure of the water will shoot maybe a couple of meters or more. . So if you need to fill another tank you would usually use a centifugal pump which works like a water wheel inside a casing to put it very simply but if you need to push the water further then another type of pump will be required.

The size of your tank will be determined by the amount of roof you have if you are getting water from your roof. here is a good site to get your calculations from http://www.bushmantanks.com.au/calculators . This is because if you can't fill a big tank it is a waste to get that size and if your tank is too small then the water you could be collecting is escaping. Then, after that calculation , look at your usage .

Craig's idea about the concrete rings is a very good and cheap way of doing it . I have only used either plastic or custom built concrete tanks but they are expensive.

And Langsuan Man is right too , you will need to be able to clean them . Tanks can be dangerous places if you enter and not careful and we always use people with confined spaces certification altho i doubt if you will find anybody with that around your area but do take care when you are getting in there to clean it. Make sure you use at least a buddy system .

To restrict the need for cleaning somewhat is to run you water off the roof with a first flush system between the roof and the tanks ( google for info on them) and then make sure the water goes thru a couple of filters. But it will not remove a lot of other chemicals like iron or allums etc .

Also the idea of using linked tanks is good too especially if they are linked by equaliser pipes so the level remains equal in all your tanks .

Best of luck with it .

[Pacificperson]

I have heard that empty tanks in flooded earth can pop up like corks. So, you probably don't want to bury them if you are in a high ground water area.