A different water pump problem

[BuriRamHome]

Recently had fitted a deep well pump (Hitachi) about four months ago. It was in a temporary location while building the house and now the house is finished we have moved it close to the water tank, about four meters from bore hole. The problem is that it will no automatically fill the tank, when the sensor float activates the pump, it starts but does not pass water to the tank.

We unscrew the plastic plug and fill the pump chamber with water, several litres, replace the plug and switch on the power again. Often we need to repeat this four of five times before the water is flowing.

The installer said it was either a faulty pump, to too far from the bore hole, which is Thaispeak for 'I don't know what s wrong"

My friend has similar pump more than 2 meters from the borehole and has no problems so I am thinking that our short distance should be no problem.

It is a pain manually starting this pump everyday.

Any member had a similar problem and can help with advice before I resort to buying a new pump.

thanks

[Pib]

From your description you are losing prime (as you know). Could very well be a bad/dirty "footer" valve in the bore hole letting the pump prime leak back into the well.

[lopburi3]

Poster says deep well but seems to indicate he is using a shallow well pump - what is the pump spec/model number? How deep is the water in your well? What works for someone else does not equate to working for you as your well water can be a very different levels.

[Pib]

Could be...so many different type pumps...some loosely decribed as deep water well pumps. Below is a deep water well Hitachi pump which uses two pipes going down the well hole to a jet assembly like shown in the second image below. Yeap, he needs to better identify his pump model and setup clearer.

[NickJ]

When you prime the sump does it pump the water out?...... if thats the case the valve that opens when water is being pulled from the well is staying open.....

[ericthai]

you defiantly have a priming issue. As mentioned above most likely the foot valve.

[DirtyDan]

These pumps are not designed to "pump" air and needs to be full of water before they can move additional fluid (called prime) - the fact the pump works after you fill the chamber is proof it's a priming issue. Moving the pump far away from the borehole could possibly affect the pumps suction capability, but a couple of feet is not enough and that's why there should be a valve at the bottom of you well (the foot) which keeps the suction lines all full of liquid.

So, how is it your pump is losing the fluid when it stops pumping? Likely culprits:

1) the foot valve (in the well itself) is not working which allows the water to flow back down the well when the pump is turned off.

2) the new connections in the suction line were not put together properly allowing air to be sucked into the chamber when the pump is operating or allow water to leak out of the suction line when the pump is off.

3) your well goes dry while pumping and the pump is sucking air in from the bottom of the well (water is not flowing into your well as fast as you're pumping it out).

Edited June 26, 2015 by DirtyDan

[moojar]

BuriRamHome, I have nothing to add, as I know nothing about pumps. Hope it all works out for you.

I will be building in Buriram in a few years however, so would be interested to hear who the "Thaispeak" installer of your pump is. To possibly help me choose who to purchase from when my turn comes.

Ta.

[PattayaClub]

Not enough information to even guess. Pumping is a very complex science. It is also quite logical -- if you understand it, and have all the facts.

[Yme]

The pump should be as close to the water source as possible. The maximum distance between pump and foot valve without an injector system is around 8 metres.

As others have said, check your foot valve also.

Pumps are great squirters, but poor suckers.

[BuriRamHome]

Thanks for the info guys.

Some more information, we have disconnected at the top of the bore hole, and there is water in the pipe coming out of the bore, and it does not drop in level, so thinking the foot valve is OK

Water does not go dry before pump has finished filling the tank, so think there is plenty of water to draw.

Two pipes run from the bore to the inlet side of the pump which is Hitachi DT-P300GX

The two pipw jet assembly appears to be 30cms above ground and a single pipe as the bore hole pipe, wondering if thus is correct, although this is the same as other set up in local houses.

The installer still does not know the answer, even though he was here for several hours again today.

Thanks in advance.file:

Edited June 28, 2015 by BuriRamHome

[PattayaClub]

You know, you cannot get anything but guesses if you do not supply ALL the information. How deep is your well? What is the static level? What is the water production rate of your well (recovery rate)? At what level is your foot valve? What is the size of the well casing? What is the complete pump model number?

Check your pump specs. You did not say whether you have the SJ or the PJ model. They have different specs. The max lift for the PJ is 30 meters and the max for the SJ is 18 meters. If you exceed that, then the pump will run, but no water will flow.

Without all the facts, let me offer a guess. Let's assume a sample well. The well is 40 meters deep. The static level is at 30 meters (ten meters from surface). The well has a recovery rate of 8 liters per minute. Your foot valve is at 35 meters. The casing is 4" (10cm). The casing hold 12.7 liters per meter actually less because of suction pipe displacement). You are filling a 4,000 liter tank. You have a Hitachi DT-P300GX PJ.

That model pump can (theoretically) produce 9 l/m @ 30M, 16l/m @24M & 20 l/m @ 18M. For flow calculations, You are pumping, NOT from the bottom of the well, but rather from the water level in the well -- the static level. So you begin pumping with suction from 10M, and can produce 20 l/m. The distance from the static level to the foot valve is 25 meters, so you have a 197 liter reserve. But since your pump can only lift from 30 meters, your recoverable reserve is actually only 157 liters.

You are trying to fill the empty tank. You start out pumping 20 l/m. Since the recovery rate is 8 l/m, you are effectively lowering the static level by 12 l/m. So in 9 minutes the static level has dropped 14 meters from 30 meters (ten meters from surface) to 16 meters (24 meters from the surface), and you have pumped 180 liters of water. The pumping rate will drop to 16 l/m since the static has dropped. At this point you will lowering the the static level by 8 l/m.

You get the idea and can do the rest of the math. I know nothing about your well or what your pump model is. But it if you have the SJ model and trying to fill your tank, you pump the static level of the well down to 18 meters, the pump will stop lifting. It will run but no water will flow, as it has reached its lift capacity. Ditto for the PJ model if the static drops to 30 meters.

So this could be your problem. But without significantly more data, you are pissing into the wind; you will never know for sure what the answer is.

On the other hand, you say you need to repeatedly "prime the pump" each time before it starts, but you also say that the foot valve is holding and the bore pipe remains full of water. This just doesn't make sense, unless the foot valve is leaking slowly enough that you still have water in the bore pipe, but it has drained from the pump. The farther away from the bore your pump is located, the more likely you could find this scenario. There could be a little sand or small pebble in the foot valve.

Is there a slow leak? When you said you uncapped the bore pipe and "the water did not drop in level," was that while you were watching, or did you let it set that way for 24 hours then go back and have another look to see if it dropped?

Look at Pib's diagram. Normally for a jet pump there are two pipes going down to the foot valve (diagram on left). A pump cannot suck very far (10.3 meters is the max). A jet pump uses a prime to get it going and pumps water DOWN the well then uses a venturi to suck in more water and push it back up to the surface. So it is not "sucking"; it is pushing.

You probably could have avoided all this by using a submersible pump instead of a jet pump. They are more efficient, too.

But, with all due respect, you probably listened to a Thai "expert." No Thai would ever do the calculations shown above, but ANY western expert would do these calculations BEFORE recommending or sourcing a pump. Don't feel bad. I stupidly listened to an expert when he told me that 100 meters of 2.5mm2 cable would be fine for my 2hp submersible pump (drawing 15 amps). I normally do all my own calculations, but since this was a "pump guy," I drpped my guard and just believed him for some reason. It resulted in a 20 volt drop over the line and the pump control kept shutting down the pump. I figured it out, did the calculations and fixed it, but it cost me.

When you are dealing with complex matters like pumping, friction and velocity loss over a run of pipe or voltage drop in an electric wire, if you want a perfect job, you MUST educate yourself by spending 100 hours on the Internet (or whatever it takes), and then do the calculations and work yourself. I have never gone wrong by doing this, I see farangs everywhere getting screwed because they don't.

Keep in mind the difference. A farang wants the job to be done right. He wants everything to work as planned. In your case, a Thai would be perfectly happy if the tank could only be filled half full. He'd just run the pump twice as often. So you see, for a Thai, the installer did a good job. The installer probably cannot understand why YOU have a problem. It's the culture.

[BuriRamHome]

Thanks for all the replies, I have learned a lot more about wells and pumps.

Cured my problem very simply in the end: changed the electric float valve to a standard ball float valve and now it fills automatically.

Not happy with the ball valve type as it means the tank refills a little every time we draw water, the electric float would only top up the tank when it got three quarters empty, say one per day, less electricity and less wear and tear of the pump.

Dont understand why the pump only works with the ball valve, does anyone know if I need a different type of pump to be able to use the electric float, maybe a submersible pump, but the well is 30m deep.

[PattayaClub]

Thanks for all the replies, I have learned a lot more about wells and pumps.

Cured my problem very simply in the end: changed the electric float valve to a standard ball float valve and now it fills automatically.

Not happy with the ball valve type as it means the tank refills a little every time we draw water, the electric float would only top up the tank when it got three quarters empty, say one per day, less electricity and less wear and tear of the pump.

Dont understand why the pump only works with the ball valve, does anyone know if I need a different type of pump to be able to use the electric float, maybe a submersible pump, but the well is 30m deep.

I use an electric float switch to avoid the on/off problem you describe. It works fine, starting the pump when the water level in the tank falls to a predetermined level, then turning off when it fills to the predetermined "off" level (just before the ball float valve, which remains for safety).

I know this is probably a silly question, but are you sure you had the float switch wired correctly and that it was working? Might the float switch be defective? I mean a switch is a switch. A float switch will turn a pump on and off the same as any other switch. The type of pump should not make any difference at all. With every one of them you are turning and electric motor on and off.

[BuriRamHome]

The float switch worked fine, no problems, when the level dropped it switched on the pump.

Problem was that the pump did not hold the water and needed to be primed overtime.

It seems like the hitachi pump with ten jet needs to work off a pressure switch rather than an on/off electrical switch.

Now there is pressure in the pipe leading to the tank the problem is solved.

[Crossy]

I wonder if the non-return valve has a weak/no spring, it's been reported that some installers remove the spring completely to make it work "properly".

The added pressure in the pipe ensures the valve closes completely (which the spring should do).

[PattayaClub]

I wonder if the non-return valve has a weak/no spring, it's been reported that some installers remove the spring completely to make it work "properly".

The added pressure in the pipe ensures the valve closes completely (which the spring should do).

When I had my well drilled and submersible pump installed, I saw the installers pounding and beating a small disk out of the top of the pump. I wondered what the hell they were doing and asked. They said they had to take it out. I thought at the time that maybe it was a protective cover of some sort, but wondered why such a thing would have to be violently beaten out. I did not realized until later that they had removed the check valve -- VERY BAD!

With the check valve gone, if the pump goes off, the water is draining back into the well spinning the impellers in reverse, then the pump comes back on, it could damage or destroy the pump as the impellers rapidly reverse direction.

I suspect they remove the check valve because with it, a very heavy column of water remains in the PVC pipe going down the well. They had no hist and lowered the pipe by hand, and would have to pull it back up by hand to remove it. Their solution: Take out the check valve. Another stupid Thai plumber trick.

I know now that there should actually be a check valve in the pump, another put in the column above the pump and still another no more than 25 feet above the static water line, and another every 200 feet. My well, however, is only 28 meters.

I put a check valve in at the well head, but there are only two kinds of check valves: Those that leak and those that will leak. Which I guess is better than nothing. BUT, I could be very wrong, because when there is a single check valve at the top, above ground, when the pump goes off, there is going to be negative pressure in the pipe going down the well. As the check valve leaks and the water column drops, the negative pressure is in an air column. If the pump comes on at this time, the pump is going to start spinning way to the right of the pump curve, and WHAM! I am going to get a giant water hammer. What I would like to do is wring the neck of the guy that took out my check valve, then slap him around a little. There is no question that the life of my pump was shortened.

As for the need for back pressure to avoid losing your prime, I can understand that. I had to take apart and clean the internal check valve on my Hitachi constant pressure house pump. It is NOT spring loaded and operates by water pressure alone holding it closed. So, with a well, I can see that if you simply cut power to the pump, the check valve would relax and the water would bleed out of the system. But one would think the foot valve would stop the back flow -- unless it is leaking (but they all probably leak a little). You could also try putting some more spring loaded check valves in the line.

Edited August 12, 2015 by PattayaClub

[PattayaClub]

There is a very informative discussion of check valves in well systems here:

http://terrylove.com/forums/index.php?threads/submersible-pumps-and-multiple-check-valves.26301/