New well pump not working...

[simon43]

This morning our well was almost dry, so I took the opportunity to pull up the submersible pump that pushes the well water to our ground-based, 2000 litre holding tank.

The old pump was looking well past it's best, so I decided to buy a new pump of the same specification - capable of pumping to a height of 12 metres.

I prepared the new pump, attached the pipe, ropes and power cable, and lowered it down to the bottom of our well which had now collected about 40cm of water from last nighut's rain.

However, when I switched on the power, the pump failed to pump water up to the holding tank...

I lifted the pump up and placed it in a tank of water at ground level. It pumped the water fine.

I lowered it down the well again to the same depth as the old piump and it failed to pump the water, although I can hear the pump impellor etc turning.

The pump is not in silt at the bottom of the well - it still looks quite clean.

So I am beginning to think that this new pump is unable to push water to the stated height of 12 metres, although the label on the pump states this, and is identical to the old pump which worked fine.

Any suggestions? Would it help to reduce the size of the water pipe that carries the water up from the pump? The new pump is fully submersed in the 40cm of well water, so I cannot see that being the problem.

Have I been sold a lemon???

[Crossy]

I've had submersibles (pond not well mind) sit in 3 feet of water and just gurgle, problem, trapped air, how to get it out of a well pump I know not I'm afraid.

Any way of back-flooding the pump from your tank to get it going?

[simon43]

Having checked up on fluid dynamics etc, It could also be that the pipe I'm using is too small. The pump discharges into a 2 inch outlet and I'm using the pipe from the old pump which is just about half an inch ID.

I will go and buy some 2 inch clear pipe and test with this....

but you could also be right about trapped air etc. I'll try to back-flood it......

[Ruin]

Trapped air is a hassle in our pumps. I have a T joint in the pipes with a valve. The T is upside down. Open the valve, pour water in until no more can go, turn the valve shut, turn the pump on and voila.

[jacko45k]

Trapped air is a hassle in our pumps. I have a T joint in the pipes with a valve. The T is upside down. Open the valve, pour water in until no more can go, turn the valve shut, turn the pump on and voila.

That is good..... I have tied a rope to the bottom of the pump before so that I can jiggle it while it is down there to get the air out.

The clear pipe is good too, you can see how far up you are getting, and maybe lower the high end to that height until water flows then raise it again.

Edited April 17, 2014 by jacko45k

[impulse]

Try reversing any 2 of the 3 leads if it's a 3 phase pump.

It sounds like it's running in reverse. You have a 50-50 chance of getting it right the first try.

Edit: A centrifugal pump will pump fluid in reverse rotation, just not as much and not as high.

Edited April 17, 2014 by impulse

[rafish]

You need to "prime," the pump as mentioned previously. Fill the discharge line full and force the air out. Your pump will work fine I think after that.

[maswov]

Reducing the size of the pipe will cause more resistance and have the opposite effect of what you want.

[cdmtdm]

increase the pipe size 50 % of the way first , so 2 inch out of the pump put on two lengths ( 8 m) then reduce down to 1inch or 1 1/4 inch ... the calcs are done on the same size as the discharge of the pump ... is it a standard sub pump the same as used in a pond or water tank ? or is it a deep well type sub pump, long skinny stainless unit that slips inside a 6 inch pvc ?

[simon43]

I bought some 2 inch clear pipe and attached that to the new pump. Now the pump raises the well water just to the ground level, but is unable to raise it a further 2 metres to empty into the holding tank.

So it sounds like this new 12-metre head pump is not really working to the spec, (or the old 12-metre head pump exceeded it's spec...)

To prove my theory, I went and bought a hefty, submersible pump with a 16-metre head and attached the small diameter pipe to it, (the 2 inch pipe was hard work to handle..).

Voila! - The 16-metre head pump works just fine. I'll keep the 12-metre (probably really 11-metre) pump for other uses - they are not that expensive.

Simon

Edited April 17, 2014 by simon43

[gimbo2]

its dead easy to check pump head.

You say 12 mt so get 12mt of same size pipe as pump outlet sit in a big bucket of water and start pump.

If it pushes water out the top of the 12mt pipe then the pump is ok.

if pump is ok maybe try putting it further down the well, maybe just maybe your water level is lower than you think/

[Crossy]

Part of the problem is that the Max-Head shown on the pump is at zero flow, so a 12m pump will (just) pump water to 11.9m (I have that T-shirt).

If you get on the manufacturer's website there should be a set of flow / head curves to show what flow you should expect at a particular head. There will also be a point at which the best flow / head combination occurs, you should choose your pump so that the actual head your pump sees is close to that point (don't forget that head includes pipe friction).

[lucifer666]

Trapped air is a hassle in our pumps. I have a T joint in the pipes with a valve. The T is upside down. Open the valve, pour water in until no more can go, turn the valve shut, turn the pump on and voila.

Yup, this was the solution that sorted out the same problem for me.

[Ruin]

Ahhhh, anyone remember Tim the toolman Taylor. More power!

[Canada]

Never heard of having to prime a submersible pump.

[Crossy]

Never heard of having to prime a submersible pump.

Neither had I, until I had a (pond) sub that wouldn't pump as the depth of water was insufficient to push the trapped air out through the check valve.

Tipping the pump on its side let the air out and pumping started.

[callaway]

Any submersible over 1 will pump 12 metres open flow. The problem you have is that at 40cm water the static water level would be lucky to be high enough to reach the intake of the pump, between motor at bottom and pump at top. Even if it did it would draw down the water level below intake on start up of pump. Basically at 40 cm you do no have enough water in the bore. To check use a string line with a weight on it. You will hear when it his water and bring it back up and jiggle while lowering and you will determine your static water level. Then lower to bottom and if still 40cm then your problem is solved. Not enough water depth in your bore. Submersibles do not have priming problems,unlike centrifugal pumps. They sit in water and pump from there. Meaning no air locks or priming issues. Have worked water boring and pump installations for over 20 years. Just a footnote to let you know that I know a bit about pumps. Asstated by another,if it is 3 phase, which i doubt in Thailand, you ca swap over any 2 of the power wires at the contactor to reverse the motor. But you proved it was ok by running it in a tank.

[Ruin]

Another option is to have the pipe go down to the water and the pump up top. I have this on one well and being able to service the pump easily is very handy. I am using a hitachi, don't have the numbers to hand, i'm at wirk, rectangular white casing, quite quiet, reliable, easy.