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Submersible pump - Why no Pressure Reading?


carlyai
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My 0.5 HP submersible is pumping fine, but I can't see a pressure meter reading on my guage. It doesn't move of zero. I think I read the pressure should be about 20 psi.

I know there is water pressure there because I installed a 3 m  pipe vertically and the water flow out the end was fine (to eventually connect to fill out tank).

I know I'm missing something basic but I can't see it.

Sorry pics stuffed up.

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Just a thought: What does that pressure sensor show?

The pressure difference on one side of the sensor compared to the other side of the sensor?

Or the pressure in the pipe compared to the outside pressure?

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Blockage on the input to the gauge from the main pipe?

is the gauge working?  try air pressure to the input of the gauge; even blowing hard might get some movement of the pointer.

Water flowing out of 3m high pipe will only need about 2 psi.  I would expect to see a jet of water really blasting out of the pipe.  Something blocking the input to the pump, or stopping to rotating.

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29 minutes ago, Robin said:

Blockage on the input to the gauge from the main pipe?

is the gauge working?  try air pressure to the input of the gauge; even blowing hard might get some movement of the pointer.

Water flowing out of 3m high pipe will only need about 2 psi.  I would expect to see a jet of water really blasting out of the pipe.  Something blocking the input to the pump, or stopping to rotating.

Thank you. It would seem the pressure is about 2 psi then. It's definitely not exactly blasting out, but hopefully enough to get up to the tank and fill it.  Thanks again.

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46 minutes ago, OneMoreFarang said:

Just a thought: What does that pressure sensor show?

The pressure difference on one side of the sensor compared to the other side of the sensor?

Or the pressure in the pipe compared to the outside pressure?

It's the meter not showing pressure. I think Robin has the answer in that the pressure is low.

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When I looked at the pump curve at about 40 m the flow rate was 20 LPM , so that was what I was looking at. Because I don't know that much about water I equated 20 LPM to a reasonable pressure, or a reading on my pressure meter, but now thinking about it, and comparing the pressure from the submersible to the pressure from the house pump, I notice the difference. Anyway, problem solved and 20 LPM is fine at about 40m. 

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I just remembered 1 bar = 10m lift height, so to my tank about 0.5 bar of low pressure water. So my meter will hardly move. I need a meter with 100% deflection of 1 bar, but I'm not fussed.

 

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10 hours ago, farmerjo said:

Check your pump curve and do a bucket test if you want to get technical.

 

Apologies,up to early this morning and missed your post about pump and flow.

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If it is a mechanical pressure gauge (C tube Bourdon)......try giving a good knock.....they tend to be a bit sticky when new.

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10 hours ago, carlyai said:

I just remembered 1 bar = 10m lift height, so to my tank about 0.5 bar of low pressure water. So my meter will hardly move. I need a meter with 100% deflection of 1 bar, but I'm not fussed.

 

Nominally 10m is equivalent to 1 bar or 14.7 lbs/sq inch. If you are lifting the water up 30 feet or about 10m allow 1 bar plus an extra 0.5 bar if you want a good water pressure out of it

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12 minutes ago, Will B Good said:

If it is a mechanical pressure gauge (C tube Bourdon)......try giving a good knock.....they tend to be a bit sticky when new.

Not the ones I used to make.😉

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5 minutes ago, VocalNeal said:

Not the ones I used to make.😉

I must have got the other guy's.....555

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5 minutes ago, Will B Good said:

I must have got the other guy's.....555

The cheap ones don't have a jewelled movement.🤫

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  • 2 weeks later...
42 minutes ago, Yellowtail said:

How deep is the pump? That is where the maximum pressure will be. 

 

 

I think I'm ok   got the pipes connected to my 3000L tank and got a good water flow into tank at a height of 4m. The bore is around 56m but the pump is at 16m inside casing all the way.

I'm presently painting the roofed area made to cover the pump and other electrical boxes.

Just bought all the NYY cable for the pressure and pump electrics. Pump box made up already and tested.

Few more days painting etc and should be all set to change over from our existing bore. Hate painting.

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Pump box completed and bench tested.

Got a tap on a pressure switch and a float switch in my water tank. I can't set the pressure switch and float switch to both turn the pump on, so pressure switch drives a relay whose contact can operate the pump like the float switch. So I've got these two contacts in parallel. So either contact making should start the pump. I have a non-return valve after the pump and pressure guage.

Not sure of how much water will want to flow to the tank when I open the tap connected to the pressure switch.

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On 6/20/2022 at 5:53 PM, OneMoreFarang said:

Just a thought: What does that pressure sensor show?

The pressure difference on one side of the sensor compared to the other side of the sensor?

Or the pressure in the pipe compared to the outside pressure?

Yes that is quite a thought especially after seeing the photos.

 

The pressure difference on one side of the gauge compared to the other side of the gauge is zero.  The pressure is the same on both sides. See the straight pipe the gauge Ts off from.  The water does not flow through the gauge.  

 

The pressure gauge does not measure or input outside pressure, it just measures pressure in the pipe.  

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I cant see if gauge is in barg or whatever, i assume it is 10 barg, over pressure from static pressure (pressure in atmosphere). another gauge is doing in bara, which means from absolute zero (vacuum) and makes no sense in a pump pressure measuring.

You say you go up 4 meter, so that pipe full of water generates a pressure on the meter of about 0.4 barg. Pump is not running and it is full of water.

Maybe you remember P= height(meters) x Rho (density of water= 1000 kg/m3) x C ( a constant of 9.81) / 100000 (to get from N/m2 to Bar).

The meter doesnt show, so pipe is empty or meter is not working. You took of the protection of the thread or inlet of meter or is there any other blockage? Or meter has a major offset due to falling or bumping it to hard. In the back there could be a zero adjustment screw, as i see it is not on the pointer. Otherwise meter is broken.

Probably you also over estimate the pressure by pump?

The pump brings it up from 3 meters down the well and then up to a tank 4 meters, so thats a loss of 7 meters.

You have a pump curve, is that given in meters or does it maybe say feet? 40 meter is 4 barg tops with almost no flow, but 40 feet = 12 meters= 1.2 barg, then going up 7 meters, so leaving 1,2 - 0.7= 0,4 barg, when running, and should be showing on meter, when that one works. This is only going straight up, however you also have losses due to used pipe material, bends, valves, filters, viscosity, temperature and so on. 

 

IF you only use the pump for filling your tank, you dont need a pressure switch to control on/off. The level switch would be the only one for controlling. You use a pressure switch if it is also used with a water system with valves in it, opening and closing. A valve closes, pressure goes up and switch off the pump.

In case of ONLY filling up tank, you need only level.

Unless you like to protect tank and you have a pressure switch to switch of the pump, in case the level meter wouldnt switch off. However again if tank is not closed and is open to environment, it is useless. It will just overflow then.

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4 hours ago, bignbad said:

There will be no significant reading if pumping to an open ended pipe!

 

That would depend on how much higher the open end of the pipe is than the gage, yes? 

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1 hour ago, xtrnuno41 said:

I cant see if gauge is in barg or whatever, i assume it is 10 barg, over pressure from static pressure (pressure in atmosphere). another gauge is doing in bara, which means from absolute zero (vacuum) and makes no sense in a pump pressure measuring.

You say you go up 4 meter, so that pipe full of water generates a pressure on the meter of about 0.4 barg. Pump is not running and it is full of water.

Maybe you remember P= height(meters) x Rho (density of water= 1000 kg/m3) x C ( a constant of 9.81) / 100000 (to get from N/m2 to Bar).

The meter doesnt show, so pipe is empty or meter is not working. You took of the protection of the thread or inlet of meter or is there any other blockage? Or meter has a major offset due to falling or bumping it to hard. In the back there could be a zero adjustment screw, as i see it is not on the pointer. Otherwise meter is broken.

Probably you also over estimate the pressure by pump?

The pump brings it up from 3 meters down the well and then up to a tank 4 meters, so thats a loss of 7 meters.

You have a pump curve, is that given in meters or does it maybe say feet? 40 meter is 4 barg tops with almost no flow, but 40 feet = 12 meters= 1.2 barg, then going up 7 meters, so leaving 1,2 - 0.7= 0,4 barg, when running, and should be showing on meter, when that one works. This is only going straight up, however you also have losses due to used pipe material, bends, valves, filters, viscosity, temperature and so on. 

 

IF you only use the pump for filling your tank, you dont need a pressure switch to control on/off. The level switch would be the only one for controlling. You use a pressure switch if it is also used with a water system with valves in it, opening and closing. A valve closes, pressure goes up and switch off the pump.

In case of ONLY filling up tank, you need only level.

Unless you like to protect tank and you have a pressure switch to switch of the pump, in case the level meter wouldnt switch off. However again if tank is not closed and is open to environment, it is useless. It will just overflow then.

There is a water tap. To turn the pump on when the tap is turned on I needed a pressure switch. So the pump turns on when the tap turns on or when the float switch activates.

2 reasons for the tap. 1. If I didn't have one my wife  would want one.

2. To monitor the quality of water at the pump source. 

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13 hours ago, Yellowtail said:

That would depend on how much higher the open end of the pipe is than the gage, yes? 

Correct, it would only read the head difference between the gauge and the outlet

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