Potable water accumulator pressure.

[Stephen Wade]

We have a private water supply from a borehole. The water from the borehole goes to a treatment plant that includes an accumulator vessel. I would like to know what the pressure should be set to in this vessel, as the pump has started switching on an off frequently so I believe the vessel needs recharging. In the past this has been done by our water plant maintainer, but it looks straightforward to just use a compressor to do this, in fact I have connected my compressor and put some air in, but I don't know what the safe working pressure is. It is a red Italian made vertical vessel.

 

[Valveman]

The air charge in the tank should be 2-5 PSI less than the start pressure of the pump. 40/60 switch, needs 35-38 PSI air in the tank. You can only check the air in the tank with a tire gauge and only after shutting off the pump and draining the tank of water. The water pressure gauge needs to read zero while the tire gauge on the tank determines how much air should be in the tank. And if the tank is low on air, the bladder in the tank is probably torn from cycling on and off too much.

 

[RS]

Is a borehole a well? Is an accumulator vessel a pressure tank, and does it have a bladder, with a schrader valve on top? If so, verify what the pressure is when the pump starts,then shut off the power to the pump, bleed off all the water pressure, and air up the tank (through the schrader valve) to 2 psi less than the cut in pressure. Most pressure switches are set to 40-60 psi, so the tanks are pre-charged to 38. If you end up with the water flow stopping altogether before the pump starts then you have pre-charged it a little too much, lower the pre-charge until it works properly. You can pre-charge a tank without a bladder too, but you will have to drain all the water and put the air in through the drain valve.

 

[Stephen Wade]

Thanks for your replies, that helps me to understand what is going on a bit better! Yes the borehole is a well. Yes my pressure vessel/accumulator has a schrader valve on top. Now I understand that I can't add air unless the pump is off, and I drain the accumulator. I suspect there may be a problem with the bladder/diaphragm as the pump is cycling on/off every minute or so even with no water usage. I will see what the pressure is like after I have switched the pump off and drained it.

 

[Stephen Wade]

Tried to add a couple of pictures in last post.

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• Stephen Wade
• Feb 3, 2020

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• Stephen Wade
• Feb 3, 2020

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• Stephen Wade
• Feb 3, 2020

 

[Stephen Wade]

I've been watching the pump cycling, and it is dropping to 40 then switching on, but it only gets to 50psi before switching off again. It takes a minute or so to repeat this cycle. There are no taps open or water being used in washing machine etc, so I don't know why the pressure is dropping. Any ideas what I should be looking for? I've just been round the house making sure there are no running taps or leaks.....

 

[RS]

Now that you mention that the pump starts/stops even when no water is being used, that changes everything, the pressure tank is possibly working correctly! You have a water leak, either in the house or in the well. It looks like you have valve between the pressure tank and a softener, (the big blue tank) you can shut that off to isolate the problem. If the pump still cycles on/off then you have leak between the pump and the tank, and could be a check valve, leaking water back into the well. I assume you have a submersible pump down in the well? Most submersible pumps come with a check valve in the top. If they're not too deep it's possible to pull them by hand, but there are many ways to set them up depending on if you live in a climate where freezing is a problem.

 

[RS]

I forgot to mention, the short term solution is to shut off the power to the pump when you don't need water, having the pump start/stop every minute when your not using water is severely shortening it's life!

 

[Stephen Wade]

I forgot to mention, the short term solution is to shut off the power to the pump when you don't need water, having the pump start/stop every minute when your not using water is severely shortening it's life!

HI Russ, I did what you suggested and closed the valve to the filter tank. The pump stopped cycling. As you said, this meant a water usage somewhere in the house system. I found a valve in the house that had been left open in error by our plumber when fixing a leak recently (he had drained the system to replace a section of 28mm copper pipe) As soon as I closed this valve again, the pump cycling stopped, and we still have full water pressure in the house. I don't know where the water was going from the open valve, I certainly couldn't see any leaks or overflows, but anyway it appears to be fixed. Many thanks for your advice. Cheers, Steve.

 

[RS]

Very glad I was able to help you! We had the same situation once, but it was a broken fitting on the outside of the well casing, 7 feet down! I dug down with a shovel and found it and fixed it !