Pressure tank overcharging

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Pipewrenched

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Hi all. I have a few year old WellXTroll WX250 and a 40/60 switch. My submersible pump was short cycling so I did some simple tests of shutting the pump off, draining the tank and checking the pressure. It was at 60+. And when I drained the tank, it took about 30 seconds, so there's no way it was "full". I let air out until it was about 38psi. Everything seemed good and it no longer short cycled. But after a day it starts doing it again. So I rinse and repeat, same results. Tank over charges again after some use. We did recently have my pump replaced (two weeks ago) and we had alot of sediment when everything got stirred up. Could this be a clogged pressure switch or is there air getting in the tank somehow or something else building pressure?

Thx
 

LLigetfa

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If the precharge goes up it is due to a leaking diaphragm. Often the leak is one way so it jacks up the precharge and won't bleed back down on its own.
 

LLigetfa

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Correct. Some folks incorrectly call it a bladder.

well-x-trol-wx-202-pressurized-well-tank.jpg
 

Pipewrenched

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Correct. Some folks incorrectly call it a bladder.

well-x-trol-wx-202-pressurized-well-tank.jpg
Gotcha.

How does that introduce air into the tank, or am I not understanding?

I just lowered the air again now. When I turn the well back on it fills up and hits the cutoff almost within 30 seconds, it can't possibly fill up that quick? When I tap on the tank it sounds normal, hollow at the top and solid near the bottom.
 

Pipewrenched

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Interesting. Does the water get stuck on the air side then? When I drain the water from the tank to reset the pressure, almost nothing comes out. I've let air out at least 10 times now and then it starts short cycling the pump shortly after use. I drain the water and the empty tank pressure is back up to 50-60 again.

At this point it's over my head so I've called a local plumber to try and get him out tomorrow to check it. Just trying to grasp any info myself so I can learn.
 

LLigetfa

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Does the water get stuck on the air side then? . . . I've let air out at least 10 times now...
Yes, that is a classic failure. The weight of the water presses the rubber against the bottom port, not letting it out Try lifting the tank to get a feel of how heavy it is with the water trapped above the diaphragm.

If you bled off air ten times, there should not be any air left. Do you at any time get air sputtering out the faucets? If the tank is not heavy from being waterlogged, there is a possibility extra air is being introduced by the pump AND you have a leak in the diaphragm where the surplus air crosses over. Again one-way, the same as with waterlogging.

How the pump could make air is if you have a top-side check valve AND a leak between it and the pump OR a failed check valve in the pump. Every time the pump shuts off, the water column drops by gravity and sucks air in through the leak in the pipe. On the next pump start, the air in the pipe gets pushed to the tank ahead of the column of water. Usually, this would produce so much air that it will spit out of faucets but you've not mentioned that symptom.
 

Pipewrenched

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Yes, that is a classic failure. The weight of the water presses the rubber against the bottom port, not letting it out Try lifting the tank to get a feel of how heavy it is with the water trapped above the diaphragm.

If you bled off air ten times, there should not be any air left. Do you at any time get air sputtering out the faucets? If the tank is not heavy from being waterlogged, there is a possibility extra air is being introduced by the pump AND you have a leak in the diaphragm where the surplus air crosses over. Again one-way, the same as with waterlogging.

How the pump could make air is if you have a top-side check valve AND a leak between it and the pump OR a failed check valve in the pump. Every time the pump shuts off, the water column drops by gravity and sucks air in through the leak in the pipe. On the next pump start, the air in the pipe gets pushed to the tank ahead of the column of water. Usually, this would produce so much air that it will spit out of faucets but you've not mentioned that symptom.
Thanks, great explanation. I have not noticed any air coming out of faucets. Our well is 600' and we just had it all pulled out to replace the wiring that was rubbed through. Figured might as well replace the pump while it's out. That was about 3 weeks ago. Very plausible one of the check valves maybe went as well. Plumber will be here at 8am tomorrow to check everything.

The only other thing I've noticed happening for well over a year now was a "lull" in tap pressure every so often. It seemed to happen for a split second right when the pump would kick on.
 

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Thanks, great explanation. I have not noticed any air coming out of faucets. Our well is 600' and we just had it all pulled out to replace the wiring that was rubbed through. Figured might as well replace the pump while it's out. That was about 3 weeks ago. Very plausible one of the check valves maybe went as well. Plumber will be here at 8am tomorrow to check everything.

The only other thing I've noticed happening for well over a year now was a "lull" in tap pressure every so often. It seemed to happen for a split second right when the pump would kick on.
As was said, the diaphragm in the tank is torn. Water is getting trapped on the air side, which increase pressure and causes the lull in water when the pump starts. Every problem you mentioned is caused by the pump cycling on and off too much. The tank diaphragm failure, the chaffed wire, and the bad check valve, where all caused by the pump cycling on and off too much. The pump itself was most likely on its last leg as well.

Replacing the tank is easy, but why not solve all those problems while you are at it? Adding a Cycle Stop Valve does just that, delivers strong constant pressure to the showers, and makes the pump, tank, and everything else last longer. And since the Cycle Stop Valve is what stops the cycling, you can use as small as a 4.5 gallon size tank as a replacement for that huge one. Everything you need including the 4.5 gallon tank is in the PK1A kit.

 

Pipewrenched

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As was said, the diaphragm in the tank is torn. Water is getting trapped on the air side, which increase pressure and causes the lull in water when the pump starts. Every problem you mentioned is caused by the pump cycling on and off too much. The tank diaphragm failure, the chaffed wire, and the bad check valve, where all caused by the pump cycling on and off too much. The pump itself was most likely on its last leg as well.

Replacing the tank is easy, but why not solve all those problems while you are at it? Adding a Cycle Stop Valve does just that, delivers strong constant pressure to the showers, and makes the pump, tank, and everything else last longer. And since the Cycle Stop Valve is what stops the cycling, you can use as small as a 4.5 gallon size tank as a replacement for that huge one. Everything you need including the 4.5 gallon tank is in the PK1A kit.


@Valveman I like this... makes sense. Does this require a special variable speed pump ?
 

Bannerman

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Very plausible one of the check valves maybe went as well.
You said 'one of the check valves'. There should only be one check valve, and that should be located at the bottom of the well where the submersible pump is located. If there are multiple check valves in your system, that will usually cause problems even if your pump installer says otherwise.


Does this require a special variable speed pump
A CSV does not require a variable speed pump. It will work with the pump you already own.
 

Valveman

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@Valveman I like this... makes sense. Does this require a special variable speed pump ?
Lol! No. But every pump manufacturer and many pump installers will try to make you think only a variable speed pump could do that. Most don't want you to know a simple Cycle Stop Valve will do a better job than any variable speed pump. The main reason they don't like CSV's is because they will make the pump and system last several times longer than a variable speed pump and cost a fraction of the price.
 

Pipewrenched

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Maybe I misspoke, is a check valve the same as backflow valve? I have one of those right before the pressure switch and one about half way down in the well line.

I inquired about the CSV but it won't work with my system due to the high backpressure, calculated to be around 248psi. My well line won't handle it, as it is of the black plastic type.

Plumber was here this am, replaced the tank/switch and all is well (for now, at least!).
 

Valveman

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Maybe I misspoke, is a check valve the same as backflow valve? I have one of those right before the pressure switch and one about half way down in the well line.

I inquired about the CSV but it won't work with my system due to the high backpressure, calculated to be around 248psi. My well line won't handle it, as it is of the black plastic type.

Plumber was here this am, replaced the tank/switch and all is well (for now, at least!).
Back pressure from a pump capable of 600' depth is a problem if the static level is shallow like 50'-100'. But when you have to replace that pump check the static water level on the pipe you pull out and check the pump curves before replacing the pump. Most likely you can get a pump that will deliver from that depth and still not have excessive back pressure. Some applications like that it is just impossible to use a CSV, but you are missing out on lots of benefits. If you can install a pump with less back pressure in the future the CSV will still be here to help. I may not be as I have put in way more than 50 years so far. But there is a new generation coming up that will be glad to help. Thanks
 
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