Is my bladder tank bad?

[Steve Brown]

My submersible well pump was short cycling, turning on at 48 psi and off at 63 psi, a range of 15 psi. I'm trying to lower and widen the range so that the pump turns on at 35 psi and off at 55 psi. The pressure switch is a Square D 40/60 model. I turned the power to the pump off, opened the valve to the outside faucet, and let the water pressure fall to zero. Then I adjusted the air pressure in the tank to 33 psi, and it holds that pressure. Adjusting both the center range nut and the side cut-off nut, the best I can get it to do is to turn off at 55 psi, but when the water pressure gets to 45 psi, the flow rate drops to practically nothing and then the pressure drops to 20 psi before the switch turns the pump on again. I would like the water flow to continue until the pressure gets to 35 psi, at which point the pump should turn on again. What would cause the flow to stop at 45 psi?

 

[Reach4]

With the pump off, but the water pressure holding above 40, such as at 45, measure the air pressure. It should be just a little less than the water pressure gauge reading at that point. If there is much difference, try a different air pressure gauge. Your local tire shop can tell you which one is right. If the other air pressure gauge agrees, get a new water pressure gauge.

You may need a new pressure switch too.

 

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[Steve Brown]

With the pump off, but the water pressure holding above 40, such as at 45, measure the air pressure. It should be just a little less than the water pressure gauge reading at that point. If there is much difference, try a different air pressure gauge. Your local tire shop can tell you which one is right. If the other air pressure gauge agrees, get a new water pressure gauge.

You may need a new pressure switch too.

When I add air to the tank, the final reading of the air pressure gauge on the compressor agrees with the tire pressure gauge that I use to check it. The water pressure gauge seems to be working ok; it doesn't get stuck anywhere in the range from zero to 60 psi. With the pump not running, all faucets turned off, and the water pressure holding steady at 48 psi, the air pressure reads 35 psi.

 

[Steve Brown]

With the pump not running, all faucets turned off, and the water pressure holding steady at 48 psi, the air pressure reads 35 psi. The pressure switch was replaced a few years ago.

 

[ACWxRADR]

Steve,

I don't believe that your bladder tank is the culprit here. If, with no water in the system, the bladder tank holds the
33 psi that you filled it with, then I would think it to be ok.

I might be suspicious of the actual pressure switch itself - or the pressure pickup tube that senses the water pressure and transmits it to the pressure switch. Sounds to me as if the real pressure is not being sensed or the switch is not activating when the cut-in pressure reaches the set point.

RADAR

 

[ACWxRADR]

When I add air to the tank, the final reading of the air pressure gauge on the compressor agrees with the tire pressure gauge that I use to check it. The water pressure gauge seems to be working ok; it doesn't get stuck anywhere in the range from zero to 60 psi. With the pump not running, all faucets turned off, and the water pressure holding steady at 48 psi, the air pressure reads 35 psi.

Steve,

You posted while I was writing and I didn't notice.

Since the pressure reading in the air bladder is 35 psi with the water pressure reading at 48 psi, there is a problem here.
The air pressure in the bladder should be very close to the actual water pressure as Reach mentioned. There is something blocked here. Either your water pressure gauge is reading HIGH or the fill port / pipe to the bladder tank is obstructed so bad that it isn't allowing water to enter so the pressure in the bladder tank is actually LOW.

 

[ACWxRADR]

If the pressure in the bladder tank is reading 35 psi, that means that the tank is empty of pressurized water. This explains why there is no water flow as you have no reserve of water in the tank, it is now used up, but the pump has not kicked ON yet, so even the pump is not providing any source of water.

If the WATER pressure gauge is still reading 45, that has to be wrong. In reality it must be much less than that (it is near zero) if you have no water output. Therefore, the port where you are reading the water pressure at is holding higher pressure for some reason and that is preventing your switch from kicking ON.

 

[Steve Brown]

It does seem strange that the air pressure in the tank would be 35 while the water pressure is 48. As I understand it, the bladder holds the water and the tank holds the air. So, higher water pressure in the bladder while the air pressure in the tank is lower suggests to me that the bladder has stretched to its elastic limit and cannot expand any more to bring the air pressure up to the water pressure. I would expect that to happen if there was not enough air in the tank. Maybe I should add air to the tank to bring the air pressure up to the same as the water pressure when it is at 48 psi? Then when water is released from the bladder by turning on a faucet, the air pressure in the tank should come down as the bladder contracts.

 

[Reach4]

Either the water pressure gauge is bad or the nipple leading to the pressure gauge is blocked. The nipple might be shared with the pressure switch, so that could lead to funny pressure switch action too.

As Radar pointed out, symptoms do not point to the pressure tank.

 

[ACWxRADR]

It does seem strange that the air pressure in the tank would be 35 while the water pressure is 48. As I understand it, the bladder holds the water and the tank holds the air. So, higher water pressure in the bladder while the air pressure in the tank is lower suggests to me that the bladder has stretched to its elastic limit and cannot expand any more to bring the air pressure up to the water pressure. I would expect that to happen if there was not enough air in the tank. Maybe I should add air to the tank to bring the air pressure up to the same as the water pressure when it is at 48 psi? Then when water is released from the bladder by turning on a faucet, the air pressure in the tank should come down as the bladder contracts.

Steve,

I believe that you are looking at the pressure tank operation incorrectly.

The bladder contains the air, from the top of the tank. The bladder expands downward to "PUSH" the water out of the open end of the tank at the bottom. When all the water has been expelled from the tank, the bladder is fully expanded and there is no water inside the tank to "PUSH" back against the bladder. At this point, the precharge psi is limited to the air pressure you fill the bladder with. So, in your case 33 to 35 psi. The bladder is fully stretched out at this point.

When you turn your pump on, the water starts to fill the pressure tank and compresses the air bladder within the tank. As the bladder compresses, the air pressure inside it has to increase because your pressure switch doesn't shut the pump OFF until the water pressure that the switch senses reaches 50, 55 or 60 psi, wherever you have the pressure switch cut out point set at.

Therefore, the air pressure in the bladder rises from its minimum psi of 33-35 up to the 50, 55 or 60 psi where the pressure switch shuts the pump off.

If you precharge the bladder to a pressure higher than the cut-in pressure of the switch, you will confuse the switch. The pump will then turn on only when you have reached a much lower volume of water in the tank. This reduces your reserve of water available in the tank before the pump turns on. If you go too high, the pump may not turn back on before you run out of reserve water because the switch may sense the precharge air pressure in the tank as the actual water pressure.

 

[ACWxRADR]

Steve,

I would drain your water system down to zero pressure and then take the fittings associated with your pressure gauge and switch off and clean them all out as best you can. You probably have some iron or calcium scaling or some other blockage in there. Could be "slime" build up from iron or sulfur consuming bacteria. There are many possibilities for a blockage.

Your WATER pressure gauge is reading a higher pressure than actually exists and your pressure switch seems to be reacting as though it is detecting the same false high water pressure, so there is something fouling the same common area of the plumbing where both the pressure gauge and pressure switch pick-up are attached. There is a pocket that is holding unnatural pressure and the pressure in this location takes some time to bleed down to the point where the pressure switch can turn the pump on. By this time, you have exhausted your water reserve in the pressure tank so you run short of water flow.

RADAR

 

[ACWxRADR]

Either the water pressure gauge is bad or the nipple leading to the pressure gauge is blocked. The nipple might be shared with the pressure switch, so that could lead to funny pressure switch action too.

As Radar pointed out, symptoms do not point to the pressure tank.

Reach,

Your analysis is exactly what I believe, too.

 

[Steve Brown]

I posted an update but realized I need to read the above replies first....

 

[Steve Brown]

Then the people at APS Water don't know what they're talking about, because they say the bladder holds the water and the tank holds the air:
http://www.apswater.com/article.asp?id=215&&title=How a bladder pressure tank works&title=How a bladder pressure tank works

Adding air seemed to help, as now the water pressure doesn't drop down to 20 psi before the switch turns the pump no. With the water pressure at 40 psi, I adjusted the air pressure to 38 psi. I set the pressure switch to turn on at 40 psi and off at 60 psi. With a faucet open, the water pressure gradually decreases from 60 psi until it reaches 50 psi, then the water pressure suddenly drops to 40 psi and the pressure switch turns the pump on. What could cause that sudden drop? I figure the bladder or tank becomes empty of water at 50 psi, so the pressure suddenly drops to 40. Now I'm trying to figure out why.

 

[Reach4]

Then the people at APS Water don't know what they're talking about, because they say the bladder holds the water and the tank holds the air:

In the world of bladder tanks, there are both kinds.

But the better captive air pressure tanks today have a diaphragm rather than a bladder. Many people use bladder tank as a generic term, even if the actual tank has a diaphragm rather than a bladder. Some real bladder tanks have replaceable bladders, which are neither cheap nor easy to swap usually. But the life of the bladder is normally much less than the life of a diaphragm. If you posted the make and model (and maybe just the make) we would know what kind you have. The kind that you have is not important to this case. You diaphragm or bladder has not failed. I expect you might still want to know what you have.

 

[Steve Brown]

In the world of bladder tanks, there are both kinds.

But the better captive air pressure tanks today have a diaphragm rather than a bladder. Many people use bladder tank as a generic term, even if the actual tank has a diaphragm rather than a bladder. Some real bladder tanks have replaceable bladders, which are neither cheap nor easy to swap usually. But the life of the bladder is normally much less than the life of a diaphragm. If you posted the make and model (and maybe just the make) we would know what kind you have. The kind that you have is not important to this case. You diaphragm or bladder has not failed. I expect you might still want to know what you have.

The brand name on the tank is PROFLO.

 

[ACWxRADR]

Then the people at APS Water don't know what they're talking about, because they say the bladder holds the water and the tank holds the air:
http://www.apswater.com/article.asp?id=215&&title=How a bladder pressure tank works&title=How a bladder pressure tank works

Steve,

Please do not take the wording posted on the APS web page literally. They are correct, but they applied very poor wording in their description. Their wording is misleading. Study the pictorial diagram of the pressure tank, the first diagram on that page. It is correct.

RADAR

 

[Reach4]

The brand name on the tank is PROFLO.

On http://www.proflo.com/proflo/showRecordList.do?N=4294934696 I clicked a couple, and they both said "Butyl/EPDM diaphragm". So I expect that would apply to their whole line.

 

[Steve Brown]

ok, but as Reach4 wrote, it doesn't really matter, as long as water is on one side of the diaphram and air is on the other. I'm still trying to figure out what could cause the tank to become empty of water at 50 psi, causing the water pressure suddenly to drop to 40 and turn the pressure switch on. One possibility is a flaky pressure gauge and that the system is operating normally. I believe I can verify that without replacing the pressure gauge if I connect another pressure gauge to the garden hose fitting on the manifold that holds the pressure gauge and the switch.

 

[Reach4]

I'm still trying to figure out what could cause the tank to become empty of water at 50 psi, causing the water pressure suddenly to drop to 40 and turn the pressure switch on.

We don't believe your water pressure gauge. Could be a bad gauge, clogged nipple, or both.