Water pump on/off every 3 seconds

[Doug Miller]

When you do, precharge the tank to 2 psi below the cut-ON setting on the control. Trust me. That's how it's supposed to work.

[Doug Miller]

You're getting different readings because you're using different gauges. One or both is not accurate. Which one is "right" doesn't really matter.

The only thing that matters is the reading on the gauge at the well control. If the pump comes on when *that* gauge reads 42 PSI, then you need to precharge the tank with air to a reading of 40 PSI on *that* gauge. Forget about the readings at the top of the tank. They are *not* relevant.

If the bladder is broken, it unquestionably is *not* holding the air pressure, any more than a broken balloon can hold air pressure. A pressure tank does not need a bladder at all in order to function; however, without a bladder, the air will eventually be absorbed by the water, a little at a time, until there's almost no air left -- which is exactly the problem that prompted your original post. The purpose of a bladder is to prevent this absorption.

Normally, yes. In your case, though, the bladder has apparently ruptured.

AFAIK, that diaphragm is pretty near the bottom of the tank, so the air space below it is so small as to be irrelevant.

[Doug Miller]

Disagree. A large tank can also be indicative of a homeowner who likes to have a really high pressure and flow rate in his shower, without short-cycling his pump by a small draw-down. :-) At our previous place, we had a high-output submersible pump (it would fill a 200-gallon livestock tank in about 10-12 minutes), and an 85-gallon pressure tank, with pressures set at 50/90.

[Jud McCranie]

IIRC, after I drained the water, that gauge showed 0 PSI after I drained the tank and still showed 0 after I pumped up the tank, which seems to make sense if the diaphragm is not completely broken, but only has a small leak.

[Doug Miller]

No, it doesn't. Even in a tank with no diaphragm at all, the gauge should read whatever pressure the tank has been precharged to, provided that: a) the gauge is operating properly b) there is no blockage in the tube leading to the gauge c) all the valves are closed d) there are no leaks in the system.

[Harry K]

Well yes but only after the pre-charge has been set. At least in my tank and it sounds like in Jud's too the pressure gauge on the well-trol reads 0 even with the correct precharge when the tank is empty. I can only assume that the bag blocks the tank outlet. Thus a tire gauge is needed to set the pre-charge. You are correct tho that after the pre-charge is set, ignore what the tire valve reading says.

Harry K

[Jud McCranie]

I checked it, and the water pressure gauge does go to 0 when I drain the tank - even though the air bladder is still pressurized. I just don't see how that gauge could be affected by the air pressure inside the bladder, because that gauge is outside the bladder. With the bladder/diaphragm between them, there is no contact between the air in the bladder and the gauge in the water line. It is sort of like if you measure the air pressure in one tire, it doesn't affect the pressure in another tire.

[Jud McCranie]

That's what I think, but isn't the bag supposed to be airtight? (It holds the pressure.)

Here's my setup. There is a pipe coming from the well, there is a T off of that. There is a T off of one of those branches, and one leg of that T goes to the pressure switch and the other goes to the water pressure gauge. Back to the other leg of the T off the main line, one leg goes into the house and the other goes into the bottom of the tank. From what I understand, there is a diaphragm in the tank that makes an air bladder at the top. On the top of the tank is a valve similar to a tire gauge except that it is metal. I stick my air pressure gauges to that, and use it to pump up the air.

When I drain the tank I cut off the pump and open a couple of faucets. The water pressure gauge goes down to zero. The air pressure drops down, but it holds at about 20 PSI (checked with 2 gauges). It holds that way. Then I close the faucets. If I pump air into the top of the tank, the pressure goes up there, but it has no effect on the pressure at the water gauge. I think the diaphragm is keeping the air in the bladder at the top of the tank, but I thought that is what it is supposed to do.

[Doug Miller]

It's *supposed* to be, yes. Yours *isn't*. That's how your tank got waterlogged.

[Harry K]

Yes, your understanding is correct. Actually the bag does not hold the air, it holds the water (the water is pumped into the bag or it is in mine anyhow). The bag's only purpose is to separate the air from the water. Without it (or a 'snifter valve') the air is absorbed into the water shortly resulting in a waterlogged tank. That is why you have your problem - the bag is broken allowing the air bubble to gradually disappear. The reason you get a zero reading on the tank gauge when you drain it is that the bag is blocking the tank inlet/outlet. Thus that guage will read zero while the air valve on top will show whatever pre-charge you have.

Use the gauge on top to establish the pre-charge with the tank empty. Again that is 2 psi approx under the cut-in pressure. Once you have that set correctly, use the tank gauge to monitor the system.

Harry K

[Chris Lewis]

According to Jud McCranie :

This is suggestive that the bladder _is_ working properly.

When you relieve all the pressure off the water line, the diaphragm "settles" down around the inlet and acts as a pressure dam.

But once the water starts to become pressurized and comes in contact with the diaphragm and "lifts it off" the bottom, basic physics says that the water and air pressure will be identical (within a PSI or so). If they're not, your pressure gauges are simply not being consistent.