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.
On Wed, 17 Nov 2004 14:56:01 GMT, email@example.com (Doug Miller)
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.
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.
On Thu, 18 Nov 2004 01:17:00 GMT, firstname.lastname@example.org (Doug Miller)
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.
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
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
email@example.com (Doug Miller) wrote in message
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.
On 17 Nov 2004 19:40:44 -0800, firstname.lastname@example.org (Harry K)
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.
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.
Fine with me. How much do you want to wager?
There's _no_way_ that the pressure is _ever_ going to go higher than the
cutoff setting on the well control, unless the control malfunctions.
And as soon as the pressure reaches the cutoff setting on the well control,
the pump shuts off, and the pressure goes no higher. If that does _not_
happen, then you need to replace the control unit, because it's
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