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I have changed the pressure gauge, a Square D switch, and checked the pressure (from 40 psi) to 28 psi. Within 3 to 4 days the pressure increased back to 40 psi. I called a plumber who lowered the pressure to 28 psi (as I had done). Again the pressure has risen to 40 psi. I lowered it to 28 psi.

Where and why is the pressure rising? The attending plumber was at a bit of a loss.

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2 Answers

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Per your other thread, it sounds like you're measuring the pressure in the tank's bladder. If this is the case: don't. In fact, if you're releasing pressure to get it to 28, you've actually screwed up the calibration of your tank, your pump is likely going to be cycling faster than it should be, which will wear out the pump faster as well as cause fluctuations in the water pressuring in your house.

The tank pressure is irrelevant while the system is running. The valve at the top of the tank is for setting the pre-charge pressure.

tank pre-charge valve

The pressure you should care about is on the gauge at the base of your tank: this is the water pressuring going to your house.

bottom of tank

To set up the pre-charge correctly for a 40-60 PSI range:

  1. Turn off the power to the pump, then open a tap until all the water drains out (so your system pressure is 0).
  2. Via the valve on top of your tank, set the pre-charge pressure in the tank to whatever the manufacturer recommends: typically 4 PSI below the low pressure limit (so, 36 PSI).

Now you can adjust your pressure switch, if needed:

  1. Turn off the valve to the rest of the house, and turn the pump back on. Your goal is for it to stop at 60 PSI.
  2. If it goes higher/lower, adjust the big nut until it shuts off at 60.
  3. You may have to open the valve to release pressure so the pump kicks in again, and repeat several times.
  4. Now open the valve to the house (run some water). The pump should turn on at 50. If not, adjust the small nut until it does.

Keep in mind to adjust the pressure switch, the big nut (green arrow) adjusts the overall pressure, while the little nut (red arrow) adjusts the range between the on and off values.

enter image description here

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I am hoping the plumber completed the neccessary finer adjustments. In your top picture where you show the "pre-charge valve"... I never touched it. I was adjusting the pressure through the nipple behind it with the large cap. What is it for? – Michael J Dec 4 '12 at 1:08
@MichaelJ honestly, I've never looked (and I worked on water systems for a few years). It still sounds like you've screwed with the precharge, so you should follow my instructions to check and also check the operating pressure (watch the cut-in/out pressures on the gauge). Also, most plumbers know crap-all about water treatment and pressure systems, so don't rely on hope. :) Granted, I may be biased, but I've had to clean up after plumbers "fixed" treatment systems more times than I can count.. – gregmac Dec 4 '12 at 4:39
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Did you run a drill down through the short section of small pipe that the pressure switch attaches to?

These things rust shut due to the small pipe diameter and water acidity/iron bacteria.

I dealt with it by replacing the pipe with brass after the third time it happened. 70psi on the house plumbing was a little scary.

Due to the restriction, the pump and gauge are on a separate hydraulic circuit, you keep lowering the switch pressure to compensate for it so it shuts off at, say 25 psi to maintain the max 40 psi on the other circuit. After the switch shuts off, of course over time, it will see 40psi as well.

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Thank you for your response. – Michael J Dec 2 '12 at 20:02
Fiasco Labs, I am not sure I understand your instructions. When you mention the "short section of small pipe" is that the black abs / pvc (?) pipe which attaches the submersed pump with the D switch / gauge. My D switch / gauge is srewed into a brass T with a water exit tap. – Michael J Dec 2 '12 at 20:15
Most of the switch installations I've been involved with have a combined check-valve body with ports to install a switch on the outflow side of the check-valve or a sort of brass tee affair that connects to the water tank with a port in it for the switch and a port for the gauge. Because it's cheap around here, instead of connecting the pressure valve with a piece of 1/4 brass pipe, they'll use a piece of 1/4" galvanized iron pipe which rusts internally. Anything that causes a restriction between the pressure switch and the water system can cause the symptoms you describe. – Fiasco Labs Dec 2 '12 at 20:29
So, what was the pipe the pressure switch screws on to made of? – Fiasco Labs Dec 2 '12 at 20:31
Most of the pictures fall under copyright, so I can't use them here. deanbennett.com/tank-fittings.htm shows what I'm talking about. The pipe that pressure switch is mounted on. Make sure it's unrestricted. – Fiasco Labs Dec 2 '12 at 20:49
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