We have a deep-well (230 feet) domestic water system. I usually turn off the pump and electric water heater when we'll be away for a while, partly to save electricity and to limit damage in case a pipe bursts. When we returned home after being away for a few days, the whole-house filter filled with sediment, but the system pressurized. I turned it off again and replaced the filter. It promptly filled again. I decided that now was the time to replace the 28-year-old pressure tank and add a sediment filter in the line before the well water gets to the tank. All went well and the system functioned fine until the first drawdown of the tank. When the pressure decreased to the cut-in point for the pressure switch, the pressure dropped to almost nothing and stayed that way for about 30 seconds. Eventually pressure returned and the system pressurized normally. But it keeps doing this every time the pump turns on. I've tried adjusting the pressure on the bladder tank to no avail. Is there a pump problem? I hate the thought of pulling that out of the ground unless I have to.

Putting the filter between the pump and the pressure tank/pressure switch absolutely should NOT be done. If the filter is dirty or plugged you can get VERY high pressures in the line between the pump and the filter element. This could compromise the filter sump causing it to burst. They have some serious warnings on those things about pressure limits. PLEASE put your filter AFTER the pressure tank and pressure switch. There can be no restrictions between the pump and the pressure switch. This could be the cause of the pressure problem you describe. Be glad the filter housing hasn't failed yet.

If you haven't moved the filter, then it is a tank precharge problem or an incorrectly operating pressure switch. Get a good tire pressure gauge and check the pressure in the tank and compare it to the pressure gauge on the manifold. If the manifold gauge isn't correct, do the math and apply the correction to all subsequent readings of the manifold gauge.

Open the drain valve on the manifold a bit and slowly lower the pressure until the pump cuts in. Note that (corrected) pressure. Turn the pump off and drain the tank the rest of the way. Then check the precharge pressure of the tank. It must be about 2 psi lower than the cut-in setting of the pressure switch. Adjust the tank pressure accordingly (it probably is higher than it should be), then restart the pump.

If it isn't the precharge, the pressure switch could be full of dirt or the nipple it is mounted on (if it is steel) could be rusted shut. This also would cause the symptoms you describe. Replace them both, and use a BRASS nipple to mount the new pressure switch. The extra dollar or so that it costs is the cheapest insurance against those problems that you can buy.

The sediment problem sounds like your water table is lower than normal or else there was a bit of a cave-in in the well. It will clear up with time.

Thanks for the response. I understood every word you wrote.

The filter I installed is a Lowe's item with a polycarbonite tank, a screen, and drain cock specifically intended for use before the pressure tank. It's called a tank-saver filter. The whole-house filter is a string-wound cartridge filter between the tank manifold and the house plumbing.

The manifold, pressure switch, and nipple were removed when the new tank was installed, cleaned out and reinstalled. The pressure switch cuts in at 30 psi like it should. That's when the pressure drops. The sediment has been in the well since it was drilled almost 30 years ago. The old tank was full of it, hence the new tank. Air pressure in the tank is 27 psi when the pump circuit is switched off and the tank drained. BTW, the pre-tank filter has not a speck of sediment in it yet.

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Originally Posted by sercanet

<snip>The manifold, pressure switch, and nipple were removed when the new tank was installed, cleaned out and reinstalled. The pressure switch cuts in at 30 psi like it should. That's when the pressure drops. The sediment has been in the well since it was drilled almost 30 years ago. The old tank was full of it, hence the new tank. Air pressure in the tank is 27 psi when the pump circuit is switched off and the tank drained. BTW, the pre-tank filter has not a speck of sediment in it yet.

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I assume that you have a submersible pump. Maybe the check valve in the pump has problems. Or the well pipe has some restriction or leak. Can the pump bring the pressure back up to cut-out pressure in reasonable time or does it take a long time? I am starting to lean toward telling you to get a good plumber in, but finding one with GOOD troubleshooting skills is a must here. I just don't have enough information to go farther and I'm getting too sleepy to figure any more tonight, maybe someone else can chime in.

Yes, it's a submersible, about the only thing you can use at 230 feet down. The pressure comes back up pretty quickly once it reaches 30 psi; there's just that 30 second or so delay when it drops suddenly and has to come back up to 30 psi. It reaches cut-off (50 psi) about a minute later.

Thanks for trying.

I wish I could see that pump output into no restriction. That would tell me some things. I still think it is a tank precharge problem, but I'm at my limit of troubleshooting with the information I have.

Good luck.

EPM