I have three homes on my well pump. Each home has its own bladder type well tank. One is a 20 gallon, one is a 24 gallon, and one is a 62 gallon. The well pump cut in/cut out is 30/40. I set the air pressure on all three at the recommended 28 psi.

The 20 and 24 gallon tanks fill up normally, but the 62 gallon only fills to about 10 gallons. I lowered the air pressure to 10 psi in the 62 gallon tank and it fills much fuller now, but I'm not sure if it will work like that. Any words of wisdom will be appreciated.

  • I'm no expert on wells, but for what it's worth: I would look into installing a single larger pressure tank to serve all three households. Having one pressure tank triple the size of the other two seems like, even if you can get it to work, is always going to complicate analysis and diagnosis of problems with the system. Dec 14, 2020 at 1:10
  • @PeterDuniho I don't think that has any bearing on this, and won't be an improvement (pressure tank at each house will make each house work better than a single central tank would.) The "problem" described is not a problem, other than one of not applying/interpolating the specs to the situation. If there is an actual problem, it hasn't been described. If the pump is not at one of the houses, a fourth tank near the pump might make sense - then again, the 62 gallon tank might be at the house with the pump. But we haven't been told any of that information.
    – Ecnerwal
    Dec 14, 2020 at 1:43

1 Answer 1


You have an abnormally small differential (20/40 or 30/50 are more typical, for a 20 PSI differential rather than a 10 psi differential) which will impact storage on all tanks.

Referring to a tank chart for a 62 gallon bladder type tank, the 20/40 drawdown is about 22.6 gallons and the 30/50 drawdown is about 19.2 gallons, so 10 gallons of drawdown at 30/40 seems perfectly normal - i.e. nothing was wrong with that figure for that size tank at that pressure differential.

All that you achieve by lowering the precharge to 10PSI is a big slug of water that sits in the tank and does nothing for you, since the tank still starts refilling at 30 PSI. You may also stress the bladder since you are running a bigger slug of water in the bladder at 40 PSI than you would be with a 28 PSI precharge. You'll still only move 10 gallons of that water each pump cycle, but now you'll have (probably 20+ gallons, starting from 10 PSI and goingup 30 PSI is not a standard tank chart figure) that just stays in the tank all the time - so instead of the bladder going from near empty to just over 10 gallons, it will go from (guesstimated) 20+ to 30+ gallons.

  • Yes,I was wrong it is a 30/50 differential. So shouldn't it be holding approx. 19.2 gallons? Dec 14, 2020 at 23:59

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