If I want the well pump to start less frequently, why should NOT the pressure of the bladder tank be GREATER than the well pressure start setting. I have a 30-50 well pump pressure switch which kicks in at what looks like 32 psi according to the in-line pressure gauge next to it. I have 28 psi in the bladder tank as most recommend, which results in the well pressure switch starting the pump every time the psi drops a few pounds, which seems like less than 1/2 gallon of water flow. If I had for example, 35 psi in the bladder tank, would that not lessen the frequency that the well pump is activated?

  • If the switch is a 30-50 nominal and is cutting in at 32, it should be cutting out at about 52, so it should be considerably more than "drops a few pounds" to start the pump - 20PSI differential, so it should have to drop 20 pounds before it starts again. Are there other details you might need to edit in that you have not mentioned? – Ecnerwal May 8 at 16:41
  • To really make the pump cycle less often increase the spread on pressure switch on off. most folks want a uniform pressure is why the narrow spread between the set points. On one home I had really long line it really pulled the line voltage down so we set the cut in at 40 and the cut out at 100 this way the pump was starting less often and was less prone to overheating even when watering the yard. We did put a pressure regulator at the house set at 40 so we only saw a tiny fluctuation, we had tried a higher set point but in the summer the well could produce enough for a constant 45psi. – Ed Beal May 8 at 17:07
  • Thanks guys about raising the cut out setting; makes such sense now that you say it – Joe3 May 9 at 17:34

Because the pump does not start instantly. The 2-3 PSI below cut-in is to provide water while the pump is starting - without it, pressure will drop to zero (or very nearly) every time when water runs out but the pump is still spinning up. Indeed, you can evaluate actual adequacy of pressure (in case your tire gauge and water gauge might disagree) by observing behavior as water runs and the pump cycles on - if it does not dip below the tank setting, you can try adding a bit more air, until it does, and then you can let a bit out until it does not. But most gauges are adequately precise that this is rarely needed.

If you want the pump to start less frequently, add more pressure tank volume (either a single larger tank, or additional tanks) and consider running at a lower pressure (look at a tank chart for volume from 20-40 .vs. 30-50 or 40-60 - the tank holds more water at the lower pressure, due to physics.)

Of course, you appear to have 4 psi differential, not 2-3. You may also have a failed bladder/diaphragm if the pump is operating very frequently, but if you are measuring the tank pressure with the water pressure at 0 and a drain valve open, as you should, and it is holding at 28, then you should either add a pound or two, or adjust your pressure switch down a pound or two.

But if everything is otherwise correct and the pump starts after a gallon or two, you probably need more tank volume.

  • Kind of picky, but tank does not hold more water at lower pressure. Less volume of water is push out/over time at lower pressure. – crip659 May 8 at 16:54
  • Wrong, @crip659. The air in the tank is compressed by 1/2 in a 20/40 setting as the water enters. The air in the tank is compressed by 2/5ths at a 30/50 setting. The amount the air is compressed is also the volume of water stored, which is less as the tank pressure increases (since the "standard" differential remains at 20 PSI) - go look at a tank chart. – Ecnerwal May 8 at 17:00
  • It will increase water volume some, but think the amount of water being push out due to the pressure change, might be a bigger factor/over time. 5gals/min compared to 4gals/min. – crip659 May 8 at 17:09
  • The volume gained is not enough to make a difference if the problem is as described anyway, but in actual fact, your first comment is just dead wrong, period. – Ecnerwal May 8 at 17:12

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