Well design.. OK you professional plumbers

7 year old well/home. original pump I believe is a 3/4 hp. It's still functional and don't have paper work so I'm not sure. I can tell you 1-1/4" line feeding the house. I have a 20 gal well-x-trol pressure tank. well is 220 ft deep. I have a call into the well company to get the Draw down on the well. The 20 gal pressure tank was definately a cost savings for the contractor but is definately undersized from what I can tell. Below 1 hp I should have had a 44 gal pressure tank.(Until I hear from the well company, I may have 1 hp). Now that you have the background: Noticed after 7 years that the pressure doesn't seem as good as it should. Cut in is 25 and cut out is 45. Always been there and maybe we're just starting to notice, with all the yard work. X-trol says tank pressure should be 1-2 lbs below cut in. I'm about 7 lbs below cut in. At very least I know I need to get that back in specs. Would like to turn pressure up a bit. Say up to 50-60 lbs cut out. I know I'd have to adjust bladder pressure up also.Would I be looking for trouble turning pressure up 10-15lbs after 7 years? If I wanted to increase pressure, turn well pump breaker off first, drain tank, then pressurize to 1-2 lbs less than cut in? Procedure? Major concern is I don't want to induce a pump or pressure tank failure. Pump at 3/4 horse should have a 1-1/2 minute cycle time..(it is much shorter now). Would I be doing the pump and/or tank good or would I be hurting them by increasing pressure at this time? thanks, Bill
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Beeper wrote:

That's an undersized tank for almost any well...20 gal isn't much reserve even for just household use.

I'd not increase the shutoff pressure. This doesn't quite make sense to me...a shorter pump cycle time implies a leaking diaphragm/bladder, but that would raise air pressure as some water will displace air space. Of course, you could also have a small air leak in the valve.
Drain the tank entirely and see if there's any indication of water left (by weight, sound, temperature). Depending on whether it's bladder or diaphragm the orientation is somewhat variable.
The empty tank pressure should be 2 lb below the setpoint. Cycling the pump frequently is indication normally of the loss of volume owing to bladder failure.
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Beeper wrote:

There should be no problem in raising the pressure as long as the pump is rated for it and it almost assuredly is.
Yes, drain tank, decide what pressure you want the cut-in and pressure to 2psi below that. Maintain the 20psi differential between cut-in cut-out. There are controllers available that provide a constant pressure but I haven't used nor worked on them.
Common settings are (but you don't have to stick to them) 20-30 - IMO too low but would be useable for house use only. Poor shower performance. 30-50 - about minimum if you are irrigating IMO. That is what I have 40-60 - Max recommended for residential. Higher pressures cause wear/tear on fixtures.
The pre-charge is only there to provide a bubble of air to be compressed. It has no effect on delivered water pressure. The 2psi below cut-in optimizes the pump run time for whatever pressure setting you are using. It results in the minimum start/stop cycles. The starting is what causes most wear on a pump.
Of course there if the pump/well is much lower/higher than the house you have to make allowances for that. .43 psi per foot difference. No change in pressure settings if the tank is in the house.
Harry K
Harry K
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Harry, Great info!! Got all the figures from the well company. Well is 220 ft deep. Only 1/2 HP motor rated at 7 gpm. well is rated at 25 gpm. draw down is approx. 20 ft . according to well x-trol site the 20 gal tank is what it calls for. I'm surprised. Although with a 25 gpm well , I would think a higher flow pump would of been in order. anyway, the spec sheet for the pump on the goulds site wants to know the "feet to water". I'm not sure what they are looking for. Depth to the top of the water? Depth of well? depth from pump to top of water after draw down? Would you happen to know? I guess from what I'm seeing, this helps determine your cut in and cut out PSI.. I'd like to take your advice and up my cutin out to 30-50. Wanna be sure pump is ok with that.

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Some people do a secondary unit. Pump pushes up to a nonpressurized reservior, then another pump delivers from that to a pressure bladder unit. That's essentially what happens with a cistern, too. I know of one that has a 500 gallon tank in their basement, and they have a really small pump delivering from their well into a 1/2" line so that it is less likely to cause cycling problems to the well. The tank has a float microswitch that calls for water when it has dropped a hundred gallons. They say they have all the water they want. BTW, they also routed outside spigots and toilet flushing water so they are not chlorinated.

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The "feet to water" is the vertical distance from the gauge (pressure tank) to water level in well (typically while pumping). You have not mentioned how far down it is from ground surface to water surface, which may be close enough, but can vary over time (dry years or over pumping). If you have a pump curve, it will show X gpm @ Y feet of head. To figure out X you need to know Y. Ignoring piping head loss for now:
Y = (psi_gauge_press * 2.31) + vertical_ft_from_gauge2pumping_H2O_level
When my sister's family built their house which had roughly a 200' well, they used a 1 hp pump and 82 gal pressure tank (set 40-60 psi). You could flush a toilet without kicking on the pump. You could open all 3 spigots outside full blast and the pump maintained 45 psi.

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