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I am new to having a well and the pressure in our house is OK, but not incredible. The well sits about 100 ft. from the house. We have 2 20 Gallon pressure tanks next to the pump. The pressure switch is a 40/60. The pressure reads about 43 psi. I am curious if I can set the pressure higher or if I risk damaging the system. The majority of the plumbing in the house is PEX.

Tank specs: enter image description here

Pressure switch: enter image description here

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You can, but it's not all to the good...

Normally, most household plumbing fixtures (especially toilet valves) prefer a pressure of no more than 80 PSI. Your pipes are nearly always not the limiting factor. Most well pump controllers have a fixed 20PSI swing from on to off, but many can be adjusted so they can swing 40-60, 50-70, 60-80, 30-50, 23.5-43.5 etc.

The volume of water stored in your pressure tanks becomes less as the pressure is raised - a captive air tank swinging from 40 to 20 PSI stores far more water than one swinging from 80 to 60 PSI. This matters because more pump starts is one of the factors that leads eventually to pump death and replacement, always a fun time. So if you raise the system pressure, you should probably also increase your storage tank volume to prevent having lots of very short pump cycles. Switching over to a "constant pressure" (or "nearly constant pressure") system is another alternative, though it can be costly.

If you change system pressure, you need to change precharge air pressure in captive air tanks (typically about 2-3 PSI less than the lower cut-in pressure - ie, 58 lb for an 80-60 setting.)

You should observe system pressure as water is used - a properly functioning 40-60 PSI system should drop to about 40, switch on the pump and raise to 60, switch off the pump and drop to 40 as water is used. When no water is used the system pressure should hold steady. If you turn off all other water use and measure exactly how much water is needed to drop from 60 to 40 you can gauge the health and current storage capacity of your pressure tanks. If you measure the time it takes to refill from 40-60 (without drawing any more water) you will know your pumping rate (and if it takes less than a minute, conventional wisdom is that you already need more storage capacity.)

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  • I was thinking somewhere between 55 / 75. About 10 more PSI than I have now. Do you think that is possible for my current setup? Since i Have 2 tanks would I set them each to 53 PSI or are they balanced at 26.5 / 26.5 psi
    – DDiVita
    Oct 20 '15 at 18:53
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    @DDiVita They operate in parallel, so 53 PSI for both (set with the water pressure at 0 - pump off, system drained.)
    – Ecnerwal
    Oct 20 '15 at 19:02
  • Do you mean if it takes more than a minute? Then need more storage...
    – Matt
    Mar 27 '18 at 18:32
  • No - if it takes less than a minute of pumping to fill your pressure tank(s) they are not storing enough water, and your pump is starting too often as a result.
    – Ecnerwal
    Aug 16 at 18:43
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It is important to know where the pressure SWITCH is, as that is what is controlling your pressure.

You didn't say where your pressure switch is or what the elevation of the house and switch is. I'm assuming (usually a bad thing) that the switch is near the tanks based on the picture, but the house could be higher than the switch.

Water pressure changes by 0.433 psi per foot of elevation, so if your switch is 20 feet lower than the house, then at the low end of the 40 - 60 range (40) you will only have 40 - (20 * .433) = 31.34 psi at the house instead of the 40 psi you are expecting.

Let the system build up pressure and then measure the static water pressure (no water being used and pump off) at the switch or well (hopefully you have a spigot there) and at the house. Check for any differential and factor that into your pressure calculation when adjusting your pressure.

You said the well and tanks are about 100 feet from the house so you can also have a pressure drop due to the distance of piping and size of pipe used - only when the water is being used, statically you will not see this. Using 2" pipe * 100 feet @ 18 GPM = about a .3 psi drop.

So for this reason, you typically want the tanks and the pressure switch to be near the house NOT the well (my well is 150 feet LOWER than my house). If the switch and the house are about level and they used 2" pipes, then it probably doesn't matter much if the tanks are at the well or the house.

Otherwise, what Ecnerwal said.

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(Yes, I know this question is old...but I'm answering for the next person who comes along with the same question)

OK, lets start by actually answering your question :-). The correct answer is yes, you can change the cut-on/cut-off setting without damaging your system as long as you stay within a reasonable range. That said, here are things to consider.

First though, I need to correct an answer that was given above. The volume of water in your pressure tanks WILL NOT change based on pressure! Volume is volume. It would require extraordinarily high pressure to compress water sufficiently to impact volume capacity of a rigid container.

So, on to real considerations:

  1. Higher pressure puts more stress on plumbing. You said you have PEX, which means your plumbing is newer (good thing). As long as you are not above 80, you are at "safe" levels. I personally prefer to stay well below that threshold (no more than 70)

  2. Be sure your well pump can reach the cut-off pressure you set -- otherwise it will keep running until it burns up.

  3. Pressure is only one side of the coin. Flow is the other. Raising the pressure will push water out of the tanks faster, but once the capacity of the tanks is exhausted you are going to be at whatever pressure/flow your well produces. This will be more noticeable at higher difference between the two. As example, if you set your tanks at 70psi cut-off (which will normally be 50psi cut-on), but your well pump only produces 30psi steady pressure at its flow rate, you are going to get a strong surge for a few minutes, then a rather sudden drop-off. But if you were to set your pressure switch to 30/50, you will have less of a surge and more of a "steady flow". This is all personal preference, nothing to do with safety of your system.

IMPORTANT -- if you decide to change the cut-on/cut-off on your well, be sure to also adjust the pressure tank. It should be charged to 2psi lower than your cut-off (e.g. 40psi cut-off means pressure tank should be set at 38psi). The tank needs to be basically empty when checking or adjusting charge pressure, otherwise you will not have an accurate reading for the charge.

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  • Such a clueless "correction" - pressure tanks have water and air in the them. The air is what is compressed. Compressing air from 20 to 40 PSI results in about half the tank volume being water that can be used. Compressing it from 60-80 PSI results in about 1/4 the tank volume being water that can be used. That's what pressure tanks DO...
    – Ecnerwal
    Aug 16 at 18:38
  • i.e. see the charts here: diy.stackexchange.com/a/62696/18078
    – Ecnerwal
    Aug 17 at 13:19
  • You need to learn about fluid dynamics and how pressure of water relates to pressure of air within a closed system. Sorry, but if you get some education you will realize my correction was far from "clueless".
    – diybob
    Aug 19 at 19:53
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This will depend on the well pump's ability to output pressure but my thoughts would be to boost up the on pressure to the minimum you're willing to have in the house and the off pressure to a much higher value to get more storage out of your tanks. Then use a pressure reducing valve for the water going to the house to dial it back down to the minimum pressure you want in the pipes. That way you have no risk of damage to whatever is in the house and won't have varying pressure based on usage and you'll help extend life of the pump from less pump cycles. If possible, go get a larger expansion tank so you can store more water at a time too.

I have city water pressure that is pretty consistently 100 psi at my home. and at my business we have a really large well system that's on at 38 psi and off at 70 psi. We set the off to 70 psi due to paranoia of the pipes blowing, which had been an issue in the past but I think due to a pump that was too powerful for the demand. That pump has since been replaced from burning out so I've been thinking about changing it to on at 50 and maybe off at around 100 or potentially higher, then just use pressure reducing valves to maintain 50 psi to the building. PVC is rated for 150 psi working pressure so all should be ok as long as I can verify the limitations of the well pump's pressure output.

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