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In my neighborhood we have a well-based system which pumps water to holding tanks a little uphill from my house. The vertical drop isn't very much so the incoming pressure is low ~10psi. We have an Amtrol RP-10HP followed by a 5 micron 4.5" x 20" filter then a Aqua-Pure System AP904. The pressure to the house is low even with new filters and the pump causes cavitation when running. I need to come up with a system that provides better constant pressure and good filtration. Here is what I'm thinking:

supply ->
pump ->
filters (maybe with a ~15 micron, 5 micron, then carbon filter) ->
Amtrol WX-350 119 gallon pressure tank ->
Amtrol RP-10HP presurizer

It seems like this could work but there is a risk we drain the 119 gallon tank faster than it can refill, which would causes issues. Would this work to solve our pressure issues? Is there a better setup?

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  • Cavitation may indicate your getting feed volume issues not just low pressure, check the filter? And use low flow nozzles, showers…
    – mark f
    Jul 17, 2022 at 16:17
  • You can not make water out of nothing. There was a guy who turned water into wine, but that is another story.
    – Traveler
    Jul 17, 2022 at 18:23
  • Your 119 gallon holding tank is a joke. You need 3-5 times as much, assuming the well will support it and fill it up in 24 hours. If not, you need better well or more powerful well pump. typical American household uses over 300 gallons of water per day. After solving this problem you can think of your filtration system.
    – Traveler
    Jul 17, 2022 at 18:38

2 Answers 2

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Three little words: add a cistern.

Your biggest problem is that your community water supply can’t supply water as fast as you can use it. You can continue adding pressure tanks and try to mitigate the cavitation in the booster with flow control as another answer suggests. But a better long term solution is to bury a roto molded cistern somewhere on your property. How big? As big as you can afford. Probably no less than 500 gallons.

Although cisterns aren’t cheap, it would be a one-time investment that may be cheaper in the long run than adding multiple pressure tanks and replacing pumps that wear out from cavitation.

Supply the cistern through a float-actuated valve connected to your water supply so that it will self-fill as needed using community water pressure. Install a cistern pump in the cistern. This is a submersible pump that looks just like a deep well pump. At that point, your cistern pump will provide all the pressure you need at whatever flow you wish, and your booster pump will never turn on.

If you believe in redundancy, you can set up valves and switches to bypass the cistern and return to your present setup temporarily in the event that your cistern pump fails or you take the cistern out of service for cleaning.

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The Amtrol RP-10HP requires a minimum water main size of 3/4”, a minimum incoming water main flow of 10 GPM and a minimum incoming water pressure of 10 PSI during that 10 GPM flow rate. (See the installation manual.) If your static water pressure is only 10 PSI, your mains pressure at 10 GPM is certainly not 10 PSI, so the Amtrol RP-10HP is not recommend; cavitation will occur, leading to damage and premature failure. A smaller or less powerful booster pump may give longer life.

It may be possible to install a throttling valve after the pump but before the tank to reduce the flow to a point where cavitation will not occur. Some experimentation may be required to find a throttle setting that will restrict flow enough to stop cavitation, but not trigger the pressure switch to shut off the pump. Throttling will not affect the ultimate pressure in your tank, but it will reduce the speed at which the tank refills.

Regarding the question of using water at a rate faster than the pump can replenish the tank, if 119 gallons is not enough, install a second tank, or a third, or as many as it takes not to run out of water.

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