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spencerin
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# Posted: 22 Sep 2026 11:54pm
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The "innernet" seems to say that if your pump is 10 GPM or less, a minimum 1 minute run time is best. Example - a 10 GPM pump corresponds to a 10 gallon drawdown/refill in a minute, which roughly corresponds to a 30 gallon pressure tank.
Does any of you have anything smaller than that, or smaller ratio, and not have any issues? I know having a pressure tank protects the life of the pump, but my space is limited, so I'm looking at something in the 20 gallon range. Seeing as the pump wouldn't be used that often, I'm wondering if I can pair it with a slightly smaller tank without issue for a long time.
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Brettny
Member
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# Posted: 23 Sep 2026 08:27am
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Would two smaller tanks fit the area better? 20gal is better than a 10gal tank.
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spencerin
Member
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# Posted: 23 Sep 2026 08:41am
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I can fit a 20 gal, but 30 is what seems recommended. Curious if the smaller size really wouldn't be that impactful given lighter long-term use.
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Steve_S
Member
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# Posted: 23 Sep 2026 12:10pm - Edited by: Steve_S
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Well, I have a 40 Gallon pressure tank in my pumphouse. I use a Grundfos SQ5 120V Soft-start deep well pump (280' deep). My settings are 40 PSI to start pump and 52 PSI cutoff (full pressure). I forget how much water my well flows but it is within Banded Granite and flows really well, even my well driller was surprised at how well it flowed in.
In over a decade now, I never had any issues whatsoever. Thanks to the staged pump, the pressure drop is not really noticeable (even in the hot shower).
1) The well has to be able to replenish faster than you can use it up with all taps open.
2) Your pump, has to be able to keep that pressure up even when your pressure tank is drained.
3) Pressure Tank Volume is relative and not really that big of a problem unless you have one that is too small which will result in running the pump a lot more. *
* Key reason I went with a bigger tank with my system because the pump does not have to run that often which saves me power... I am offgrid & 100% solar powered, so I am energy conscious on everything. IE my pump starts at 750W and stages up in 250W increments till it cuts off at 52 PSI and 1500W being pulled from the system. Believe it or not, it does not take very long to go from 40 to 52 PSI.
A NOTE which affects pressure a bit. I run with a dual filtering system. The first filter is a large Sediment Filter which is between pump & water pressure tank. The second filter is a fine particle filter at the entry point in my house which then goes to everything else in the house. I lose about 2PSI in total between the pressure tank & house. NB: There is 75' of 3/4" PEX from pressure tank to house distribution point.
Hope it helps, Good Luck.
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branbin
Member
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# Posted: 13 Oct 2026 08:10am
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With light use, you're fine. Pump wear comes mostly from the number of starts, not total gallons, so occasional cabin use means far fewer cycles than a full-time house.
A 20 gallon gives about 5 to 6 gallons of drawdown at 40/60, so roughly a 30 second run with a 10 GPM pump. Not ideal, but workable. Just make sure the precharge is set about 2 PSI below cut-in with the tank empty, and if it ever short cycles, a cycle stop valve is a cheap fix.
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