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Old 01-27-2012, 08:55 AM   #1
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On-demand water heater


Hello,
I'd like to install an on demand water heater, but I'm not sure my well will deliver the needed flow for the unit to operate. The one I'm considering requires water pressure of 22 psi-which I have-and a flow rate of .93 gpm. According to my measurments, I'm getting about .75 gpm. Can I install a booster pump to increase the flow?

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Old 01-27-2012, 10:04 AM   #2
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On-demand water heater


Pressure of 22 psi would be exceptionally low for a well system, mine is pretty typical and operates between 40 and 65 psi. As to the flow rate, you are probably reading the maximum delivered hot water capacity of the unit at 0.93 gpm. The unit does not include a pump, so it will heat whatever flow you deliver to it UP TO 0.93 gpm. If your well only pumps 0.75 gpm (which sounds very low), then your heater will heat 0.75 gpm. However, these numbers seem pretty odd.

Consider that the average low flow shower delivers 1.5 gpm, and if you happen to be showering while running the dishwasher or clothes washer, you will need to deliver at least 2.5 gpm, which your pump should easily be able to accommodate. You may be looking at the long term allowable flow rate for your pump, which could be quite low, for example the allowable long term flow rate for my well is only 0.75 gpm, but there is a lot of storage in my well, so it is not a problem when demand is high (could be up to 6 - 8 gpm when there are numerous fixtures running simultaneously). I suspect your situation is similar, in that the pump itself can deliver more instantaneous flow than the long term capacity of your well, it simply draws the water down temporarily during high demand periods.

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Old 01-27-2012, 10:15 AM   #3
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On-demand water heater


Hi Daniel,
My system is operating at 35 psi; what I meant to say was it meets the minimum 22 psi required by the heater. As for the .75 gpm, I measured this at the kitchen faucet with a gallon milk jug and a stopwatch. Not very scientific, I know, and after I read your post I realized that perhaps the faucet has a water saving feature. However, I do notice that, for example, while the toilet is refilling, water flow at any faucet is reduced. So would it matter if I installed the booster, or would this just be spitting into the wind? Thanks.
Ben
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