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Thread: Increasing System Pressure

  1. #1

    Default Increasing System Pressure

    I have a tankless hot water system that requires a min flow rate of 2 gallons per minute. My water is supplied by a 1/2 hp Gould submerssible which currently feeds into a 17 year old Well-X-Trol 20 gallon pressure tank with pressure settings set at 30 to 50 psi. The tank is pretty well saturated so I have a new X-Trol 205 (34 gallon) pressure tank that I'm getting ready to install. Right now, the hot water runs hot while the pressure is up but fades to cold when the pressure drops before the pump cycles.
    My question is: When I go in to replace the pressure tank, would there be any harm installing a 40-60 pressure switch and replacing the 30-50? The new tank is already set at 38 psi and the system is all sweated copper with no pvc so I'm not worried about pressure leaks. Would the extra 10 psi create any serious strain on the pump? Could there be any other problems or risks? Any advice would be welcome. Thanks.

  2. #2
    In the Trades Bob NH's Avatar
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    Oct 2005
    New Hampshire


    You don't say what model pump but most of them will develop a lot of pressure as flow is reduced. I suspect that the only effect will be reduced flow from the pump in the 50 to 60 psi range.

    You will probably get reduced cycling with the higher pressure (that is good) as flow rate is reduced.

  3. #3


    Well, increase the pressure for sure, but I have doubts about the 2gpm minimum flow. I have used many of these with radiant systems and the figure of .25 gpm comes to mind. [I am discussing gas or propane units] You can watch the burners modulate gas pressure as the flow decreases to nearly zero... 10+ years ago I might believe you on that figure.

    One could not wash his hands with warm water if they designed to 2 gpm. Perhaps you need a new heater or have a problem in the gas modulation.

    Some tankless heaters have tiny and nearly invisible slotted head flow control valves at the inlet or outlet, and you might investigate that. You may also increase the outlet water temperature that will reduce high limit shut offs.

    Also you can do 45 - 65 pressure and put a pressure regulator before the hot water set at 45 or so. But I would have a close look at the heater first.
    Last edited by Raucina; 04-15-2007 at 12:02 AM.


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