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Thread: Low Pressure mystery

  1. #1
    DIY Junior Member dpw-ct's Avatar
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    Default Low Pressure mystery

    I have just installed a new bathroom and am disappointed by the low pressure in the stall shower. Wondering what might be wrong. There does not appear to be any clog or low flow device in the shower head.

    -- I have a private well with pressure tank
    -- Shower is approx 28 vertical feet from the well tank in my basement.
    -- Pex home run to manifold 1/2 inch to bathroom
    -- Mixing valve is Rohl HY19BO
    -- 1/2 copper from mixing valve to shower head and hand shower (have a shut off for each - and we have low pressure even when just one is in use)

  2. #2
    DIYer, not in the trades LLigetfa's Avatar
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    You don't say what pressure you have at the tank but you will lose 12 PSI over that height alone plus whatever losses through line resistance. Add to that, modern showers are mandated by legislation to be low flow.

    You might consider raising the pressure at the tank.

  3. #3
    DIY Junior Member dpw-ct's Avatar
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    Thanks for the quick reply. The switch is 30/50 I checked the pressure gauge on the well tank it is reading 50 psi. Do you think I need to raise the pressure or could there be another explanation. If I should raise it can you tell me how to go about that.

    Thanks



    Quote Originally Posted by LLigetfa View Post
    You don't say what pressure you have at the tank but you will lose 12 PSI over that height alone plus whatever losses through line resistance. Add to that, modern showers are mandated by legislation to be low flow.

    You might consider raising the pressure at the tank.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    There are two adjustment screws on most well pressure switches....one adjusts the max and the other adjusts the spread...or, you could swap the pressure switch for say a 60/40 that is already adjusted.

    Today's valves and showerheads tend to be lower flow than the older ones. 1/2" pex is closer to 3/8" copper, but still should provide more volume than needed for ONE showerhead.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Junior Member dpw-ct's Avatar
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    would I need to adjust the air on the tank as well?

  6. #6
    Moderator & Master Plumber hj's Avatar
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    "low pressure" is a subjective evaluation. Use a gauge to get the "real" and exact pressure, then we can tell you what, if anything, to do.
    Licensed residential and commercial plumber

  7. #7
    DIY Junior Member dpw-ct's Avatar
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    Thanks will do - any heads up on what pressure reading would be good?

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Most valves are designed to work with a minimum of 30-40# or so (some lower). Now, that doesn't mean you'll love their operation at that pressure, but that they'll work. Most people are satisfied with 40-50#. Codes require it to be limited to 80psi - higher and it could just shoot a glass out of your hand when filling it at the sink!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    Moderator & Master Plumber hj's Avatar
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    The pressure should be close to what it is coming into the house. IF both are almost equal and BOTH are low, then you have an external problem, especially if it starts high and then drops to low.
    Licensed residential and commercial plumber

  10. #10
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by dpw-ct View Post
    -- Shower is approx 28 vertical feet from the well tank in my basement.
    Quote Originally Posted by hj View Post
    The pressure should be close to what it is coming into the house...
    Are you forgetting to account for the 28 feet of rise at .43 PSI per foot?

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