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Hotwater Install

hr Member Posts: 6,106
required, also. By federal law a shower head should not exceed 2.5 gpm. Typically with 45psi and under 100 feet of piping 1/2" would be fine.

The body spray manufactures bend the rules a bit by limiting the heads to 2.5 but installing 8 of them! Sort of fits the law, but not really the intent of water conservation.

The Vanguard Manablock system uses 3/8 or 1/2 to most fixtures and they have a handy sizing guide for fixture units and available pressure.

The PHCC has a nice sizing wheel for this.

hot rod

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  • Brian C_2
    Brian C_2 Member Posts: 1
    hotwater heater

    i am have a discussion with a friend about installing a hotwater heater. should he pipe the hotwater supply in 1/2 inch pex instead of 3/4 the hotwater heater is about 60 ft away i just thought 1/2 inch would deliver less water and therefore faster time at getting hotwater to the tap
    vs a longer Wait with 3/4 inch is this true

    also will pex pipe stay hotter longer then copper? i told him to insulate no mater what he use's

    thank you
  • Brad White_144
    Brad White_144 Member Posts: 17
    General Rules

    It all depends on the available water pressure, Brian. I will assume for discussion that 3/4" works now at least for the entire water service load.

    The distribution piping has to be sized staring with the available residual pressure and allowing for pipe, fittings and change in elevation to your furthest fixture. My house has higher pressure so works well on 1/2" all the way. Your pressure may be less so figure accordingly. Your local plumbing code may dictate minimum pipe size and flow rates to each fixture also, FWIW.

    You are correct on speed of water delivery increasing with smaller pipe. You will find that with 3/4" to the fixtures, the hot water will take perceptably longer to get there than with 1/2" pipe.

    The size of the CW to the heater matters less, so I would make that 3/4", but the delivery HW piping to the fixtures I would make smaller if the available pressure supports it.

    Depending on your local plumbing code, and at least here in MA if you are over 100 feet of developed pipe length away from the heating source, you have to install a recirculation system (or- gad!- electric heating cable) to minimize prolonged cold draws. I think recirculation is a good idea and economical at far lesser distances too.

    Regardless, you should insulate the piping, but especially if use with recirculation. Yes, copper conducts better than PEX, but PEX also conducts well (it is used in radiant floors after all).
  • Brian C_3
    Brian C_3 Member Posts: 1

    thank you guys this is a good website loaded with info

    so would it be more efficient that he pipe his hotwater main in pex because copper cools down faster then pex. pex will keep the water hotter in the pipe for longer do i have this right?

  • Brad White_144
    Brad White_144 Member Posts: 17
    Pex and Heat Retention

    The ability of PEX to transmit heat is less than copper, sure, but not enough to make a difference in my decision to insulate it. I would insulate each with enthusiasm (and Armaflex. Not sure if enthusiasm alone has appreciable R-value.)

    If copper cools to ambient in five minutes, PEX might be what now, eight minutes? Just a guess. Not enough to get excited over, in my opinion. And not enough to allow you to use "Navy Shower" techniques.

    Nothing wrong with the appropriate PEX so long as it is Code-Compliant for your area. My decision would be based on the economics, all other things being equal.
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