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    pisces789's Avatar
    pisces789 Posts: 1, Reputation: 1
    New Member
     
    #1

    Apr 19, 2008, 11:32 PM
    Tankless hot water heater connections.
    I may have made a mistake. I just bought a tankless hot water heater with 1/2 inch water connection fittings. My house used 3/4 inch water pipes. Is it OK to reduce from 3/4 to 1/2 inch copper pipe and connect to the hot water heater and then as the water leaves the heater to go back from 1/2 to 3/4 inch copper pipe? Thanks for any info!
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
    Senior Plumbing Expert
     
    #2

    Apr 20, 2008, 04:52 AM
    Hey Pisces:

    No mistake there... not ideal.. but no mistake. There will be a drop in VOLUME.. but pressure should not decrease... read on.

    Tankless coils at boilers are only 1/2" tappings...and most everyone connects 1/2" pipe to them or JUMP to 3/4" no problem.

    Some tankless water heaters, like yours, actually want to have 1/2" tappings to control the volume of water getting heated at one time (3/4" tapping/feed may overwhelm the system and reduce ability to heat the water as fast as it does).

    Still... I want you to call the manufacturer of your particular tankless water heater and I want you to pose this question to their technical department... just so you can be 100% sure. I don't want you to find out that this is in fact an issue later... say 1/2 way into winter next year (I don't even know what particular tankless hot water heater we are talking about.. so I am just GENERALIZING for you)!

    Call them... let us know what they said... Mark
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber
     
    #3

    Apr 20, 2008, 05:04 AM
    Connecting a fixture with 3/4" inlets with a 1/2" supply? Bad idea!
    Connecting a fixture with 1/2" inlets off a 3/4" main with a 1/2" supply? Good plumbing practice! Another great answer by Mark. Tom

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