Hot water line size

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by keydash, Jul 15, 2010.

  1. keydash

    keydash New Member

    Messages:
    15
    Location:
    Oklahoma
    Uncertain about what size of hot water line to use.

    Small structure: 1 shower, lav, toilet, washer, kit sink.

    The cold water line is 3/4 pex reducing to 1/2 at the bibs, then to 3/8 at fixtures other than the washer. I will be using an on demand water heater connected to the pex through a length of iron pipe.

    Question: Should I follow the same sizing for the hot water line as laid out for the cold water line or just run 1/2 pex for the hot throughout? The water heater has a 3/4 inlet and outlet.
  2. nhmaster3015

    nhmaster3015 Master Plumber

    Messages:
    836
    Location:
    The granite state
    follow the manufacturers directions. On demand heaters are sensitive to flow
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Conventional wisdom says 3/4 copper ( 1" PEX) for the mains, reducing to 1/2" copper ( 3/4" PEX) for individual fixtures. These days, for low flow fixtures like lav faucets and showers, the smaller pipes have advantages. But for hi-demand fixtures like a tub or washing machine, you would quickly regret smaller pipes.
  4. Gary Slusser

    Gary Slusser That's all folks!

    I'd get rid of that piece of iron/steel pipe and since all tank less water heaters are flow controlled (already), I'd not run less than 3/4" to it. Steel/iron pipe rusts adding iron to the water and hard water voids the warranty on the tank less heaters.
Similar Threads: water line
Forum Title Date
Plumbing Forum, Professional & DIY Advice Water line foundation penetration call-back. Sunday at 4:22 PM
Plumbing Forum, Professional & DIY Advice Removing the water supply line on a kitchen sink Nov 16, 2014
Plumbing Forum, Professional & DIY Advice How to tell if I have a hot water return line Nov 7, 2014
Plumbing Forum, Professional & DIY Advice work with 1" water heating main line Oct 7, 2014
Plumbing Forum, Professional & DIY Advice Fridge Water Line Problem Aug 1, 2014

Share This Page