Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Recirc Pump to Cold line with RO system

martinamw Member Posts: 1
Hello, I've bought the pump already and only thought about possible contamination afterwards. Not yet installed, it's the type that uses the cold water line and mixing valve, instead of dedicated return line.

I'm wondering are any tricks, using check valves, to attempt at keeping the RO line clean / cold water only. Or should I just return this, and to it using a dedicated line.

Thanks in advance.

Rough pipe distance: RO System <> 20 feet <> Water Tank <> 20 feet Bathroom


  • HomerJSmith
    HomerJSmith Member Posts: 1,370
    martinamw, good question. No one want warm water coming out of their RO faucet.

    Best bet a dedicated return line. I guess you are doing this to improve the water taste and getting rid of the trihalomethanes along with chlorine.
  • hot_rod
    hot_rod Member Posts: 15,037
    Just my personal opinion, but RO is overkill for treating drinking water, it strips all the good parts out of the water with the bad.
    A selection of cartridge filters can "polish" water to remove taste and odor. The key is identifying what you want removed.
    Knowing the RO water needs to be in plastic as it eats through metallic piping is enough reason for me to not drink it :)

    I suspect RO membranes have a temperature limitation?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream