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New Watts 70 tempering valve hot on both sides

Hi all - Just had a plumber replace the Watts 70A valve on my tankless boiler. Finally, I have great hot water throughout house again. I used to have a well, but am now on town water, which is great quality. My question is, If I dont use any hot water at all, the outlet pipe for the hot water is hot for several feet. This may be non issue, as everything is working great. I guess I thought unless the hot water is on, the valve completely closes. If it doesn't, or not supposed to, then I can easily see why the outlet pipe would be hot for a few feet. I have outlet pipe insulated also. The cold line going in is cold. The hot pipe from inside furnace is hot as hell, and the outlet is hot for maybe 5 feet. I am just checking to see if its normal, as the valve was replaced a month ago and complete assembly was replaced, piped in exactly as the 20yo one came out. I never felt the hot water outlet line on older valve, so I dont know if this is ok. Thoughts other than junk it? Thanks!!!


  • GroundUp
    GroundUp Member Posts: 1,957
    Just conduction, nothing to worry about. Odd that a 70 is doing what it's supposed to, they never do that lol
  • Havoc2000
    Havoc2000 Member Posts: 2
    HAHA Thank you for your reply! The old one was broken in half when taken out. A month prior to installing new mixer I switched to town water, which is very clean here, and not hard like my well was. If it's just conduction, then I'm happy it's doing its job right, and isnt subjected to hard water.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,171
    edited May 2021
    GroundUp said:

    Just conduction, nothing to worry about. Odd that a 70 is doing what it's supposed to, they never do that lol

    Ground-up... Give it a few weeks, Havoc2000 will be back to ask more questions.

    JUST KIDDING. The 70A is old school and does not meet the code requirements for ASSE 1017 or ASSE 1070. Not a big thing, but the 70A can fail in an unsafe condition by design. (meaning the water can come ut too hot). The Watts LFMMVM1 does meet those standards (which means it will fail cold) for just a small increase in cost. The piping arrangements are slightly different and that may be the reason your plumber choose to use the Watts 70A.

    My company policy is to always upgrade to the better product for the job, In this case, it would have chosen the Honeywell AM100 series. Just my personal choice.

    Respectfully submitted

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Ctoilman
    Ctoilman Member Posts: 105
    I second that about the Honeywell AM100 mixer, rather than the Watts 70A.  Nothing terribly wrong with the Watts, just keep a spare element on hand ($25/Ebay) and change it out when the element corroded (5 yrs).  I've only changed 2 Honeywell elements in like 10 yrs now for comparison.