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Zonevalves Feed or Return, Pros and Cons

NYplumber Member Posts: 503
Good evening wallies,

First post on the updated forum. The process seems fluid. Thank you @DanHolohan‌!

Onto the topic at hand, pros and cons for zone valves on the feed, and pros and cons for the return side.

Off the top of the hat:
Feed side
- Pros: prevents heat migration
- - Cons: banging, low cv zv's will cause a slight drop in pressure possibly allowing an air pocket up in the loop (injection effect)
Return side
- Pros: away from the hottest water, less banging from a valve closing, pump pushes full pressure through the pipe (less air bubbles form)
-Cons: Heat migration up the supply pipes when other zones call

What are your thoughts?


  • Jamie Hall
    Jamie Hall Member Posts: 19,147
    Mostly thinking from the point of view of the hydraulics, having almost no actual experience with hot water heat!

    If you are pumping away and the valve is downstream from the pump, the slight pressure drop though a zone valve shouldn't be a problem. Banging (which shouldn't happen at all) shouldn't be a problem either way, as the velocity through the valve will be the same in either case.

    Hopefully someone who really knows will chime in here...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 16,547
    maybe your actual piping method determines the best location. Either will get the job done. If the zone takeoffs are vertical from the boiler supply header, supply side give you that 100% shutoff for unwanted flow in the "off" zones.

    If the piping goes down or horizontal from the boiler header, return works well.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • icesailor
    icesailor Member Posts: 7,265
    I didn't know there was a contrary word until I came here. I've seen them on the supply and return. I never noticed any difference. I used ZV's that were positive shut-off's. So I always put them on the supply and a BV and drain on the return. All within easy reach for easy purging. Everything I did revolved around easy purging.
  • Rich_49
    Rich_49 Member Posts: 2,693
    Variable speed pumps will take away the banging . Properly set up piping and air elimination using quality equipment takes care of air . Supply side stops unwanted flow , return side will be cooler so it probably isn't gonna rise into the zone . Don't use low Cv zone valves . Get and keep all the air out that is possible .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • NYplumber
    NYplumber Member Posts: 503
    Thanks for the answers ya'all. Personally we never experienced banging or air, just searching for the best way. As expected both work quiet well.