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Balancing Valves for DHW Recirculation

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RPK
RPK Member Posts: 109

I'm trying to assist in selecting balance valves for a DHW recirculation application and am running into some anecdotal "evidence" that the chlorine dioxide treatment utilized at the location in question may be shortening the life of the EPDM seals in typical balancing valves. Doing a little internet research suggests that "peroxide cured EPDM" may be more resistant to this chemical than (possibly more commonly available) "sulfur cured". My B&G submittal says their seal material is EPDM (no mention of how it may have been cured). I did find "peroxide cured EPDM" in some submittals for Caleffi balancing valves. Looking at some seal material chemical compatibility charts— it looks like viton is good for the chemical resistance, but apparently not to be utilized in potable water applications… Does anyone have any thoughts on/or experience with this?

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,092
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    This sounds like a @hot_rod question

    Edward Young Retired

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

    RPKTeemok
  • Big Ed_4
    Big Ed_4 Member Posts: 2,806
    edited May 16
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    I am not sure the reason you will need a balance valve is needed . I know a good check valve is needed to direct water flow and prevent bypass …

    There was an error rendering this rich post.

  • Teemok
    Teemok Member, Email Confirmation Posts: 511
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    Is this a constant flow recirc? Single residence or large building. Flow erosion from restricting over pumping might look like chemical deterioration. Could be both. What I mean is, confirm the system makes good sense before worrying about the type of EPDM. DHW recirculation is frequently done poorly and materials get the blame.

  • RPK
    RPK Member Posts: 109
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    This is a very large system. Balancing valves are needed to make sure we get even flow in each of the branches.

    Teemok, this is a large building. It will have a variable speed recirc pump that modulates to maintain return water temp. In systems where you see flow erosion — what is the root cause? Oversized pump, bad piping design?

  • Teemok
    Teemok Member, Email Confirmation Posts: 511
    edited May 15
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    Without specific damage it's impossible for me to say what your situation is. I have seen pipe erosion from high velocity flow and valve erosion from having a larger constant speed pump pushing high head at nearly closed valves. The velocity of flow through the closed down valve is very high and turbulent. That doesn't sound like your situation. I sounds like you are designing to avoid problems now. I'll let hot_rod do his thing,`he knows better than I. Caleffi makes good valves for what you are doing. Where are the failed o rings located in the typical balancing valves? Hot water and oxides are hard on plastics, limited service life. All brass or stainless maybe but it sounds like it's a engineered system so changes should to be well thought out.

  • Doug_7
    Doug_7 Member Posts: 247
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    We use CircuitSolvers by Therm-Omega-Tech to balance our DHW Recirculation flows. This is an in-line wax-capsule type thermal regulating valve that automatically regulates the DHW recirculation flows, to maintain the required temperature. One CircuitSolver is installed on each branch of our DHW Recirculation system.

    Over-pumping the DHW Recirculation is a common problem. Too high a water velocity, over 2 feet / second, causes erosion-corrosion of copper leading to pin-hole leaks, or will cause PEX to split. CircuitSolvers provide the minimum flow required to maintain the recirculation temperature, with no high water velocities. CircuitSolvers are the silver-bullet that solves these problems.

    All metal - No EPDM involved.

    TeemokRPK
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,335
    edited May 16
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    Hi, Erosion at two FPS surprised me. I looked it up and found that is possible at temperatures over 140F. Are you running that hot? Otherwise you should be able to run at five FPS with "hot" water.
    Yours, Larry

  • RPK
    RPK Member Posts: 109
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    In this particular case it will stored at 140F and mixed down to 120F for distribution.

  • Doug_7
    Doug_7 Member Posts: 247
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    There is no erosion of copper in DHW recirculation systems at 2 feet / second velocity. That is the point.

    You need to keep water velocities below 2 feet / second in DHW recirculation systems to prevent erosion-corrosion of copper or splitting of PEX. That is because DHW recirculation is a continuous-flow 24/7/365.

    You can get away with 5 feet / second with normal "hot" water piping - because the flow is so intermittent. But 5 feet / second is far too high for DHW recirculation systems - because the flow is continuous. Big difference.

    Attached is the Manufacturers Recommendation for using PEX in DHW Recirculation systems. Same 2 feet / second maximum velocity recommendation as for copper. Good to follow Manufacturers Recommendations.

  • Doug_7
    Doug_7 Member Posts: 247
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    RPK - Send an e-mail to gambas@shaw.ca and I will send you a Design Guide for DHW Recirculation Systems. Doug

  • hot_rod
    hot_rod Member Posts: 22,256
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    another option is the Caleffi Thermosetter

    This valve is adjustable and has a temperature gauge to dial in temperature you want.

    It’s a temperature solution for a temperature problem

    Always ream the ends of copper tube to prevent turbulence that can cause erosion pinholes

    Peroxide curing the EPDM crosslinks it and makes it more stable for chlorine and chloramine

    With pex recirc piping it is three variables , velocity, temperature, and chlorine levels

    The chlorine rating stamped in the pex is your guide


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream