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flow checks

STEVEN MARKS Member Posts: 154
Do most installers replace the flow checks for residential boiler replacements?
Is it common practice to move existing pumps on a multizone system during a boiler replacement from the return to the supply for the benefit of pumping away from the expansion tank?
Single zone systems I find it easy to this. It is common practice for me.
Multi-zone systems I find it harder to this (competetive price) with the additional increase of labor and material.
Any Thoughts?


  • Brad White_2
    Brad White_2 Member Posts: 188
    What I have seen done

    and have myself recommended on competitive projects is to move the expansion tank connection point to just upstream of the circulators rather than move all of the circulators downstream of the expansion tank. That is the key feature you want of course, to pump away.

    Why move X number of devices (and wiring) when you can move a single 1/2" pipe?

    The only thing you give up is that your air separator might not be at the lowest pressure in the system anymore, but is that such a big deal? I think not. A good Spirovent or Taco Pall Ring separator and you are in business; even if you do nothing, you can still get the air out soon enough.
    STEVEN MARKS Member Posts: 154

    Thanks Brad
    On a 3 zone system with circulators on the boiler return. Would you install the expansion tank downstream of one of the circulators?
    What about the flow checks?
  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    What I do is.....

    I install a single pump on the supply for all the zones and install zone valves on the return.....and balance valves as necessary. Most of my systems are full reset, so running a single larger pump for all zones is much more energy efficient than three, often the same size pumps for each zone. Installing the pressure tank on the zone return befor the pump causes the pump to increase the pressure in the boiler in many setups...possibly casung the relief valve to blow off.

    I usually use the old flowcehecks on systems as long as they are the old fashioned weighted brass units... these are very reliable and I still use them new instead of flow check pumps or flanges when I want to make sure problems will not occur.


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  • Brad White_2
    Brad White_2 Member Posts: 188
    Boilerpro hit it far more accurately

    I wrote before thinking it through better. The situations I had were "zone valve on supply" scenarios with a single circulator on the return (duh on my part) and the others were single-zone circulators on return, so the fix was quick.

    With multiple circulators, you do not have a lot of choices short of installing a number of smaller expansion tanks, one upstream of each. -I will have to think more about that one!

    The expansion tank only goes downstream of any circulator if you want a problem there.
    STEVEN MARKS Member Posts: 154

    I like the idea of a single pump on the supply and replacing the the pumps on the return with zone valves. In the future I will try to sell the jobs this way. The existing boiler that I have to replace the customer wanted to reuse the existing pumps since they are relatively new. I take pride in my work and like to do things right when I can but sometimes it doesn't pay. The consensus from some of the people I work with and some of my competition is it's worked the last 50 years this way why change. Dont reinvent the wheel
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