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Check valve on return side

Baggypolo
Baggypolo Member Posts: 4
So I have a 6 zone water system. I have the Taco Flo-Chek valves on the supply side after each pump. I don't have any check valves on the return side. I noticed the zones that aren't on, their return side pipes are hot. Should I install check valves on the return side as well? If so, should I install similar Taco Flo-Chek valves or regular spring loaded brass check valves? 

Comments

  • Baggypolo
    Baggypolo Member Posts: 4
    Another update, the Taco Flo Chek valves I have on the supply side after the pump for each zone, I noticed one of the zones that is off is hot on the supply side after the Flo-Chek valve... These valves should prevent against gravity flow... Is the valve not working properly? 
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,145
    Flow checks can be on the supply or the return but you only need one on each zone normally. They are only put on the supply & return in extreme situations.

    If you find a pump off and the pipe is hot the pump may have just shut off

    or

    you could have a bad flow check valve


    Even if the flow checks work properly and are on the supply for instance the returns may get a little warm from hot water migrating up the returns but just for a short distance and not very hot
  • Baggypolo
    Baggypolo Member Posts: 4
    edited November 2021
    So this one particular issue I'm having with phantom flow is a lot of water is going up one particular zone and the last radiator in that zone is very hot and the second to last radiator is like warm.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,145
    @Baggypolo

    If you have hot water going up the return and heating the lats two 2 radiators on a zone and you have a flow check on the supply then add a flow check to the return. It has to be in a horizontal level pipe.

    a normal swing check valve should work as well since you have a flow check on the supply
  • Hot_John
    Hot_John Member Posts: 1
    I have a similar issue with a couple of zones using pumps with check valves. I'm wondering if the system circulator has enough head that it pushes water through the zone pump check valves. Can't otherwise explain why my zones are heating with zone pumps not running. A second related question.. Taco flow check valves open when they sense flow, and are otherwise closed. Is their function different than a (horizontal) swing check? I could see a swing check waft open with little flow, and thus not necessarily stop a convection flow. I am wondering if the flow check doesn't have more initial resistance, so that it will only open with the kind of pressure provided by a pump, thus being more effective at stopping ghost heating? Anybody know ?
  • Peakedtoosoon
    Peakedtoosoon Member Posts: 8
    edited May 18
    If you have a seperate supply and return header (not looped), a "spring-loaded" check valve is required on the discharge side of the vertical zone pump (integral or in-line). The in-line check should be located about 10 pipe diameters downstream of the pump discharge. The spring-loaded check valve should open at a pressure differential of 0.2 to 0.3psi, to mitigate against any ghost flow (thermal migration).

    If you have a looped, common supply and return header (sometimes referred to as a series primary/secondary loop), then you need a second check valve on the return to the header, to prevent thermal migration, up through the vertical return leg.

    Thing to remember is hotter (less dense) water will want to rise, in vertical piping, if given a path to do so. A great way to see this in action is with a thermal imaging camera.
  • pedmec
    pedmec Member Posts: 206
    yes there is a difference between a flow check and a swing check. a flow check is a weighted check and needs the forced of the circulator to open. a swing check is just that, a door that just swings open on a pin that acts like a hinge and can be forced open just a little with the warm water trying to migrate up if mounted horizontal (recommended).