one zone does not shut off

[williamliew]

my plumber added one zone into my hot water baseboard heating system (with one more returning pipe curculator), but the third zone does not shut off (circulator is off but the third zone is still hot) when the second zone is on. I suspect the third zone requires the pipe to go below the circulator and go up to give some negative pressure to the thrid zone circulator (that is, stop the thrid zone circulation when the third zone circulator is not running). Am I right? If yes, I would ask the plumber to run the pipe again to solve the problem.

[NJ Trooper]

I don't think re-piping is necessary.

Probably what you are experiencing is 'ghost flow' ...

When one circulator runs, it causes flow in the other zone. In order to stop that flow a 'check valve' may be required.

What is the model of circulators that you have?

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[williamliew]

NJ Trooper, thank you so much.

I certainly need two more flow check valves as the second and the third zones share the same outgoing pipe (out of the furnace) which splits at one of the bedroom doors (I know it is not a good design but is much cheaper to use the existing pipe loops). I either need to install the two flow check valves at the bedroom door (that looks funny and is costly), or I may install them somewhere close to the returning circulators. My questions are (1) can I install the two flow check valves around the returning circulators? (2) if yes, should I install the flow check valve either (i) between the returning circulator and the furnace (more difficult to do) or (ii) on the other end of the circulator (much easier to do), and how much distant should the flow check valve be from the circulator?

[NJ Trooper]

What circs are you using?

It might be as simple as replacing the circ with a model that has the internal flow check ...

Check valves aren't installed 'around' the circulator, they go in series with the piping. Usually at the discharge end of the pump.