Possibly, though unsure what that path might be. I expect some leak thru the small check valve I used. But this only brings hot water to furthest end of plumbing and then its turned off. So it only 'circulates' for those few seconds.
There shouldn't be any pressure differential or path that would cause reverse flow more than before pump added? Only way I can see, if say running water with pump off, check valve requires pressure (non spring loaded) to stay closed. But by that time line pressure has dropped, I would have to do repeatedly to get water movement in reverse.
It may though, I just don't know it. I tried to see all the sceneries-and what/why folks are doing in some of the more elaborate systems. All I wanted was hot water in the bathroom. I haven't noted any extra run time of water heater or lukewarm water. The added recirc pump in our home works same way. Basic small pump under sink between hot/cold. Single non spring loaded check valve.
But wouldn't be the first time I have been to dumb to know I cant do what I did.:)
