Warm water circulation line: Is a check valve required?

Hello experts,
I have a hot water circulation line in my newly built semi-detached house, which I want to circulate only on demand using a Circon circulation controller. However, when the pump is off, the return line above the pump heats up.

The heating engineer believes that the pump must always run, so the problem cannot occur.
I don't think that makes sense and I believe I once heard that a check valve is required in the circulation line.

It would be great if someone could clarify what is required here. Thank you!

May I ask if you meet a KFW standard? Our builder (their heating technician) explained to me that you would not receive KFW funding with a hot water circulation line. It would be nice to know if it would have been possible after all. Unfortunately, I have no solution for your problem.

The hot water circulation line is nothing special. We have it too, controlled by motion sensors in the bathrooms and by a switch in the kitchen. The KfW is not interested in that either (aside from the fact that they never find out).

@nordanney That sounds interesting. May I ask how you wired it electrically? Are there one or two pumps (one for the bathroom circuit, one for the kitchen circuit)? Thanks and regards klblb

@klblb It is only one pipe, which also has only one pump. The plumber and the electrician took care of the details (rough installations are just finished). I hope that it will work out that way too.

Hi
when I did my installation on my own, I planned a timer switch for the circulation pump. Running it continuously is not necessary and not cost-effective. I installed a check valve in the circulation line.