Warm water circulation line: Is a check valve required?

Hello Nordanney,

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

In your case, from my point of view, it is also not a classic circulation line that could significantly increase primary energy demand. You switch it on and off intentionally; although these switching times probably add up to some extent by the end of the day, overall it probably does not weigh heavily. Flow temperature. Therefore, your installer agreed. I wonder though - but I am also a technical novice - what actually switching it on brings you. The requested water then also has to be heated to a set temperature, meaning that cold water also flows out of the line beforehand? Rhenish greetings

Although I wonder – but I am also a technical beginner – what a remote activation really brings you. The requested water then has to be heated to a set temperature first, meaning that cold water also flows from the pipe beforehand?

Rhenish greetings

We do not want to keep the circulation line running around the clock either – that would really cost a lot of money!
It’s true, when we immediately turn on the tap, only cold water comes out at first. In the bathroom, for example, it’s rather the case that maybe you go to the toilet first and then turn on the water (and warm water is already there!) or maybe you wet the toothbrush first or...
In the kitchen it’s different, there you have to press a switch first. But that’s a matter of getting used to when you’re already standing in the kitchen, pressing the switch quickly.
Overall, situations should clearly predominate where warm water comes from the tap when you need it.

In my opinion, what you have is not a classic circulation pipe that could significantly increase the primary energy demand.

That is why I asked my initial question: Is it possible to get KFW with a circulation pipe, since the primary energy demand (at least in our case) increases significantly because many losses occur due to "unnecessary" heating. And that does have something to do with KFW, right?
We do not have a circulation pipe; it was advised against from an energy perspective—which annoys me quite often because it takes longer for warm water to arrive, and I therefore waste water while showering.

Hello Wastl,

based on my experience so far, it is not possible to take advantage of discounted loans from KfW for the reason you mentioned => higher primary energy demand.

Building expert, on the go

.... I was explained by our house builder (their heating technician) that you wouldn’t get KFW funding with a domestic hot water circulation line....

That is not correct. The decisive factor is the qp´´ value. This does worsen with circulation, but if the required value is still achieved, it is okay.
The circulation pump running continuously is a waste of energy. Time-based controls have proven effective.
Check valves or thermosiphons are not mandatory, but very useful!

Best regards.