ᐅ Hot Water Recirculation Line: Is a Check Valve Required?

Hello Nordanney,

nordanney schrieb:
A hot water recirculation 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 about it).

In my opinion, what you have is not a classic recirculation line that would significantly increase primary energy demand. You turn it on and off deliberately; although these operating times probably add up by the end of the day, it likely does not have a major impact overall. Your plumber has therefore agreed on the supply temperature.

However, I wonder – although I am also a technical novice – what the actual benefit of switching it on for you is. The requested water would need to be heated to a set temperature first, meaning cold water also flows through the line beforehand, right?

Regards, Bauexperte

Bauexperte schrieb:

Although I wonder – but I’m also technically inexperienced – what exactly does activating it bring you. The requested water must first be heated to a set temperature, which means cold water also flows through the pipe first, right?

Best regards, Bauexperte

We don’t want to keep the circulation line running all the time either – that would really increase costs!
It’s true that when you turn on the tap, cold water comes out initially. However, in the bathroom, for example, it’s usually the case that you might first use the toilet and only then turn on the water (and warm water is already available!) or perhaps wet your toothbrush first, or…
In the kitchen it’s different, since a switch must be activated first. But that’s just a matter of getting used to pressing it when you’re already in the kitchen.
Overall, the situations where warm water is available from the tap when needed should clearly outweigh the others.

Bauexperte schrieb:
In my view, what you have is not a conventional circulation loop that would significantly increase the primary energy demand.

That’s why I asked at the beginning: Is it possible to get KFW support with a circulation loop, since the primary energy demand (at least in our case) clearly increases due to many losses from "unnecessary" heating. And that definitely has something to do with KFW, right?
We don’t have a circulation loop; we were advised against it from an energy efficiency perspective – which often annoys me because it takes longer for warm water to arrive, so I waste water while showering.

Hello Wastl,

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

Bauexperte, writing from the road

Wastl schrieb:
.... Our builder’s heating technician explained to me that having a hot water circulation line would disqualify us from KfW funding....

That is not correct. The decisive factor is the qp´´ value. Although this value worsens with circulation, it is acceptable as long as the required value is still met.
A circulation pump running continuously wastes energy. Time-controlled operation has proven to be effective.
Check valves or thermosiphons are not mandatory but are highly recommended!

Best regards