Hot water circulation via the cold water pipe - that makes sense?

There are two connection options for realizing circulation in the hot water system: on the one hand the classic one at medium storage height, on the other hand via the cold water pipe at the lower end of the storage tank. Sometimes the latter variant makes sense - especially with high purchase quantities.

What the hot water circulation via the cold water pipe is all about

Letting the warm drinking water circulate in the pipe has the following advantages:

  • Avoidance of the formation of biofilms and bacteria
  • Always immediately available hot water at the taps

If you want to keep the risk of infection with Legionella as low as possible and benefit from the convenience of instant hot water, you can opt for a circulation system.

Today, an electric pump is usually used for this, which controls the hot water and pumps it through the pipe system as required. If hot water is drawn from a tap, water must flow from the cold water supply line into the hot water storage tank and be heated to the set target temperature.

Classic middle connection for smaller storage / purchase quantities

So that only the warmest water from the top of the tank is tapped as far as possible from the pipe system, the connection pipe is usually located roughly at the middle of the tank. As a result, only the upper part is covered by the circulation movement and the lower, colder water layer is largely left alone.

This is always economical when it comes to a smaller storage tank of 100 to 200 liters from which generally only small amounts of hot water can be drawn. For example, in a single-family house with normal hot water use with daily, not excessively long shower runs for 3-4 people. The incomplete mixing of the storage water then results in fewer heat losses.

Cold water connection for larger storage tanks / purchase quantities

Placing the circulation connection in the lower area of the cold water inlet of the storage tank means that not only the upper part but all of the storage tank water is mixed during circulation. This means that no temperature layers are formed.

In itself, this is more wasteful of energy, but makes sense for larger purchase quantities. Because if a lot of hot water is needed all at once, the water will remain consistently warm until the end. This connection variant is therefore suitable, for example, for large storage tanks in the shower systems of sports clubs, where the entire storage tank is often emptied in one fell swoop after training.