Retrofitting a hot water circulation line

Allowing the hot water to circulate in the pipe system is convenient and sometimes mandatory. But what if the management requirements are not met in an older building? Retrofitting appears to be very complex at first, but it can also be solved cleverly.

Options for retrofitting a hot water circulation line

In order to always have the warm drinking water immediately available at the taps in the house and to prevent legionella contamination, a constant or. regular circulation through the central heater is necessary. Corresponding cable routing is required for this. Normally, in addition to the hot water riser and the return line from and to the storage tank, a third, as short as possible return line is installed parallel to the riser.

With a circulation pump intermediately connected therein, the hot water can then run from the memory to the removal points and pump back into memory through the circulation return line, where it is repeatedly heated.

Whether the hot water circulation is needed with its energetic additional effort depends on two factors:

  • Size of the drinking water heating system
  • Individual claims in PUNCTO water readiness

According to DVGW, due to hygiene technical reasons, the rule is that in case of drinking water heating large plants - so those from a storage volume of 400 liters and from a pipe section volume of 3 liters - a circulation must be installed. For small systems with correspondingly smaller storage and pipe section volumes, it is the responsibility of the homeowner whether he wants to make the comfort of the constant warm water readiness through the circulation.

That is why there is by no means a circulation line in every average single-family house (older year of construction). Relocating them afterwards is time-consuming and should only be considered if extensive renovation measures are pending anyway. In addition, it should be ensured that the path for the circulation line to the storage tank is sufficiently short - standards for this are specified in DIN 1988.

Alternative possibilities to complex pipe installation

There are definitely alternatives to tearing open the walls completely: With a decentralized instantaneous water heater in the bathroom, for example, which is integrated into the existing hot water pipe. It can bridge the still cold tap water until the hot water arrives from the storage tank and also ensure the minimum temperature required in terms of hygiene. But be careful: so that the device does not overheat when hot water is supplied directly from the storage tank, it must be thermostatically regulated.

Another clever option is to implement the circulation return line in the riser itself using inliner technology. This not only saves a lot of structural effort, but also saves a lot of space for ducts and insulation. The polybutene circulation return pipe in the hot water riser also practically results in much lower heat losses.