Too long lead time for hot water?

If you have to wait forever for warm water to come after turning on the tap, it can be quite annoying. And also a reason for complaint when living in a tenant relationship. Too long lead times can be for various reasons. Nevertheless, certain standards and laws apply in this regard.

What causes the hot water lead time to be too long?

Ideally, you would like to get hot water from the tap or shower head immediately when requested. However, this is by no means always the case. The fastest way is with decentralized water heaters such as boilers or instantaneous water heaters, which are installed very close to the respective tap.

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With centralized hot water preparation methods, it can take some time for the water to be expelled at the desired temperature. This is related to the following factors:

  • Length of the pipelines
  • Inner diameter of the pipelines
  • Thermal conductivity and storage capacity of the pipelines
  • Insulation of the pipelines
  • Throughput of the extraction valve
  • Pressure conditions in the water treatment plant

When looking for the cause of an unusually long hot water lead time, there are a number of things to consider. As a homeowner, you should first ensure that the pressure conditions in the drinking water pipe network are correct. If there are disparities here, the water reaches the tapping points that are further away from the hot water preparation system (usually those on the upper floors) with too little pressure. In this case, hydraulic balancing may have to be carried out by specialists.

Another thing is the nature of the drinking water pipelines. Length, material and thickness largely determine the lead time, but also the completeness of the circulation and the water throughput of the individual fittings. Replacing fittings with models with a higher throughput can reduce the hot water lead time.

How long can the hot water lead time last??

As a tenant, you have quite clear rights with regard to the hot water lead time, which can be traced back to DIN standards and tenancy law. There are also some precedents in which tenants were able to obtain a rent reduction of 5% monthly due to excessively long hot water lead times.

According to DIN 1988-200, the standard is that after a maximum of 30 seconds when the tapping point is fully open, a water temperature of at least 55 ° C must be reached and after 15 seconds a temperature of 40 ° C. In addition, according to Section 535 Para. 1 of the German Civil Code (BGB) that the landlord must give the tenant the rental property "in a condition suitable for contractual use and keep it in this condition during the rental period". What is considered "suitable " in the individual case is always based on specific agreements in the rental contract or on the current technical standard.