Why does the hot water pressure drop?

Do you know that? When turning on hot water in the shower or on the sink faucet, the jet is painfully lax or suddenly ebbs significantly after the first full burst. Let's take a closer look at what this can be and what you can do.

The thing about the hot water pressure

How high the water pressure in your drinking water pipe system is depends on the one hand on the pressure provided by your local water supplier and on the other hand with more or less pressure-changing factors in your residential building. Water supply companies usually deliver the water at a pressure of 3-4 bar. Depending on how high your residential building or rented apartment is, this value can decrease a little.

If the pressure of cold and hot water at the taps in your house is equally strong or equally weak, that shouldn't be a cause for concern at first. However, if the pressure is clearly too low when drawing off hot water, this can indicate damage to the pipeline or drinking water heating system. The following causes are possible:

  • Line damage
  • Check valve is stuck
  • The faucet is calcified

Line damage

If the hot water pressure is permanently weak at all draw-off points, in the worst case this could be due to a leak in the hot water pipe. If water escapes at one point, the pressure of the (still) incoming hot water is also reduced.

In order to localize a possible leak and save high costs for professional leak location, you can first look for damp spots on exposed pipes and on the walls. The leak may also be on the upper valve of the central hot water tank. Also, check to see if you can hear hissing noises from toilet cisterns.

Check valve is stuck

The check valve of the central water inlet is often the reason for pressure fluctuations in the drinking water system. There is a heightened suspicion of this component if there is always a relatively abrupt drop in pressure at the tapping points shortly after opening. The check valve, also known as the KFR valve (combined free flow valve with non-return valve), is located directly behind the water meter on the central water connection.

Possibly it can be used again simply by turning it up and down once or several times. Otherwise it must be removed and decalcified, and replaced if it is too worn.

The faucet is calcified

Do you have the problem with insufficient hot water pressure perhaps only at one tap, for example in the shower or at the kitchen sink? Then it can simply be due to the faucet and a calcified cartridge. Even as a layperson, the cartridge can be removed and decalcified or replaced by yourself.