We have a Vaillant Ecotec combi boiler in the loft. When showering, hot water pressure is fine. But if someone opens any other hot tap in the house, it massively reduces the hot water coming into the shower (obviously because now two taps are sharing the same hot water). Is there a cost effective way to allow both taps to run at the same time but the pressure to remain constant so it doesn't interrupt someone's shower? It's very annoying if someone else in the house decides to use the hot kitchen tap while someone is showering.

2 Answers 2


There are several ways to fix this problem...

  • Increase the supply pressure of the incoming water feed.

  • Increase the diameter of the piping feeding to the shower.

  • Install flow restrictors in the shower head and the kitchen faucet so that they share the available pressure and flow at lower levels and thus less interaction for the existing piping and delivery pressure.

  • Using restrictors is the only practical solution, the others are much more economically disadvantageous for SOMEONE.
    – HerrBag
    Apr 5, 2013 at 12:24
  • If the shower is much further away from the boiler than the kitchen, a point-of-use heater in the bath would increase local hot water, assuming cold water flow is sufficient.
    – HerrBag
    Apr 5, 2013 at 12:28
  • @HerrBag - Yeah, my options 1 and 2 could be considered tongue in cheek. I meant them as serious options and listed them in order of low to higher practicality.
    – Michael Karas
    Apr 5, 2013 at 16:44
  • @HerrBag - In most installations the cold water pressure at the house entry decides the static pressure throughout the dwelling. Localized hot water sources can help in cases where the piping sizes for the cold water flows is larger than the hot water part of the system. You do make a good point regarding whether the hot water feeds to the shower share flow from other up stream demands such as the kitchen sink.
    – Michael Karas
    Apr 5, 2013 at 16:55

Your boiler and probably your piping also do not have sufficient flow rate to allow hot water distribution from two taps. A possible fix is to split the cold water supply in the kitchen and then install a separate compact kitchen boiler for hot water in stead of your current boiler in the loft.

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