Hello All.

As per subject line, I am having trouble drawing satisfactorily hot water upstairs in my house. Downstairs, the kitchen and bathroom hot taps supply water that is plenty hot enough. Upstairs (shower, bath, basin taps), the hot tap/shower water temperature is often lower than is desirable (but sometimes works fine). A notable aspect of the problem is that running a cold tap can cause the hot taps (separate hot and cold, not mixers) or shower temperature to increase.

My mains pressure is 3-4 bar (varies). The pressure is high-ish, but within spec for the boiler. However, noting the temperature-increasing effect of running a cold tap, I can't help but think that the problem is pressure-related and more particularly, that it relates to the pressure change when hot water is drawn. Upstairs, with a head of water higher than downstairs, the percentage pressure drop, on opening a tap/valve, will presumably be lower than for a downstairs tap/valve. However, when a cold tap/valve is opened somewhere in the house, boiler inlet pressure is reduced and then, presumably, the percentage pressure drop when an upstairs tap/valve is opened is increased. Might it then be worth my while trying a pressure reducing valve on the boiler cold water inlet?

To be clear, the problem is not that the upstairs taps/valves allow a flow that exceeds the boiler's heating capacity. With a cold tap running, I can get a greater flow of hot water from an upstairs hot tap than at *any* setting of an upstairs hot tap, running alone.

Advice appreciated.

Regards.

Terry.