Question from T Shaw:
My gravity fed hot water system produces only a trickle of water at some hot taps for the first couple of minutes, then gushes through when the water becomes hot. Have you got any ideas of why this is happening?
Response from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
From your description there could be one or two reasons why this phenomenon is occurring. I think to narrow down the potential reasons a few questions need to be asked:
Is the domestic hot water (DHW) excessively hot? The point behind this question being, is the cylinder thermostat functioning correctly and turning off at around 60ºC? Overheating of the cylinder could result in the water within travelling up the safety vent pipe and cold water being introduced into the cylinder via the cold feed. Potential aeration of the cylinder and pipework could take place with a consequential air entrainment into the distribution pipework, which is released when the hot water outlet is opened.
Is the issue apparent with all outlets or just the same ones? It is possible that the tap washers are expanding or contracting excessively with the differing DHW temperatures and closing down the orifice of the tap. It therefore may be a consideration to change the tap washers.