Intermittent hot water
We have a system boiler and a relatively new hot water tank. On certain taps in the house I always get hot water, in fact too hot. On other taps and showers the hot water is intermittent. On some taps and one shower (not in the same bathroom) it only ever gets to tepid or warm, not hot. Not always, but usually if the pipes bang we get hot water. Generally I get hot water in the shower in the morning, but after about 10am it is pot luck. Sometimes when the water is hot in the shower it can change to tepid and back to hot again. Not all (if any) taps have non return valves, but a plumber told me to check the pipe coming out of the hot water tank when we get cold water: if the pipe was cold, it could be a non return valve issue. The pipe is always red hot. Any ideas?
Advice from 3 local tradespeople
Hi, because the hot outlet pipe from the cylinder stays red hot, the cylinder itself is likely heating correctly. That points more towards a problem after the tank, such as a faulty blending valve / thermostatic mixing valve, a hot-to-cold crossover through a mixer tap or shower, or a pressure/control issue on the hot and cold supplies. The fact that some outlets are very hot, some only tepid, and some fluctuate between the two strongly suggests either a mixing valve fault or a crossover somewhere in the system rather than no hot water being made. The banging also makes me suspicious of a valve or pressure issue. This needs to be traced methodically, starting at the cylinder outlet and then isolating mixer taps/showers one by one.
The issues you are experiencing with inconsistent hot water temperatures across different taps, ranging from too hot to just tepid, along with associated pipe banging (water hammer), are likely due to a combination of factors, probably involving a malfunctioning diverter valve, limescale/sludge buildup in the system, or faulty components within specific taps/showers.
There is more than one possible cause without looking and checking the instillation.
it’s a guessing game otherwise, My advice contact the previous installer or find a local engineer to visit.
