hot water in header tank

[johnny37]

My in-laws have their central heating really high (30c). I noticed the header tank is full of warm water. Is this normal. If not what is the prob and how much should I pay to have it repaired.

[pussnboots]

This must be a normal C H boiler and not a "Combi" hence the header tank.If you look at the top of the hot water cylinder you will see a 22ml pipe which feeds the hot water taps.This pipe will branch off and go up to the header tank in question and loop over the top. It is the expansion pipe and its purpose is to allow excess hot water to go into the header tank.If this expansion pipe was not there the hot water cylinder would burst under the pressure of the water being heated. IT IS QUITE NORMAL..Is there a separate thermostat on the side off the hot water cylinder which could be lowered.

[knobbynonuts]

You should not to have to pay anithing

[Jay70]

This can happen if your pump speed is set too high or if the pump speed is correct but the system resistance is too high, which I think is the case here. If you live in a hard water area it's amazing how much lime scale can build up in a heating system and related pipework. It sounds like the resistance is become higher over time which is why your in-laws have been increasing the thermostat gradually to compensate. They have a smaller flow of hotter water as opposed to a large flow of cooler water in their system to give the same heating effect. As for the cost it depends on how much of the system is effected. I live in a hard water area (South Bucks) and have got a water softener fitted now) to help combat this.