Easy radiator/three-way-valve wquestion

[phil1963]

I received a good answer to this question recently "When the boiler goes on at 5.30am I occassionally wake to hear a noise akin to to a soft "tap-tap" or creaking sound from the central heating system in my bedroom (on the first floor)."
However on examination the central heating is not yet switched to on (we have a warm house!!), so surely there should not be any heating of water in the pipes as the warm water should be going into the boiler and not the piping. Should I fear that the three-way switch has failed and is allowing a small amount of water into the pipes that then heats up and causes noises to be heard in the pipes? I had not noticed the radiators getting hotter as they are turned down to zero on the radiators thermometers, so they would come on anyway.
Do three-way valves leak a bit, and are they easy to repair? I should add that a new one was fitted but two years ago.

 

[jackthom]

Does the pipework from the boiler to the hot water tank run anywhere near the bedroom? That's all I can think of at the moment.

If the radiator valves are actually turned off there won't be any flow of hot water going anywhere near them.

 

[phil1963]

Jackthom,
The boiler is in the kitchen on the ground floor at the back of the house and the water-tank in the bathroom directly above it on the first floor. The "pinging" pipework is at the front of the house on the first floor, so a long way away. I am guessing that I have a three-way-valve that is allowing water through?

 

[TicklyT]

Could it just be some creaking and rattling from pipe expansion in the hot water crcuit is being transmitted through the heating pipes to the radiator, which is working like a sounding board?

It is not unknown for pipework installation errors to lead to a reverse flow in the heating circuit when hot water only is selected.