multicoil cylinder problem

[JEMHOWE]

This is an odd one, read previous similar posts but nothing quite fits.

Have a 3 coil cylinder, rayburn solid fuel convection, central heating pumped and solar coil pumped. With the boiler off, rayburn in and solar off the main cold water storage tank keeps overflowing. If I shut the gate valve off from the tank to the bottom of the cylinder the expansion pipe drips - so I know I have a problem in the hot water circuitr. However, both header tanks for the rayburn and boiler are lower than the cold water tank. Why would a hole in the coil push water up into cold water cistern and not into the relevant independent header tank. It doesn't make sense to me.

Any ideas what is happening? I'd say it was definately a hole in a coil except that the cylinder was new 2 years ago. Problem has been steadily got worse. What else could it be?

Thanks for your time

 

[spraggo]

I would suspect that you have a faulty mixer tap installed. Does the water drop in the small header tanks when the cold water tank overflows/expansion pipe drips, is the solar panels higher than the water tank?.

 

[JEMHOWE]

Yes thought about the mixer tap - do you mean it is pushing cold water into sytem via the tap. However, if no one is using anything in house, how could it happen?

The solar panels are lower.

I have not found any lowering of small header tanks. Where can all this extra water come from. Thought it could be exopansion but this could only be about 4litres of a 200litre cylinder.

 

[spraggo]

If a mixer tap has a fault ie, a pin hole in the casting the cold water mains will push the hot water up into the head tank via this hole whether the mixer is used or not. Try isolating the supplies to the mixer tap.

 

[JEMHOWE]

Yes I unmderstand this now, I assumed you meant afault in the valves not the body of the casting- that would explain it and I will try isolation.

If there was a coil problem I'd surely notice discolouration in hot water.

Thanks

jem

 

[JEMHOWE]

Thanks for help - you were right. With no water on in house went to all mixers and put screwdriver againsta nd ear on handle. Could hear water flowing through shower mixer tap. Well done and thanks for help.