Pressure Relief Valve

[skeeterm5]

Hi

one of the pressure relief valves on my hot water cylinder is dripping. Can I fit a replacement using plastic plumbing pipe or does it have to be fitted to copper piping?

The valve is on the cold water mains inlet before it reaches the hot water cylinder.

thanks

S

[Rickyy]

Pretty sure it must be copper. Also it will be dripping for a reason. The expansion vessel could need replacing.

[Gingerbread Man]

If you replace it, why do you have to change the plumbing?

If it's the incoming main, is it the pressure reducing valve for the mains pressure? As Rick says, it'll be dripping for a reason.

[caziques]

Yep, depends on the way the cylinder is vented as it may be designed this way.

A few litres of water have to be accounted for as a cylinder heats up due to expansion.

It may be a cold water expansion valve.

[Arthur Jackson]

Yes, discharge pipes *must* be metal. (There is an exception, but it doesn't apply here)
If the pressure relief is running then it's either doing it because the expansion has failed (Air bubble or vessel diaphragm/air charge loss) OR the Pressure Limiting Valve has failed. Both pressure reliefs on an unvented cylinder are connected to the pressure in the cylinder itself, but one is set lower than the other.

[skeeterm5]

Thanks all.

Have decided it is prolly best to get a plumber in.

S