Header Tank advice

[Cartboy52]

Hi there,

I need to put a new valve on the header tank of our central heating, as it won't shut off fully.

Have just ventured into the loft and noticed that the water in the header tank is hot. Steam is coming out of it, making the rafters above it damp. Looks like it's been this way for some time, as the rafters directly above the tank have white mold on them.

The roof is well ventilated (being slate with no felt).

Is the water in the header tank normally hot?
Can I put a lid on the tank to keep the steam in? (it currently has some planks of wood on it, but they have gone rotten)

Thanks

 

[bathjobby]

Put a working ball cock valve on to stop the tank filling. The level of water in the tank should be low, just covering the feed pipe at the bottom. Your increased height in water is causing you to over pump, hence the steam.