Water pressure problem

The water pressure in my central heating system frequently drops. After re-pressurising it, it returns to normal, but then the next time the heating is switched off, the pressure drops again. Any ideas?

I have a combination of old "cast iron" radiators as well as more modern ones. Could this be the source of the problem? It's been working fine for the last 4 years. Also, I've checked all the radiators and there doesn't appear to be any leaks.

Check your expansion vessel if you haven't already.

I have exactly the same problem, and I have all new readiators and boiler.
Question: How do you check your expansion chamber????
Help!!!!

How do you check your expansion chamber?

Click to expand...

Search the forum for expansion vessel and filling loop. There's loads of posts sept to nov 2003.