Vaillant boiler leaking water

[RedEarth68]

We have a Vaillant Turbomax Plus 824E that was fitted in 2003 and has been working fine since. But recently I noticed water seemed to be dripping from it - and today I opened the front and saw that the water guage has filled up to past the red danger area! Whenever I've had to fill up the water before I've never gone beyond the green area - now to see it so far round to go beyond the red area is really shocking. I am afraid something awful will happen - can you tell me what's wrong? We haven't noticed any problem with getting hot water and the central heating works fine. But now I am afraid to turn on a hot water tap in case we do some irreparable damage.

Please help!

 

[gas4you]

Check that you have the filling loop turned fully off.

If you mean that it goes into the red when the rads are on then you need to check the expansion vessel. See FAQs.

 

[RedEarth68]

Yes, I checked and I hadn't tightened the key that fills water into the system well enough!

Thanks for your reply!