Boiler pressure

[ailie]

My combi prssure needs to be topped up quite often now, what's that a sign of? A big bill?

[paul'1cru]

it sounds like u have a small leak somewhere on your heating system if you have to top it up and its getting more and more then the leak is getting worse. how old is the combi ?

[ailie]

Thanx paul. Boiler probably 6-7 yrs old. Is that maybe the age things start goin wrong?

Yes there is a bit of a leak of dirty water from under the boiler..a tablespoon every week maybe.

The other thing goin on is I think a rad is now colder at bottom than the top. How do I reverse bleed...joke!

I suppose this started when I had to bleed 2 rads quite often. Then I had to have a new plastic handle bit fitted on the top up valve cos the plastic on the old one had broken.

[stephen2504]

ive got same problem with my combi pressure keeps going down and there is a small leak from inside the boiler dont know what it is and i cant afford to get it looked at as ive been made redundant and cant afford it i just keep turning the pressure back up hope we find a simple solution

[ailie]

Thanx den, I know the leak is under the boilerbut what is going on with the rads hot at the top & cold at the bottom? Is that a massive air bubble?

[terence7556]

its a sign they may be sludged up.
drain it and take it in to the garden and hose the sludge out. if the water is nearly black and lumpy then the system is dirty especially if say more than two rads require the clean.it needs a clean out before putting fresh inhibitor in.
probably before you sort out the leak

[ailie]

Terence, I'll get onto that . I had a 500 bill at my last house when the exchanger went & pump neaded replacing cos of muck so I don't want that whole scenario again.

[heathfield]

A combi boiler uses a ''closed system'', meaning that as the water heats up and expands, there could be nowhere for the water expansion to go. So the expansion is taken up by an ''expansion vessel''. This is a small cylindrical tank inside the boiler. One half is connected to and filled with water from the heating system and the other half is filled with air under pressure. There's a flexible diaphragm between the two halves. It's not uncommon for a leak to develop in this diaphragm, and a continual drop in pressure with no signs of a leak from pipes or radiators is a symptom of this. If that's what it is, a new expansion vessel is the only answer.

[ailie]

Heathie, that made me concentrate! Thanx for that idiots guide. I now stand a fighting chance of understanding what's up when it's diagnosed