Combination boiler loosing pressure

[Lasitha]

Hi,

I have a Worcester Bosch Greenstar HE combi which is about 2 years old. When I first put heating on this autumn (about a week ago) I noticed that the pressure was very low. I toped-up the pressure, however, every

1-2 days, the pressure goes down again.

I called British Gas today and they left the boiler turned off and disconnected until tomorrow. They said, if the pressure goes down now, they will replace some part in the boiler (can't remember the name). If the pressure remains at the same level after 24 hours, they said that means I have a water leak and the only way to identify the source is to lift-up the floor boards. There are no leaks from the boiler or the overflow.

Are they right?. Isn't there another way of identifying the source of the leak (if there is one)?. The last thing I need is to lift the floor boards and find out there is no leak.

Thanks for any info.

Lasitha

[Newshound]

That will be the pressure relief valve. If this has lifted, they are often reluctant to seat properly again (perhaps lime deposits?)

Presumably this means they have isolated the boiler from the radiators and hot taps.

Much as it grieves me to say so, they could be right. Although if the expansion vessel has gone flat or has a leaking diaphragm then the pressure relief valve will come into play. See if they use a bicycle pump and a tyre pressure gauge.

[Lasitha]

Thanks for that.

The pressure hasn't gone down in the last 20 hours or so (when they disconnected it). So it looks like the boiler is OK.

I really don't want to start taking floor boards out since I have wood floors downstairs. If the leak is downstairs (I guess if it is upstairs, water marks would show up through the celing), can I not simply keep toping-up the pressure?. Any water would leak out to the ground.

[Ian Chard]

I'm no expert, but the combi I had in my last place lost pressure over the course of a few weeks, and I topped it up when it got too low.

I had three failed pressure vessels in five years, and the guy that replaced the last one said that repeatedly topping it up with fresh water increases the corrosion inside the vessel due to the fact that it was highly oxygenated.

Don't know if that's bollocks or not, of course!

- Ian

[Ed Sirett]

Try the SealedCH FAQ.

[Lasitha]

The BG engineer finally turned up today and said he is 100% sure the problem is not with the boiler. So he is going to order some chemical which seals the leak.