Worcester Greenstar CDi 30 boiler - loss of pressure

14 Jan 2012
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United Kingdom
I am having to re-pressurise the boiler every few days, although it does still work even though the pressure has dropped to near 0 bar.

Can anyone advise how I can find out if the cause is a leak in the radiators / pipework, or a problem with the boiler itself?

I have tried using Fernox to seal the leak, but it only works temporarily.
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check the discharge pipe, should be outside, often about 1m below the flue.
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I am having to re-pressurise every day now!

I believe I have eliminated the pressure relief valve as the cause. I tied a bag to the discharge pipe 2 days ago, but it has remained totally dry.

I have checked all the radiators and exposed pipework for leaks - nothing.

There is no air in any of the rads.

A brief visit from a plumber who was attending a neighbour also eliminated the expansion tank.

That only leaves another boiler problem, or a pipe under the ground floor leaking - which is concrete! I have assumed this is less likely because the rads don't need bleeding (but this may be misguided)

Any further ideas before I dig up the floors?
I have the same boiler and had the same problem. Turned out to be a leak on a plastic compression elbow joint under the living room floor. Sadly, it is likely to be a leak somwhere. Get a good heating engineer or plumber to trace the fault.
The pressure problem still persists, so I need to trace the fault. I was given some advice to close the flow and return valves to determine if the boiler is the source of the problem.

If I do this, is it still OK to use the boiler for hot water, and should I also leave the CH 'on' (ie leave it to come on / off as programmed)?

The boiler is a Worcester Greenstar CDi30
Turn the isolation valves off overnight before you go to bed, if your pressure has dropped when you wake up in the morning steel yourself for a new heat exchanger, I've done quite a few recently.
I had exactley the same problem. Turned out to be a plastic isolator valve leaking under the ground floor. The valve (not fitted by me)fitted wasn't rated temp' wise for central heating, just domestic hot water..hence the valve seals leaking.
I am only a diy plumber and the fault wasnt hard to find so give it a go yourself..you may save some money.
If the leak is upstairs you would probably have noticed a wet patch somewhere on the ceilings.
Lift some ground floor floorboards and have a peek. Look for anything leaking.

My problem is now fixed. I called in a plumber to isolate the groundfloor rads, and after 2 weeks the pressure was still fine. As there was no sign of a leak downstairs, I had to assume the pipework in the concrete slab was leaking.

For peace of mind I took the decision to have the downstairs rads replumbed from the first floor - I could have paid to trace and fix the leak, then find I had another one in the future.

I took the opportunity to move a few rads at the same time and replace with new ones. Its all working now, and very cosy it is!

Thanks again to all for their advice along the way.

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