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campbep · Joined: 06 Nov 2007 Posts: 5 Location: Norwich

The pressure in my mains pressure system keeps dropping to zero, despite me topping it up with water every day via the filling loop to bring the pressure back up. I have a conventional oil boiler with rads upstairs and wet underfloor downstairs. I have bled all the rads and there are no signs of any leaks. Any suggestions or help will be appreciated. Thanks

thescruff · Moderator Joined: 03 May 2003 Posts: 4632 Location: Bath

We need more info.

Boiler make model, Cylinder, cold water storage, anything that may be handy.

Check the Pipe through the wall from the pressure relief valve.

campbep · Joined: 06 Nov 2007 Posts: 5 Location: Norwich

Boiler - HRM Wallstar
Cylinder - Heatrae Sadia Megaflo
Cold water storage - ? There is no storage tank
Underfloor system - Unipipe
Have to cut the pipe from wall to see if it is dripping as at the moment it goes into a drain outside so I need to cut it just above the drain.
Have not isolated each circuit of the underfloor yet to see if one is leaking. All the valves on the manifolds appear ok and no leaks where the pipes enter the manifolds

thescruff · Moderator Joined: 03 May 2003 Posts: 4632 Location: Bath

Do the simple things first, like check the underfloor and any nuts etc when everything is cold.

Keep an eye on the pressure gauge when the boiler first starts to see if it goes above 3bar.

campbep · Joined: 06 Nov 2007 Posts: 5 Location: Norwich

Underfloor checked when cold and all ok
Filled system with water to bring pressure up to about 1.5 bar when system off and cold and pressure dropped by a third within 2 hours when the whole system was off.
No water leakage from PRV
Could it be an air leak? If so, how can I check for this and how do I remedy it?

thescruff · Moderator Joined: 03 May 2003 Posts: 4632 Location: Bath

No it would not be an air leak.

You are going to have to separate the system, starting by valving the underfloor off and testing that first.

Then repeat with the cylinder which could be more tricky unless you have valves on the primary pipes.

You could try pressurizing the system then turning the cylinder cold feed off, and opening the taps, any problem with the cylinder should take the pressure from the heating circuit as well

campbep · Joined: 06 Nov 2007 Posts: 5 Location: Norwich

Problem identified, the heat exchanger on the boiler has sprung a leak and water coming out as steam like a steam train!

Thanks for the advice

thescruff · Moderator Joined: 03 May 2003 Posts: 4632 Location: Bath

Thanks for the result, at least you don't have to dig any floors up Cool

campbep · Joined: 06 Nov 2007 Posts: 5 Location: Norwich

No floors to be dug up but this will be the third heat exchanger in 4 years!

thescruff · Moderator Joined: 03 May 2003 Posts: 4632 Location: Bath

Have you taken the issue up with the manufacturer.

It suggest there's no/not enough inhibitor in the system or the boiler is overfiring

AlanE · Posted: Fri Nov 09, 2007 7:25 pm Post subject:

There are 3 or 4 pieces of ceramic insulation in these if I remember rightly. Are they still in place correctly?