Central Heating Leak

50Twuncle

Also - the second plumber today - topped the water pressure up to 1.5 (obviously cold) and told me to let him know on Monday whether it had dropped ...
Obviously, it will drop - but what will we learn from this ?
Without the heating on - it may drop a little - but not as much as with the system fully pressurised ....
The boiler is serviced annually before anyone asks - last serviced in January !!

50Twuncle

Myser wrote: »

Before you go lifting up floorboards, check the Pressure Relief Valve (PRV) discharge pipe and Expansion Vessel (EV) as mentioned by macman.

Then, inspect all the radiator valves and bleed nuts carefully making sure they are tight.

If your radiator pipes are copper, look for oxidisation (green marks) on any pipes.

Just one rad (hallway) shows signs of slight surface rust around the connection - dry old Copper oxide staining (have always been there) no signs of any damp - no signs of damp on any ground floor ceilings - so presume any leak (if ?) will be below the ground floor ?
joints all tight .. as are bleed nuts

Myser

50Twuncle wrote: »

so presume any leak (if ?) will be below the ground floor ?
joints all tight .. as are bleed nuts

Not necessarily as small leaks around radiator valves and bleed nuts can evapourate before you notice. Not the case in the summer though when the central heating won't be on, however, water will not be flowing through the central heating loop so again hard to tell.

keystone

50Twuncle wrote: »

so presume any leak (if ?) will be below the ground floor ?

You are not paying attention.

1. If the EV needs constant topping up there is something wrong with it.
2. Place a small bag over the end of the PRV outlet pipe (that's the copper one on the outside wall) and tape it there and make sure pressure is correct. If the PRV is passing you will have water in it and that tells you its the PRV.
3. As already said it could be a leak between DHW and CH sides of the HEX. Your RGI needs to check that - unfortunately you can't.

Only when you've addressed these and drawn a blank do you start to think about ripping up floorboards.

Cheers

macman

Your second 'plumber' (you need an RGI, not a plumber) seems equally clueless. What is the point of topping up a system that you already know is leaking, without doing any diagnostics to find the source of the leak?
You seem intent on ripping up the whole house rather than a simple 5 minute DIY check of the PRV.

keystone

macman wrote: »

Your second 'plumber' (you need an RGI, not a plumber) seems equally clueless. What is the point of topping up a system that you already know is leaking, without doing any diagnostics to find the source of the leak?

In his defence, albeit knowing there is a pressure loss, perhaps he is just trying to find out exactly how much pressure is lost over a given number of hours (rather than just an unquantified, airy fairy "it's losing pressure") to assist his diagnosis process.

You seem intent on ripping up the whole house rather than a simple 5 minute DIY check of the PRV.

Quite. Cart is best placed behind horse.

Cheers

50Twuncle

macman wrote: »

Your second 'plumber' (you need an RGI, not a plumber) seems equally clueless. What is the point of topping up a system that you already know is leaking, without doing any diagnostics to find the source of the leak?
You seem intent on ripping up the whole house rather than a simple 5 minute DIY check of the PRV.

OK - pressure has dropped in the 20 hours since it was pressurised to 1.5 bar - it is already down to 0.8 bar
This is far worse than before...
You state "if the EV needs constant topping up...."
I assume you are talking about re-pressurising ?
if so - yes, annually...
When I am topping up the boiler with water - where is that going ?

southcoastrgi

Have you done the bag over the pipe as KS suggested ?

Humour me, when they re-pressurise the EV how exactly do they do it ?

keystone

50Twuncle wrote: »

OK - pressure has dropped in the 20 hours since it was pressurised to 1.5 bar - it is already down to 0.8 bar
This is far worse than before..

Have you checked the PRV outlet? With that sort of loss then, if it is the PRV, the bag is probably not necessary. You'll be able to see that the wall/ground is wet and feel the water in the open end of the pipe. Can you?

You state "if the EV needs constant topping up...." I assume you are talking about re-pressurising ? if so - yes, annually...

Yes I did. Possibly not that then. I got the impression from your other posts that it was much more frequently than that. Another test for the EV. When you have the pressure at 1 - 1½ bar and then turn the heating on does the pressure suddenly shoot up to approaching 3 bar? If it does thats the EV gone and if it does go that high then the PRV will have lifted anyway.

When I am topping up the boiler with water - where is that going ?

OK. I'm probably going to regret this but there is a way you can check the HEX even though I said there wasn't because I suspect it would be better if your heating engineer did it for you. This evening pressurise to 1 - 1½ bar. Turn boiler off. Isolate the boiler by closing the valves on the flow and return. Go to bed. In the morning check if the pressure has fallen. If it has then the leak is internal to the boiler.

Cheers

macman

Why don't you just check the PRV overflow as already advised several times? This is by far the most likely cause.
If it's depressurising at that rate then the leak will be obvious below the pipe. One minute's work.