Finding a leak in a Central Heating System.

Yep - chust looked at the installations instructions. That makes it even easier

Don't forget, tho' - the boiler must be turned off all the time these valves are closed.

 

Can you confirm you actually mean you shut off BOTH flow and return taps on the boiler? If you only closed ONE tap, then we are no further forward on this test...

But, if you closed BOTH and the pressure still dropped by a quarter bar, then that suggests your leak is from within the boiler.

Is that good or bad news? Could be. Either.

It might be as little an issue as a safety release valve allowing a trickle of water through. This is the valve that is meant to pop open if your system reaches 3 bar and allows the excess pressure to escape (and from your description, that may well have been the case). What happens then is that is doesn't shut properly afterwards and allows a steady leak afterwards.

You can check this easily by locating the 15mm copper pipe outside the house that allows this discharge - it should be pointing downwards safely at the ground. ID this and then loosely tape a clear plastic bag over the end so's you can monitor any discharge.

If it turns out to be a leaking pressure release valve, then that's a pretty cheap thing to replace. But you would only do so after working out what else is wrong with your boiler.

Now that you've carried out that test and the pressure is set to ~1 bar, what happens now? How does the boiler behave when turned on and what does that pressure gauge do?

 

No need - I think your test is pretty conclusive.

That's good news - it looks as tho' your pressure release valve is letting by after it was forced open when the pressure hit 3 bar during your current issues...

They tend to do that - they rarely seal off again afterwards - a real pain.

At least it suggest your leak is an easy issue - MUCH better than a hidden pipework leak or a blown heat exchanger or summat.

(PRVs are around £30 and can be replaced in a half-hour).

You need a GasSafe - (a) to replace that PRV and (b) to sort out your pressure issues. (b) needs to be done before (a) or else you may end up 'leaking' another PRV...

 

The pressure issue should have nothing to do with the rads.

Yes, you explain you've had pressure fluctuations which you suspect has tripped the safety release valve, and it's now dripping and slowly losing you pressure.

Emphasise that the original fluctuating pressures issues have not been resolved either - that's the main thing.

 

Fingers crossed

 

Fab!


(Keep an eye on that gauge over the next few weeks. In between drinking and eating lots...)

 

Kettling is usually a scaled up hot water heat exchanger,restricting flow, & descaling them isn't 100% effective as the waterways within them are small, so a new one is needed.

Here a photo of one that's scaled up.

 

What type of boiler is it, Trudy?

(Oh, Happy Fixed Boiler for a Short Time, by the way... )

It does sound as tho' the heated water isn't being taken away by the flow fast enough, and this could well be due to scaling as KIAB says. The layer of scale insulates and partially blocks the waterways, so the water heats up very rapidly before the overheat 'stat cuts in and shuts the flame orf.

I'm not sure is descalers would work, but it's surely worth a try? Check out Sentinel X200 - our hosts stock it.

If your boiler has temp controls, try turning it down a good bit - if you can slow down the heating rate, perhaps it'll have a better chance of getting rid of the heated water before it 'trips'.

Anyhoo, what type of boiler? Combi? System? Make and model?

 

I knew old plumber who ue to remove the HW heat exchanger & soak it in Kilrock-K Descaler, took several applications to remove the limescale, never 100% effective though.

 

Worth a try for £20 tho', as the alternative is very costly...

 

Robert Dyas sells the larger 400ml bottles.

http://www.robertdyas.co.uk/kilrock-big-k-multi-purpose-descaler-400ml

 

I meant to add to her CH system!

 

It's the HW heat exchanger that is scaled up, & that is the cause of kettling when she turns on tap.

Wouldn't be a bad idea to give CH side of system a dose of cleaner, but you ideally need a filter (Magnaclean Pro 2) to catch the dislodged crud rather than continually recirclating it.

 

Oh! I see... The domestic water side of the exchanger?

Argh, stuffed then...

Trudy, does this heat 'cycling' and kettling occur with the CH side too? Or chust when you draw water? (And is it a combi?)

If it's a combi, then drawing DHW will have the boiler running flat out, so I wouldn't be surprised if kettling occurred here from scaling on even the 'system' side of the boiler.

Anyhoo, I suspect you really need a cove out to diagnose, Trudy.