Closed CH System - Pressure Loss... likely places?

[Mike Dodd]

I was called around to my sister's to "replace some radiators because they're too small to heat the rooms".

In actual fact, the bathroom towel rail rad was straight across the boiler feed/return and the lock-shield was full open. That adjusted, and a first crude attempt to balance the rads appeared to solve most of her problems (even the particularly confusing one of the living room rad TRV turning itself permanently off, once the room was up to temp... go figure???, do TRVs require a certain pressure behind the pin-valve to work properly???)

Anyway, that said, she was explaining that she had to fill the CH circuit every day or so, and was "advised" by the installer "Anywhere up to the red line is okay" - that being 3-bar, the pressure at which the Pressure Relief Valve actuates, and dumps the water out of the relief pipe.

Having educated her in RTFM for the boiler (a Baxi 80) which indicates normal pressure 1-2bar, min 0.5, max 2.5 she's agreed not to go above 2-bar on filling.

But, the question remains, what is causing the pressure drop?

I've now got a container collecting anything from the pressure-relief valve, to check that that's working ok; I've been under the ground-floor (I job I really don't enjoy) and checked all the joints on the CH system

- no leaks evident. I've not yet checked under the upstairs flooring, since that's a much bigger job for another day. I've checked around the boiler and there's no obvious leak.

So, my question is (and I know there's not much to go on) - is there any likely "gotcha" on a closed system where I can look for a leak or anything?; I'm not competent to repair anything, but if I can spend my time finding the puddle of water, maybe I can help save her some cash when she needs to get an engineer / plumber in.

As always, any help gratefully received.

Mike

[cj]

Hi You don't specify the type of system you have as sealed systems these days normally suggest 'Combi ' boilers but conventional systems can be sealed. That said the task is still the same Find the leak! A few pointers .Have you had any work done recently (floors removed/refixed? Moved or relocated any large objects? Had a new carpet fitted? Think back to when the problem first started (if known) and try and relate anything done around that time. Moving a wardrobe caused a leak once when the new location crushed a badly fitted rad pipe in a bedroom. Carpet fitters (sorry to all good carpet fitters) have IME sometimes punctured a pipe whilst fitting edge trims or loosened rad conections causing a minor leak which the new carpet absorbs. The most common is creaky floor boards,you screw them down only to clip a CH pipe. All are a pain to locate.

HTH CJ

[Harry Bloomfield]

They can be very difficult to find....

It doesn't take the loss of much actual water to cause the pressure to fall.

One way is to drain the system and pressurise the system with air. Air can escape more easily than water, so you might be able to hear the air blowing out of the spot where the leak is.

[John Stumbles]

Have you looked at

(or if that wraps on your newsreader go to and navigate to the section "system_pressure_dropping")