Systematic method for locating CH leaks?

Caveat: I live in Switzerland, so installations may be different, but I hope the logic won't be...

In July I bought a 23-yr old house with a gas-powered, closed (ie pressurised), CH system the same age. The previous owner had said that from time to time, it was necessary to put the pressure back up (manually, through a hose connected to mains).

When the radiators were installed, they were directly attached to the pipes (underfloor, ie not running round the walls). That is: no way at all to isolate one rad from the circuit. So when I started redecorating my son's room, I drained, removed, painted behind, etc - towards the end of September. When I replaced the radiator, refilled, bled and turned on, the boiler (Chaffoteaux et Maury, Celtic TIG 20 BF) started playing up (wouldn't start, loads of bubbles, etc).

Called out the people, who tinkered (I was at work, so not sure how), and everything seemed OK. That said, I was still (more often?) constantly refilling the circuit to keep the pressure up.

A few weeks later on a Sunday, I needed to remove the rad again, drained more carefully (2 litres-ish), and when replaced and refilled, more boiler issues - no start at all, just during a cold snap of course.

Monday am I called the folks, who said they'd come Tues, so the Monday night (thinking it was my removing the rads that was causing trouble) I drained everything and removed the rads in the two other 1st floor rooms I intend to redecorate this year, and refitted with stopcocks/isolation valves (not sure what they're called, Danfoss, look like 'RLV straight', page 1 here: http://hiti.danfoss.com/PCMPDF/VDQDC402_RLV_pressfit.pdf) so I can remove the rads without needing to drain everything next time round).

Bloke came Tuesday, replaced the pump, and two other in-boiler components (I can find out details, if required), and boiler working OK. For a while... but I still keep needing to refill to keep the pressure up. Pressure can drop from 1.7bar to ~1 within <1 hour


This schematic (fixed-width font best) shows the rads (S=small, L=large/double)

........................./1st floor: 2xL + 5xS
......................./
.(Ground) Boiler, tank --- 1xS+ 3xL......................./ underfloor heating in conservatory (~12m2) added after initial build
........................\.................................................../
..........................\---transfer pump, which feeds/

If you've read this far, thank you.

Observations:
0, I always repressurise cold, to ~1.7 bar
1. Then, when restarting the boiler, bubbles are *immediately* heard, then lessen
2. After repressurising, restarting, and letting HW and rads heat up, there's no gas to bleed in the rads (on ground, or 1st)
3. There are several non-functioning TRVs all around the house
4. In one bedroom where I removed the rad and refitted with 2x 'RLV' valves, there's certainly a leak - above the valve, however. The 'RLV' valves have been shut since I realised that, so the leak above it shouldn't (?) have an effect
5. There's no way (stopcock or equiv) of isolating the conservatory from the main system
6. The general system is not a loop - there are 6 separate flow and return circuits to the various areas of the house a bit like this: http://www.thermotech-underfloorheating.co.uk/images/underfloor_heating_manifold.jpg
7. There is no sign of leakage (walls, ceilings) anywhere that I can see (but I can't see around the underfloor heating in the conservatory)
8. There are a few mildly rust-stained pipes leading from rads I haven't touched

I keep putting water in, bit have no idea why the pressure keeps dropping.

What I'm asking:
1. How can I go about *systematically* tracing the likely sources of the leak(s) I evidently have?
2. Beyond opening, and reclosing with PTFE tape, is there anything more I can do to improve the seals for the rust-stained rads, and those I've dis/re-connected?

I'd be very pleased to hear your thoughts...

With thanks in advance,
Steve

To go from 1.7 to nought in an hour can be as much as 3 litres of water.

So if you can't see any puddles it is going out in one of two places. the pressure relief valve or in the floor.

Find your pressure relief valve outlet and tie a condom to it. repeat your test. No water in condom? start digging. Condom the size of a marrow? get a new pressure relief valve fitted and expansion vessel checked.

Paul Barker said:

Find your pressure relief valve outlet and tie a condom to it. repeat your test.

Click to expand...

Hi Paul,

Thank you for your reply.

The pressure relief valve outlet is the tube dangling into the air from within the boiler, right? Would it be anywhere else?

Only a few drops there from time to time, and certainly not a pint.

Based on the water meter reading (checked for accuracy by filling a 1 litre bottle first) 1->1.7 bar takes ~450ml.

Seems very little given the size of the system (house is ~200m2). Does that sound sane?

Oh dear.

Yes I don't measure it but when I remove the pressure from a system entirely it is between a quater and a 1/2 a bucket of water, then flow stops.

So that is how much you are losing in the time it takes to go from 1.7 bar to nothing.

the pressure relief outlet should not drip at all it should be bone dry.

After that is repaired and the expansion vessel checked you have to see if there is still a problem, and if there is you have to find the pipes and joints and inspect them.

We were collecting a few hundred millilitres of water daily from the pressure relief valve, so the boiler chap came, replaced the pressure relief valve, and the boiler's purring away, and no loss in pressure - so far.

The PRV was clogged up with black gunky stuff (corrosion by-products, I suppose), and looking through the service history, it's only two years since it was last replaced

Thanks for your replies Paul.

Best wishes,
Steve