Looking for a leak in my sealed HW system

I've read the 'Sealed System' FAQ but really need some more specific advice about why my boiler may be loosing pressure and how best to find the cause.

Here's the score:

-Vokera 20SE system boiler fitted on ground floor. Sealed system.

-2 storey semi, recently extended, boiler recommissioned September

2003.

-before extension: -boiler running 10 rads and conventional copper cylinder -boiler needed represurising every 4-5 months

-after extension: -boiler running 14 rads (10 new, 4 existing) and megaflow cylinder -boiler needs repressurising every 7 to 10 days! -no visible signs of a leak

-Boiler has been checked twice recently by Vokera engineer; no visble leaks or faults found; suggested getting plumbers to 'air test' HW plumbing to find leak.

-I typically repressurise cold system to 1.5 bar. Pressure never exceeds 2 bar when hot. No sign of pressure relief valve operating.

The plumbers who did the new plumbing and recommissioned the boiler are coming to drain and air-test soon. I'm hoping that this will help ID the leak. BUT over the past week I've noticed that the presure is falling less quickly than it was before.

Questions I'd appreciate help with:

  1. Does this sound like a leak? If not, what could it be? Is it typical? Will it fix itself?
  2. Last time I adding water (filling loop beside boiler), I didn't bleed the rads, like I normally do. So far the pressure has fallen more slowly. Is this a sign things are sorting themselves out or could there be air in the rads which is somehow keeping the overall pressure up?
  3. Is there a good approach to doing this air test? (I'd like to know whether the plumbers are doing sensible things!) I intend being their to oversee things.
  4. Should they add inhibitor when they refill? If so, what type is best.

Thanks in advance,

Dave G

Reply to
David Green
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This is a leak, but a fairly slow one. Pressure relief valves are prime candidates, especially if opened during the plumbing.

Not a serious one, but it is. It may resolve itself.

I think that this is coincidence. Try taking the caps off of the radiator valves and looking underneath. Seeping from them is not unusual. The water can be so little that the heat will evaporat the water before you see it. This could even have happened with the existing radiators.

Definitely. I've always used Fernox products (have done for over 20 years) and results are consistently good. You can either introduce as a liquid, or for a sealed system they do a gel version which can be injected with a mastic gun. Sentinel products also have a good reputation. I wouldn't use cheap, own brand products from DIY stores etc. simply because there is no information on them. For the sake of a few pounds, this is a good insurance policy.

Obviously you need to address the leak issue first.

.andy

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Reply to
Andy Hall

The only thing I would add is that since the boiler is out of guarantee there is no harm in using a product like Fernox LS-I (which look and smells like PVA glue) this will halp to seal the very very small leak you have and is a lot less invasive than trying to hunt the needle in a hay stack.

I beleive you can also get an aromatic substance to put in the primary circuit then your nose can tell you where the leak is.

Reply to
Ed Sirett

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