Glow Worm 30 Ci losing pressure, slowly

[snipa]

Hello everyone,

My first post!
I've been reading on the forums for 3 weeks, since my girlfriend and I bought our first house, but with all the wealth of information on here, I've not needed to post before as many of my questions have already been answered.

However, as stated in the subject heading, our Glow Worm 30 Ci combi boiler has started to lose pressure.
When we got the house, the pressure read 1.4-1.6 bar for two weeks, but on screwing in some floor boards last Sunday, I foolishly hit into a central heating water pipe. The plumber came round and for £45 replaced a small section of pipe and an elbow. He re-pressurised the system to 1.0 bar, checked his work didn't leak and went off but told us to keep an eye on the pressure.

After letting it settle down, I got the pressure back up to around 1.4-1.6 again. Having looked yesterday morning, it had crept down to 1.1 bar and this morning was reading 1.0 bar.

IS the boiler just regulating itself down to the normal 1.0 bar, or is there something wrong somewhere?
Would a tiny leak be a likely cause of dropping around 0.1 bar a day?
Would the plumbers replacement joint be the first place to look, if so, or have I even more foolishly screwed into another section of pipe?
D'oh - we had all the carpets fitted yesterday!

After doing some searching, I found this thread:
//www.diynot.com/forums/viewtopic.php?p=293565

Gasman1015 suggested "Determine whether its a system leak or boiler by isolating flow and return
valves below boiler, while the boiler is off, leave for two hours."

Is this a good way to check for system leaks, and if so, how do I do it?

ANY help greatly appreciated - and please keep the technical jargon as simple as possible!

 

[bobthebender]

It could be air in the system still from when he repaired.
Why don't you shut the boiler off at the power and pressurise to 2bar for an hour or so
You will soon find any leaks if you have any ?

 

[snipa]

Thanks for the quick reply.
After re-pressurising the system, I went round and bled all the radiators, starting with the one furthest from the boiler.
Shouldn't this disperse any air from the system?

So, crank the pressure up to 2 bar, then switch the system off is a plan?
I'll see if the gf minds her new carpets getting potentially wet for an hour or so
Gotta be worth a go!

 

[snipa]

Hmm, after slowly descending down to 0.9 bar, it proceeded to stay here for 6 days, which led me to think it was just the re-filling of the whole system.
On Monday, the boiler suddenly dropped further to 0.7 bar though.

After 2 weeks there's still no sign of a leak so what else could it be? Pressure release valve leaking?

EDIT: Just to add, the safety discharge used to leak quite badly until the last service. Since it only drips very occasionally, and I wouldn't have thought 1 bar of pressure equated water has dripped out.

 

[sturharv]

Sounds like you may have damaged another pipe without realising?? Even with a few drips a small system could easily lose 0.1 bar a day, There may be a small leak in the boiler after the repair work

 

[nickso]

Hmm, after slowly descending down to 0.9 bar, it proceeded to stay here for 6 days, which led me to think it was just the re-filling of the whole system.
On Monday, the boiler suddenly dropped further to 0.7 bar though.

After 2 weeks there's still no sign of a leak so what else could it be? Pressure release valve leaking?

EDIT: Just to add, the safety discharge used to leak quite badly until the last service. Since it only drips very occasionally, and I wouldn't have thought 1 bar of pressure equated water has dripped out.

if the prv is leaking at all then get it replaced.

you dont need a great deal of water to escape to lose 1 bar of pressure.

your other option, if the prv isnt the cause, is to isolate the boiler from the system and see if it still drops pressure. if not you know its the system thats leaking somewhere.

 

[undercover]

Fill up to 2 bar and then isolate your boiler from the system. Isolation valves hopefully under the boiler. Use large flat screwdriver and turn them off.

Wait a few hours or so and monitor the pressure. If it stays still then leak on the system. Check new repair -whos to say that isnt leaking!. Otherwise you may also have nailed through elsewhere. Or it may be just a large amount of air still in the system after repair and refill.

If pressure goes down with valves isolated then think boiler. PRV should be replaced (even though its been serviced. May also need expansion vessel recharging and expansion vessel tube may be blocked??

 

[snipa]

Thanks for all the advice guys. I will crank the pressure up to 2 bar and monitor, but at the rate the pressure drops, it takes some considerable time to show any drop.
From 1.5 - 1.4 took 24 hours, but with a bit more pressure, maybe it will be quicker! I'll also take another look at the safety discharge leak....

If it was only as easy to find me a decent plumber!

 

[gas4you]

If you can, also check any auto air vents on the system or in the boiler as these can sometimes stick open letting drips or a trickle of water out.