Help - Multiple Call Outs & No Luck

[SG82]

Dear All,

Would be extremely grateful for any help you could provide:

We recently moved into our new home which is a flat which is 15 years old. Boiler (Potterton Suprima) is in the kitchen and hot water tank, central heating pump and expansion vessel in cupboard.

One night boiler was just not working - called out engineer who said it had developed an air lock and fixed it.

After that noticed pressure had started to drop and needing filling once a week - called a nice gas safe engineer who felt that the AAV was leaking and replaced it. Also noticed pump was not working well and replaced that.

Unfortunately the pressure is still dropping and still needing to top up once a week - original gas safe engineer not contactable and called another guy out who had no idea.

The central heating pump is working fine. Put a bag over the expansion vessel pressure relief pipe and no water there after 24 hours. No obvious leaks from any of the radiators or pipes.

Any suggestions/tips would be much appreciated.

Thanks

S

 

[craig51]

Have you checked all rads( with your hands, have a feel) for any leaks, tops and bottom of them?

Secondly, are you on the ground floor or is there someone below you.

Assuming its not the rads, not the prv as you stated, then it could be a split heat exchanger. I leak is very difficult to detect as normally they only leak when the metal expands, then evaporates away as the burner is on. Usually there is staining on the insulation padds!

Does the pressure drop to 0 if left?

 

[SG82]

Hi Craig,

Thanks for your help,

Rads all get hot - two of them are slightly cooler at the bottom compared to the top.

On 2nd floor - no evidence of pressure drop prior to boiler breaking down first time and no issues from downstairs about watermarks etc.

Apart from looking at the insulation pads - anything else which would tell me its a broken heat exchanger?

Also when boiler first comes on sounds like its filling up with water and this sound stops after 10minutes. Same sound in central heating pump which stops after 10 minutes.

S

 

[misterdubya]

Look up FAQ's on how to re-pressurise an Expansion Vessel - and check the schraeder valve. They often leak air / water if the vessel is shot.

Mr. W.

 

[craig51]

Ok,

When I said check the rads, I meant all the valves on both ends, and also the plugs at the top on the ends. SOmetimes they weep, and its doesnt take much to show on the pressure gauge. This will rule out the rads leaking. But do check with your handes and dont just look.

Also, the suggestion above is good, but if it was a shot expansion vessel, water would be coming out the prv, which you said it isnt. As for it leaking from the schreader valve, and would have expected you to notice a leak under the boiler. Is there any water evident lying under the boiler?

ON a sealed system, the only place for water to go is,

1/Leaky pipe
2/ Leaky joint (valves, plug etc etc)
3/ Out the prv (due to al different faults)
4/ Leaky rad (pin holed)
5/ Bust heat exchanger (hard to tell as per my first post)
6/ SOmetimes, but very rare the local water pressure can drop to quite a low pressure, sometimes not even enough to pressurise a system. If you have a leak in say a cylnder coil, the water can push back into the cylinder that way. But, you would expect to see a ise when the pressure picked up, so doubtfull.

If it was fine before the engineer was there, and he 'cleared an airlock', then something he touched might be causing. Maybe a leaking auto airvent?, maybe the new pump when installed in leaking, or, pipework downstream or upstream of the pump in leaking after being jiggled when installing the pump

What you could do to prove where its leaking, is to turn isolated the flow and return under the boiler. You would then have to keep the boiler off and see if pressure drops. If it does, then its leaking on the sytem, if not, then its leaking on the boiler. But tis may take a while, and you would be cold in the meantime.

 

[Agile]

Hang on Craig! This is a silly Suprima!

There are no isolating valves and the pipes are at the top left !

Clearing the airlock will have removed the little remaining air which was absorbing the expansion. Now there is nothing to stop the pressure rising as it warms up.

OP its a problem with the expansion vessel which needs sorting out first.

After that if any pressure loss still occurs then that can be followed up.

Tony Glazier

 

[craig51]

tis is true!!!! must have been on my rambling mode.

But he did say he put a bag over the prv and nothing came out, so it must be elsewhere.

OP, top it up to 1bar, leave it on heating and watch the gauge. Tell us what it does after 5/10/20 mins.