Vaillant Combi continuously losing pressure

[zain]

Hi people

wondering if you could help diagnose my problem.

I have a Vailliant Eco Max Combi boiler, all was well until 2 weeks ago when I decided to change the radiator as my wife thought it was old and ugly
Whilst removing the rad I developed a small leak from the old thermostat. I called a plumber friend of mine who informed me the thermostat needed replacing, he then went on to shut of the central heating system but we still had hot water.
We had no heating for a few days until he returned and fitted new fittings on the leaking pipe and turned the heating back on.

This left me with heating and hot water but a missing rad which was supposed to be re-fitted from the plumber in a 'couple of days'

The next day I developed a fault with the boiler. F.25 no pressure. I topped it back up to 1.5 and a within a few hours it had drained again.

Ok, the house is covered with British Gas. Called them out and they came the next day.
The engineer re-filled the expansion tank? with air. Eventually he had a good look around and came to the conclusion that there is Oxygen in the water and need to top it up when the rad is re-fitted.

Here are the things I've checked my self; external overflow pipe, bled all the rads and checked for leaks (even under the floor)

My Radiator is being fitted Saturday morning.

I'd appreciate any help in diagnosing this problem as I'm not entirely convinced the oxygen in the water would lose 1.5 bar within a couple of hours.

Thanks for listening

 

[kevplumb]

of course there is oxygen in the water h2O

you have a leak

why was the ex vessel recharged

 

[Agile]

You seem to have been relying on a "plumber" who seems rather less than ideal and certainly not very speedy!

It seems he was unable to realise the expansion vessel was discharged but then perhaps he is only a plumber and not a boiler engineer.

Wait until the new rad is fitted and keep the pressure topped up to 1.5 cold and see what it does over a few days.

Tony

 

[kevplumb]

Ok, the house is covered with British Gas. Called them out and they came the next day.
The engineer re-filled the expansion tank? with air. Eventually he had a good look around and came to the conclusion that there is Oxygen in the water and need to top it up when the rad is re-fitted.

get them back

 

[zain]

apparently according the BG engineer this is common problem if the rads are not re-filled with sentinel inhibitor.

The original 'plumber' is in-fact a Corgi gas engineer and obviously to busy to return . The chap coming on Saturday is just a regular plumber.

Any more suggestions? guess it's not a common problem then

roll on Saturday.....

 

[b16kvv]

The only way your losing pressure that quickly is if you have a water leak due to the movement in the pipework due to trying to replace the radiator or your losing it out the PRV which can be caused by 3 things. 1. PRV leaking. 2. Expansion vessel needs recharged or replaced. 3. Heat exchanger has pinhole in it and needs replaced.

I would wait and get the rad fitted then refill and see how you get on and ask BG to come back out if problem persists as the whole oxygen causing pressure loss doesnt fly with me at all!

Kev

 

[zain]

The only way your losing pressure that quickly is if you have a water leak due to the movement in the pipework due to trying to replace the radiator or your losing it out the PRV which can be caused by 3 things. 1. PRV leaking. 2. Expansion vessel needs recharged or replaced. 3. Heat exchanger has pinhole in it and needs replaced.

I would wait and get the rad fitted then refill and see how you get on and ask BG to come back out if problem persists as the whole oxygen causing pressure loss doesnt fly with me at all!

Kev

And here's me thinking all the knowledgeable professional were out at work

Thanks for the informative reply.

I'll be sure to post the out come of this scenario for future reference.

Z

 

[gblades]

Ok first what does the pressure go up to when the central heating is on?

The expansion cylinder is filled with air so that as the water increates in temperature the air can be compressed otherwise the pressure will go very high and could cause problems. The PRV is designed to vent water outside if the pressure does increase too far. The problem with a PRV is that if it does vent once and is quite old it can often not reseal itself so contiinues to dribble water.

So check the output of the PRV (often a pipe going outside) and see if the end is wet and also see what pressure the system reaches when hot.
If its dry and not reaching near 3 bar then it sounds like you might have broken a solder joint around a pipe fitting somewhere while removing the radiator.

 

[zain]

Up-date

it's getting worse, losing pressure pretty much instantly.

Filled it up this morning, ran the hot tap and I could literally hear hissing like loss of air sound coming from the boiler.

What's the brass air valve thingy? Could be that, no

Thanks

 

[kevplumb]

if you are losing pressure that fast you deffo have a leak

does it hold if you don't run the hot water

 

[zain]

if you are losing pressure that fast you deffo have a leak

does it hold if you don't run the hot water

no, still loses pressure while idle.

I did notice it took about 30 to 40 seconds filling to reach 1.5 bar before the BG engineer fiddled with it, and now fills up less than 10.

Hissing sound occurs when the boiler is produces hot water.

I'm pretty convinced it's not a leak, serached every where for water and still after 2 weeks all dry - no sighn of water. Also, the state it's in now should be pi**ing out!

Thanks

 

[kevplumb]

Also, the state it's in now should be pi**ing out!

well its going somewhere

and if its dropping that fast it shouldnt be to hard to spot

 

[Agile]

Have you checked the pressure relief valve vent?

Usually outside behind boiler.

It sounds as if the BG man DEpressurised the expansion vessel !

Fill system to 1.5 Bar cold and then run heating and watch the pressure. I am expecting it to go up to 3 Bar and the vent to discharge.

Are both boiler isolating valves both closed?

Tony

 

[zain]

Well it seems everyone was correct with their initial guess.

Just spotted a leak underneath the suspended ceiling in our business down stairs.

All though it's not coming from where I removed the radiator, a join must have came lose further down the piping. Just called the plumber out

Going have to get at it from underneath, at least it will be covered by the suspended ceiling. As the kitchen has newly laid marble tiles (£20 a tile ) then 4' ply, then the floor boards, then the insulation, then the plasterboard ceiling (which will soon be in a mess) and finally the suspended ceiling.

I'll add closure to this after repairs have been carried out.

All because the wife thought the old radiator looked ugly

Thanks to those who have contributed

 

[Agile]

Often you can claim the consequential damage from a leak from insurance!

Tony