possable leaking pipes

[dreaddan]

Hi,
Our Hallstead quatro seems to be losing pressure
I've had BG out twice now who have re pressurised the expansion vessel however it's still dropping a bit.

So I thought id have a quick look at a few pipes that I can get at relatively easily.

And found these pipes and wondered if they look like there leaking or if its just because there under a bathroom (well shower/toilet).
Pics are quite big so I've linked them..
http://www.dread.eu.org/thedump/IMG_5780.JPG
http://www.dread.eu.org/thedump/IMG_5784.JPG

Thanks
Dan[/list]

 

[tommyl18]

that green is just flux that hasnt been cleaned off you need to get that off with some wirewool as it will corrode your pipes

 

[dreaddan]

Thanks.
I guess i better start pulling more boards

Is there a easy way to know if the expantion vessale is split rather than me having to pull all the bords up?

Thanks
Dan

 

[tommyl18]

did you say british gas have been out twice to refill it i would have thought they would have noticed something if it was the boiler

 

[dreaddan]

Only the 1st time I can say for sure that they repressurised the system - as he drained some water off first.
The second guy says he went though the same procedures so i cannot be sure what he did. his thuoghts were more that that the safty valve might have gone.

Thanks
Dan

 

[dreaddan]

Ive remmbered the 2nd guy said it's possable theres a small tear in the pressure vessle and to call him on monday letting him know howmuch pressure has dropped.

Im just trying to speed things up by doing what i can to isolate the issues so i dont have to take any more time off.

Ive found another join that looks suspect
http://www.dread.eu.org/thedump/IMG_5790.JPG
http://www.dread.eu.org/thedump/IMG_5798.JPG

Otherwise the CH pipes at the boiler have what look isolation values on them if i shut the CH off and repressureise the system that should show if it's the Boiler or pipes should it not?

http://www.dread.eu.org/thedump/IMAG0429.jpg
edit added better pic:
http://www.dread.eu.org/thedump/IMG_5799.JPG
Dan

 

[twgas]

Have you checked the copper discharge pipe that goes outside, if in doubt tie a plastic bag over it and check tomorrow morning.

 

[dreaddan]

Yep nothing has come out - I worked from home on friday where i could see the pipe nothing..
But i might stick one on anyways.
Cheers
Dan

 

[MANDATE]

when pressurizing the expansion vessel with air the diaphagm pushes the water back. Now if there is no easy outlet for the surplus water or high resistance, it's easy to be misled. There is more to it than upping the air pressure to 0.8 bar. The expansion vessel must be full with air and not partially filled with water.
If partially filled with water, there is less 'air' volume which would mean a higher than designed pressure increase.
Also it could be the air valve on the vessel is leaking slightly. This would mean the 'air' volume would reduce, especially when the water pressure increases when expansion takes place. It would not take that long before the pressure would open the PRV, then pressure would drop, then you increase it and start the whole sequence again.

 

[dreaddan]

Right so the 2nd guy coulnt have properly checked the pressure without draining some water off?

Out of intrest if there is water getting into the vessle where does the air go?


Thanks
Dan

 

[dextrous]

often out of the valve itself (it's the same design as a tyre valve - can't remember proper name )

 

[MANDATE]

if there is water getting into the vessel where does the air go?

Easier to understand with example. System holds 50 litres of water which when heated for CH expands to 54 litres.
Expansion vessel is 8 litres. The vessel is 'air' charged to 0.8 bar so basically there is no water in the vessel because the diaphragm keeps it out.
As expansion takes place, water begins to push on diaphragm and enters the ex vessel. Eventually the 8 litres of air gets compressed to 4 litres and the air pressure increases. The water and air are held in equilibrum so the water pressure is basically the same as the air press.
Just imagine if the vessel was already half full with water and there is only 4 litres of air space for you to put 4 litres of water. The air would be compressed and pressure would rise at a faster rate and PRV would open at 3bar. The whole operation is based on the fact that 'air' can be compressed and 'water' can't. (well not quite true)

Now if you have a ruptured diaphragm, then water will pass across to the 'air' side and reduce the volume, giving high rise in pressure as above and open the PRV at 3bar.
3 days ago I witnessed BG engineer recharge a vessel, Two attempts and the pressure rise was too much and too fast.
Third attempt with flow and return valves closed and PRV open give a slower rate of increase from 1bar to 2bar

 

[dreaddan]

Right with you - so in my case the pressure is slowly reducing 1.5bar - 1bar in 2 days when cold and now only getting to 2bar when hot is less likely to be the vessel.


Thanks

 

[MANDATE]

If the pressure reduces to less than it was set at and there is a need to keep topping it up, you need to know where the excess water is going.

Could it be a leak in the heating system?
You could put the pressure up to 2bar while cold then close the flow and return valves and leave overnight. If the pressure holds, then leak must in the heating pipes /radiators. If pressure still drops then it must be boiler and not heating pipes/rads

Or is it going into the expansion vessel bit by bit, until there is insufficient room in the vessel to take the excess volume and then force some out through the PRV.
The expansion vessel is charged with air and like car tyres will gradually lose pressure, so easiest and cheapest is to replace the scheder valve.
Also when you take the old valve out, you will know if the diaphragm is ruptured, because water will also escape from the valve oriface

Also it is understood that PRVs don't always make a good seal once they have opened, so could the PRV be the source of a leak even when in closed position

 

[MANDATE]

What I omitted to say was that the rise in pressure when using the heating should be about 1bar. say from 1bar rising to 2bar, or 1.5bar rising to 2.5bar. When the range exceeds this, it is a clear indication of expansion vessel problem. Also when PRV opens due to reaching 3bar is also a expansion vessel problem unless of course the cols pressure was set too high (ie 2bar rising to 3bar)