Central Heating Boiler Losing Pressure

[sickasaparrot]

I hope someone can help, we are at our wit's end. We have been losing pressure in our central heating boiler for some weeks now, have had the Gas Board out eight times to look at it and we're no further forward.
They've fitted new valves and a new expansion vessel, but it has made no difference. We are having to top it up at least twice a day, as it goes right down to zero. We fastened a bag on the pipe that goes outside and no water is coming from there. We've checked the radiator valves and there are no obvious leaks anywhere.
About ten days ago the Gas Board engineer said he thought we may have a leak in the pipes in the cement floor and used Fernox, this made no difference until a few days ago when the pressure stayed up for a couple of days, and we thought we'd solved the problem. However, the pressure is falling again. If there is a leak in a pipe in the floor then why did the pressure suddenly stay up for a short period? How on earth do we find a leak in a cement floor?
Any suggestions would be appreciated.

 

[ChrisR]

How on earth do we find a leak in a cement floor?

One, non facetious answer is that you don't. You replace all the pipes , running them on the surface. If you have one leak now, you are very likely to get more.
It/they are likely to be where the pipes come up through the screed, so it can be practical to inspect the lot, with digging at each one.

Personally I'd try another bottle of leak sealer first.

There are firms which WILL find your leaks by
1) Thermal imaging
2) acoustics - listen carefully.
3) gas diffusion

One I have details of somewhere charge a flat £250.

methods 1 and 2 you can have a go at yourself. (infra red thermometers start at £25)

 

[Slugbabydotcom]

Sussed one out like this up in Jarrow a few weeks ago.

I looked all over doing me Sherlock bit and looking for clues of dampness and discovered that there where strange things going on with the laminated floor namely squidginess and swelling.
I also used my ears and figured that when the pressure was up there was a rushing noise in the downstairs bathroom.
It was a downstairs flat and the rear 2 rooms [bathroom and kitchen] were concrete, the rest was timber. Luckily I was able to cap off the flow and return to the 2 rads at the rear that were fed through the concrete floor.
That leak could be anywhere under that concrete floor and I ain't digging it up. They will get re-piped sooner or later but for now at least the tenant has half a warm flat.

 

[scatmanjohn]

What boiler have you got.

 

[sickasaparrot]

What boiler have you got.

We have a Potterton Ultra 2.

 

[sickasaparrot]

The Gas Board engineer called again today as the boiler was still losing pressure, and we were still topping it up twice a day.
He insisted there was a leak in the pipework in the concrete floor, (he even offered to get us a quote for new pipework). When we insisted on evidence of faulty pipework he once again inspected the boiler, but said he could find no fault.
However, the problem seems to have gone away. We believe that he would open a valve to reduce pressure when injecting sealant at his last visit. If he inadvertently left this valve open would it result in a constant loss of pressure?

 

[baxpoti]

Topping up twice a day would show up as a leak - somewhere!

If your convinced its not the pipework, eliminate the pipework by isolating the boiler (WHEN NOT IN USE) (and yes I know its cold), at the flow and return valves underneath the boiler (which will leak when you open them again) If the guage drops after the normal drop time the boiler must be leaking/losing pressure, if the pressure guage (on the boiler) hasn't dropped , then the fault is more than likely in the pipework / rads. To prove this when you open the valves the pressure now drops.



Clear as mud

 

[sickasaparrot]

Thanks for your replies. We're more or less resigned to the fact that we're going to have to have the place repiped, just the job for the middle of winter.
Can I ask one last question. The leak must be in the concrete floor, there's no sign of damp anywhere. Why does the rate that the pressure drops vary so much? We've topped it up to 1 when we've gone to bed and it's been down to zero the next morning, yet the gas engineer topped it up to 1 yesterday afternoon, and it's hardly dropped at all?

 

[oilman]

When the heating is on, can you feel that warm water has moved into the expansion vessel? The connecting pipe could be blocked.

 

[sickasaparrot]

Thanks for your reply Oilman. We're not losing any water from the pressure relief pipe, so thought this meant the expansion vessel was OK.

 

[sickasaparrot]

The saga continues. On Sunday the pressure didn't drop at all, on Monday and yesterday we had to top up the water three times as the pressure had fallen to zero on on each occasion, yet today it hasn't fallen at all. If there is a leak in the pipes in the concrete floor why is there such a variation? There is no water coming from the pressure relief pipe
outside.

 

[stevedo]

We had a similar scenario to yours just over a year ago. We initially had a leak which was traced to a broken pipe in the concrete floor. This was dug up and repaired (easy to find due to damaged/water stained maple flooring). After about 6 months the system started to lose pressure again. I tried leak sealer which seemed to help a bit with varying rates of pressure loss noted. Worst case was 1 bar to 0 in about 6 hours. Given that we were topping up on a regular basis it was obvious that the leak must be in the concrete floor, otherwise something would be very wet.

The only course of action for a long term solution was to completely repipe above concrete floor level. We were fortunate in that we have a local plumber who did a great job of ensuring that all pipework was hidden without any unsightly boxing. No pressure loss since

As a matter of interest how old is the house? Ours is 35 years old and the pipes we've seen in the floor were not protected from the concrete and had just come to the end of their serviceable life.

 

[Agile]

The Potty Ultra 2 was often used in conjunction with a thermal store. ( I do hope Water Systems does not see this as it reactivates him. )

Could the store be leaking system water somehow?

Have you isolated the boiler from the system ???

If I recall correctly the boiler has a built in diverter valve to switch between heating the rads or the thermal store.

If I am correct have you tried tieing up the ball valve and monitoring the level in the store feed tank?

Tony

 

[Softus]

Ours is 35 years old and the pipes we've seen in the floor were not protected from the concrete and had just come to the end of their serviceable life.

Interesting observation - I've seen someone else claim that copper lasts for 100s of years.

 

[sickasaparrot]

Hi Stevedo, thanks for your reply. As you say, it's probably bits of sealer bunging up the hole/holes temporarily. The pressure has fallen from 1 to 0 in about three hours on occasions.
Our bungalow is about 26 years old, and the Gas Board Engineer said the lime in the concrete would be corroding the copper pipes as they wouldn't be in plastic.
We're going to do the same as you and have a re-pipe done, it's the only way we're going to have peace of mind as if we find one leak and repair it we'll just be waiting for the next one to appear.
It's a sealed system Agile, so we don't have a store feed tank. Thanks for your reply.