Combi boiler losing pressure.

[iamdaveb]

Hi there,

Im new to posting in this forum, but am having to resort to this as I need further opinions relating to this issue. I am pretty clued up (now!) so hopefully this all makes sense.

Starting approx 6 months back we started to notice that the pressure was dropping on our Worcester Bosch 28CDI boiler (combi). We topped the system up using the filling loop and bled the air out of the rads. Over a few months the pressure was gradually dropping faster and faster to the point that we are now losing virtually 1 bar overnight. This has now been the case for the few month and there is no sign of a leak.

We have had British Gas out using our homecare agreement and have tested all known possibilities.

• There is no water for the pressure release pipe outside
• No damp pipework around the rads or boiler.
• Expansion vessle has been checked and was fine

We have isolated the boiler from the system and this seems to prove that the leak is in the system and not the boiler (eg. Boiler pressure remains at 1bar over 12hrs, but when opening intake values a gush of air enters and the boiler drops pressure)

Our pipework downstairs is buried under a concreate floor, so we have always suspected that the leak was somewhere there. But with nearly 6 months of leak, we thought there would at least be a sign or even smell coming through the laminate floor.

TWIST
I was getting fed up of topping up the CH a week ago and could not be bothered to bleed the rads after topping up. And for some reason the pressure did not drop so fast. Once the pressure dropped back down to zero (took 24+hrs), I topped up again to 1bar without bleeding the rads. The pressure seems to have stablised and has not dropped now in 3 days. Now this has really confused me as everything seems normal again, with the exception of having air in the system. I have checked all the rads and are hot top to bottom, so I'm not sure where the air is. Please someone make sense of this for me.

A few days back we had British Gas out again to quote us for a repipe/repair as our homecare only covers the boiler. Obviously this is a very costly proceedure and I just need some ideas of what we should do. If there is a leak, then we still have no idea where it is and this would require thermal imaging to locate (costly). Should we leave the system with air in and just assume that all is ok?

Your thoughts and suggestion would be a much need help

thanks in advance

 

[Billsaint]

I had the same /similar problem recently.The house was 40 years old and the pipes were all in the concrete. I found the bathroom floor had recently been retiled.

I took up the carpets and eventually noticed slight mold mark on part of the skirting .

I took the skirting off and found it was very wet and rotten. I eventually got a small kango and broke up the concrete to find an old solder joint had perished. Apparently its quite common for these to go after a number vof years as the acid in the flux reacts with the acidity in the concrete.

I replaced part of the pipe, and a new fitting I also lagged the pipe.

Nowadays all pipes placed under concrete should be in palstic lined piping to stop this happening again.

I finished up selling them one of my leak detectors . Look at my website Home and you will see them.

Good Luck

Bill

 

[Transcoman]

Products look good Bill, but i'd do something about the website appearance; for example, blue text on a blue background doesn't work very well.

 

[Billsaint]

Thanks.

I will look again at the colours ,maybe they need some changes.

How would you suggest I best promote my products to the pluming trade,.. maybe on this website.But I dont know how to do it.

Bill

 

[Transcoman]

Thanks.

I will look again at the colours ,maybe they need some changes.

How would you suggest I best promote my products to the pluming trade,.. maybe on this website.But I dont know how to do it.

Bill

Bill,

For my sins l used to do a lot of website building during the quieter summer months, i'd be happy to give you some free advice - if you want it, please send me your email address by Private Message on this board and i'll be pleased to help. I'll add a link on our website to your site later this evening.

Steve.

 

[Billsaint]

Thanks steve

my email is [email protected]

 

[traineedrip]

The reason its behaving better with air in the rads is the air is soaking up pressure in the same way the air in the expansion vessel does it. Less pressure, less of a leak.

definately no water dripping out of the outside copper pipe?

Can you watch the pressure on the boiler? what does it rise to while working?

 

[iamdaveb]

traineedrip:

I have tried to observe the pressure whilst the boiler is in action, but it doesn't seem to move, even after 10mins of constant heating. The PRV piping is dry (have had a container under it for over 2 weeks now and nothing).

The only other thing I can add is the condenstation pipe seems to be dripping whilst the heating is active. I'm sure I read that it was ment to collect approx 150ml before emptying. I originally wrote this theroy off as we had already isolated the pressure dropping to the system and not the boiler.

cheers everyone else for making this a website design discussion . Just kidding really, at least I know ppl are looking at this post.

 

[gedtodd]

doe's the pressure drop when their is a call for hot water?

 

[iamdaveb]

gedtodd:


I have witnessed a very slight drop in pressure when the boiler is called on for the CH, but this isn't always obvious. As stated before, the pressure never increases as you would expect.

 

[gedtodd]

HI Dave,
before bg turn up have you checked/tested as recommended with other related issues on the bottom of this page?

 

[bbcmjr]

Hi Guys

I read with interest your thread. My boiler too is loosing pressure but I did notice that the external pipe is dripping water. Any advice for a remedy please ?

cheers Mike

Hi again

forgot to mention the other problem I am having. Sometimes the boile goes out and will not ignight when I open the hot water tap. I have to manually start the boiler and it takes a while fo hot water to come through. Any ideas please ?

cheers Mike

 

[Billy Bob Bob]

expansion vessel flat or faulty,filling loop passing,over pressuring,internal fault ie-plate heat exchanger or colirifier [if its quite old] also whatever the cause you will need a prv

does the second fault occur with low pressure?

 

[bbcmjr]

Yes - I did notice dripping even when the pressure was low, but not as much.

cheers for the reply

Mike

 

[Billy Bob Bob]

simple check first disconnect the filling loop see if its passing,looks like second fault is caused by the first

 

[bbcmjr]

Thanks I will give it a go.

cheers Mike