How do I find a (small) leak from pressurised system

[JImCPN]

I see that there was a post in November that refers to a LARGE leak, but ours is much smaller (needs topping up every ten days to two weeks, perhaps a litre over that period). It has been going on for about six months. The boiler is new since last year; however, to cover all bases, we called the installer out and, predictably, they found no fault. Interestingly, they had no suggestions as to what to do next. Most of the pipework is exposed and there is no sign of leakage anywhere. There is a small amount of piping boxed in and I (rather cleverly I thought, my wife will be SO impressed when I find the leak) invested in a cheap borescope and had a look. As far as I can tell, it is all dry - but I can't see everything and the quality is not brilliant.

It is certainly irritating .... and my wife has nightmares of the house foundations gradually dissolving. My questions are

1) How common is this sort of slow leakage and is it likely to get worse, assuming there is a small leak somewhere?
2) Are there other methods of leak detection? The previous post mentioned a specialist firm, but that sounds pricy - is it? What methods do they use? I just have a feeling that a really expensive borescope used by an expert may do the job ... but where do I get advice from without committing myself to a large invoice?
3) How common is this problem?

Jim

 

[John.g]

He says in post #1 that "Most of the pipework is exposed". It would be interesting to know if the leak was found or not.

 

[Lou]

(Just bumping a few older threads, they will drop off what is new soon)

Check Out Plumbing News!

 

[PRoger]

Not sure if replying to old threads is discouraged, but I'm having to top up my pressure roughly once every six weeks, have had the gas engineer round to look at the boiler and he couldn't find anything and there's no signs of anything on the visible pipes.
Because it's a slow drop, I was thinking leak sealer might be the best option? Is it something I would do myself or should get a plumber round? The boiler is a Worcester Bosch Gr8300iw 30 C if that makes any difference.

 

[Chuck]

Not sure if replying to old threads is discouraged,

I think it's better to start a new thread for a problem about a specific system. I may not be typical, but I don't have the time or patience to figure out which answers refer to which questions.

I was thinking leak sealer might be the best option? Is it something I would do myself or should get a plumber round? The boiler is a Worcester Bosch Gr8300iw 30 C if that makes any difference.

I consider leak sealer to be temporary fix to be used as a last resort, e.g. to buy time before the system is re-piped. The best option is to find the leak.

That said, adding sealant is an easy DIY job. Use a well-known brand, preferably the same one as the inhibitor you have in your system, and read the instructions carefully.

 

[John.g]

Not sure if replying to old threads is discouraged, but I'm having to top up my pressure roughly once every six weeks, have had the gas engineer round to look at the boiler and he couldn't find anything and there's no signs of anything on the visible pipes.
Because it's a slow drop, I was thinking leak sealer might be the best option? Is it something I would do myself or should get a plumber round? The boiler is a Worcester Bosch Gr8300iw 30 C if that makes any difference.

Did your engineer check the age of the EV and also then depressurise the system to check the precharge pressure, if the filling and precharge pressures are the same then any slight leakage will cause a large pressure drop (water side) but the system may only have lost a tiny amount of water.

If, for example, a 8L EV has been charged properly with say precharge/filling pressures of 1.0/1.5bar, then the system will have lost 0.56L in falling to 1.3bar, if precharge/filling pressures of 1.0/1.3bar, then the system will lose 0.66L in falling to 1.1bar.
You will have a fair idea when topping up, if the pressure rises very very fast then probably/possibly pre&filling pressures equal.

What is the pressure drop in those 6 weeks, any idea of the EV capacity?.

 

[PRoger]

Did your engineer check the age of the EV and also then depressurise the system to check the precharge pressure, if the filling and precharge pressures are the same then any slight leakage will cause a large pressure drop (water side) but the system may only have lost a tiny amount of water.

If, for example, a 8L EV has been charged properly with say precharge/filling pressures of 1.0/1.5bar, then the system will have lost 0.56L in falling to 1.3bar, if precharge/filling pressures of 1.0/1.3bar, then the system will lose 0.66L in falling to 1.1bar.
You will have a fair idea when topping up, if the pressure rises very very fast then probably/possibly pre&filling pressures equal.

What is the pressure drop in those 6 weeks, any idea of the EV capacity?.

I'm sorry I don't recall all the details, but the expansion valve has been replaced recently with the justification from the engineer that it might solve our problem. Pressure would usually be going down to something like half a bar before I notice and top it up.



Re: leak sealer, I'm supposing it doesn't make any difference where in the system it's added? Most of our radiators are some sort of "vintage" model so they might be uncommon fittings.