Leak below boiler after PHE swap

[Fez111]

(Main Combi 30 Eco)

Hi All,
I wonder if you can help.

I changed a clogged plate heat exchanger on my boiler a couple of months ago. All seemed to go well and hot water was consistent again.
Since then however, I have had a leak from the bottom of the boiler. Didn't notice it for couple weeks until one day came home to see it leaked from worktop to floor. Initially was small but has now grown more significant (and emptying the small bowl from under boiler a few times a day)

Are there certain steps to follow as process of elimination to identify the source of the leak?

If it's relevant, I was only able to change one of the plastic washers in the pipes that connect to the PHE as couldn't get the other out. I also didn't grease/silicone these connections as wasn't clear I had to.
Also if relevant, the water appears to be coming from directly above the hot water out pipe below the boiler.

Thanks in advance for your help guys.

 

[ianmcd]

if you are not having to keep re-pressurising the boiler then the leak is on the DHW mains side, not sure what you mean about plastic washers, as this setup uses rubber type seals called lip seals, you need 4 of them and you should always replace them whenever you remove the PHE, I have attached a link so you can see what the look like , I always use a small smear of silicon grease on each face of the lip seal.

https://www.ebay.co.uk/sch/i.html?_...in+combi+30+eco+plate+heat+exchanger&_sacat=0

https://www.ebay.co.uk/itm/4-X-MAIN...695424?hash=item362a1bbf00:g:feoAAOSwMfhaYJOC

 

[Fez111]

Thanks for the quick and detailed reply Ian.
I realise I was using the wrong terminology and it is the lip seals that I was referring to. Having just opened the boiler, (though I can't be 100% because it's concealed behind pipework), it may be one of these lip seals leaking, possibly the one I was unable to change. I will try to find a full set on their own online, and replace and regrease.

As for the re-pressurising. I noticed that in the days when we had the heating on it would reduce and would need to re-pressurise near daily, but hasn't needed to be since the last week when heating hasn't been on.

I tried to reproduce the problem just now by switching on heating and the pressure went up from 1.5 into the red range. (still sitting there now, having just turned the heating off). Also appears to be a leak outside from overflow pipe. I'm guessing this indicates a different problem? Maybe caused by overfilling when the pressure kept dropping.

Thanks

 

[ianmcd]

when you drained the boiler to change the PHE did you use the Pressure releif valve to do so ? if you did you will have to change that to, I added a link for the lip seals in my last post, they are called lip seals as you will see why when you see a new one , it looks like a single lip but once installed the face becomes flat hence why you shouldnt reuse them

 

[Only me]

The issue with the increase in pressure when the heating is on will be related to the expansion vessel. It’s either burst, needs recharged or the connecting pipe or flex is choked with grit.

 

[gasbusters]

The expansion vessel needs recharging if pressure is going into the red. You need to get a registered gas safe engineer to come and service the boiler. Main boilers are notorious for expansion vessels to loose their charge pretty quickly. Id say 90% of those I attend for gas safety inspections will need a service as the presdure goes onto red when heatings on.

In regards to the leak, as mentioned above change the washers and use silicone grease, but if your getting it serviced you may as well get the engineer to sort the leak out as well.