Boiler leak, engineer can't find

[nigelthorn]

Hi, just wanting to sense check if the service I've got here has been reasonable or not. Same company throughout.

Jan 2025 - serviced boiler, advised likely ~4yrs left on it but could extend to 7-8yrs if powerflush the system as was real grotty
Sep 2025 - had problems with cold shower which we felt probably pressure related got it looked at and power flush done, been fine since
Nov 2025 - in last few weeks noticed a leak from bottom of boiler (no problem with heating/shower etc, only noticed because stuff underneath it was getting wet).
They came to look at it, said pressure was low and they didn't know how our heating was still working. Couldn't work out where leak was coming from even with heating on full. Suggested trying replacing automatic air vent as this is corroded (but not mentioned at service so ?happened since) could be intermittently splashing and causing a leak, but couldn't do that in same visit, would need to book in again and request another visit with the part. Then got an email saying we recommend you replace your boiler because replacing air vent (which we're not even sure is the problem?) will be expensive. Visit was >£200 to tell us what could be a possible problem but not fix it (is this normal?)

Since the engineer came the leak is now worse and happening continuously to the point that I think I can see it may be coming from the condensate pipe (though this is without taking the front off).
Is it reasonable to be asking them to come back to re-look at the same problem because whatever they've done (I thought nothing just repressurised/filled up) has made it worse and not fixed it? Are we just going to get charged another £200??

 

[Johntheo5]

If you are not topping up the boiler regularly then well more than likely that its a condensate leak, probably from the drain pipe or maybe its blocked, can you see where the condensate drains off?, does the leakage stop when the boiler is off/.

 

[nigelthorn]

Yes the leak only seems to happen when the boiler's on. The guy mentioned checking the outside pipe while he was here and said it was lagged so shouldn't freeze but do they just get blocked up with other stuff sometimes?

 

[Harry Bloomfield]

Yes the leak only seems to happen when the boiler's on. The guy mentioned checking the outside pipe while he was here and said it was lagged so shouldn't freeze but do they just get blocked up with other stuff sometimes?

Yes, they do. A simple job, to just check yourself. Pour water in, and it should quickly flow out at the other end.