Boiler losing pressure

[Ben2411]

First time post so go easy, ive had an ongoing issue with my boiler loosing pressure, ive had boiker chexked over and they suggest its a fault with pipework, ive checked for ceiling staining and around all radiators however all dry and no obvious signs, weve tried fernox f4 leak sealer still to no avail, boiler pressure will drop every 3-4 days max depending on use, has even needed topping up after 24hrs, we are almost atbthe point of paying a leak detection company to come and check the system over, im concerned they may find nothing, so hoping yiubguys may have some tips i could try, i am an electrician by trade so have a good understanding just wodnering if i may of missed anything, so any advice on how you guys would approach this would be much appreciated

 

[John.g]

Hi Ben,
Is it a gas or oil fired boiler?
is the expansion vessel internal in the boiler or externally mounted.?
Any sign of water leak from the PRV (safety valve), this should'nt lift unless the boiler pressure reaches 3bar. (but could be leaking at any pressure).

 

[Ben2411]

Its a gas fired ideal logic+ 35kw, expanison tank is internal to boiler and has been checked, no water came from the schrader valve, ive become abit paranoid to be honest and constantly check the PRV pipe outside and its alwsys dry

 

[Ben2411]

I think on looking inside boiler there has been leaks around the hest exchanger but no new i think that was historic before we moved in

 

[John.g]

Shouldn't really be looking inside boiler casing unless gas approved, if the EV has been precharged to 1bar and you have filled to 1.5 bar then you are losing ~ 2 litrs of water in a short time which points to a leak.
You could break the condensate pipe and see if its dripping/leaking with boiler shut down. After switching off/isolating you could fill the boiler to say 2bar when cold then shut the boiler flow and return valves and see if the pressure falls over a few hours, if so, then probably boiler Hx problem if valves are holding tight.

 

[EvilDrPorkChop]

Heat exchanger will be leaking back down the condensate pipe. Common problem on these, is boiler about 6/7 years old?

 

[Ben2411]

Id expect around that kind of age yes, we had the siphon changed a few years back as it had cracked another common issue i believe, can you tell me how To best check if this is happening presumbaly wster down condensate when boiler off

 

[ShaunCorbs]

Turn the boiler iso valves off either side black 22mm leave 24 hours with no heating or hot water on eg turn boiler off

 

[EvilDrPorkChop]

As Shaun says above......

 

[Ben2411]

How long should the boiler be off before isolating? Presumbably if just been hesting the pressure will drop, is it worth disconnecting the condensate under the boiler over night

 

[ShaunCorbs]

Same time and no

 

[Ben2411]

Okay i will try that tonight, how much pressure shkuld ot loose when closing the valves after having been hot just to tey and eliminate a false droo

 

[ShaunCorbs]

Shouldn’t drop below 1 if it’s around 2.2 now

 

[Ben2411]

Thats great thanks, should i make sure its at 1-1.2 before having heating on to know that its up To pressure etc

 

[John.g]

I would think that if it's leaking down through the condensate pipe that it doesn't matter whether boiler and system are isolated from each other or not.