Nearly new Keston combi boiler flue coughing/ejecting hot water & steam

[Mark Gordon-James]

Hi everyone

I would be grateful for advice about possible causes of excessive quantities of water being ejected from my flue. When the boiler switches on in the morning, the flue exit from my apartment block generates a lot of steam and then coughs up glass-amounts of water, falling on the pavement below.

The flue exit is connected to my boiler via an 8m or thereabouts flue/pipe inside my lowered ceiling of my flat - the flue probably has not the appropriate gradient, as it is almost horizontal.

The exit of the flue has an S-type of joint, so the pipe exits, turns upwards for a little, then turns horizontal again.

I would be grateful for opinions about what the cause of this excessive water and steam build-up is, and how it can be fixed safely.

kind regards
Mark

 

[ShaunCorbs]

Time for a gas safe engy to have a look

 

[Darren Jackson]

There should be a minimum 2 degree fall back to the boiler. On a 8m run that's about a minimum 256mm of fall required. there should also be inspection hatches installed so the entire flue length can be visually inspected. As ShaunCorbs suggests, Time for a gas safe engineer to have a look. Or better still request an inspection free of charge from a gas safe inspector who will then inform the installer if they find anything wrong with the "nearly new" installation and ask them to rectify any problems.

 

[Mark Gordon-James]

Thank you Darren and Shaun. I do indeed intend to have a safety check. Thank you also for the information about the fall required for such a long flue run, which I suspect could indeed be below requirement.

Would you therefore conjecture that it is the lack of gradient or fall back to the boiler that is the issue causing the hot water to spurt out of the flue exit intermittently? I would be interested if there are any other causes you know of?

 

[ShaunCorbs]

Could be or the at the boiler there’s a problem

 

[Darren Jackson]

With a flue installed without the minimum required fall back to the boiler, the condensate could pool in the flue and every so often when it has built up enough it could spasmodically cough and eject out of the flue terminal. Also standing condensate could cause future problems with corrosion and make the installation At Risk or even Immediately Dangerous and be condemned.

 

[Mark Gordon-James]

I see, sounds like that is the issue - much appreciated