Boiler flue stains

[Dick'll Do It]

Hi Guys
Can you help me or at least point me in the right direction.
I have a problem at my own house where the flue from my oil boiler comes out the side of my built in garage.
I had 3 x 2 flags down on the outside and thought that the rust stains on the ground were coming from a metal heat guard. Due to the height of it i decided to remove it and do without.
I have repaved the area but within 3 months its back with avengeance.
I asked a local plumber if the boiler was leaking but he said the garage floor would be wet not the outside.

Does anyone know what is causing this?
Thanks for your help in this
Richard

 

[Rickster123]

When was the boiler last serviced?

 

[Dick'll Do It]

Last service was 10 months ago. problem has been going on for years.

 

[Geyser]

Didn't hit the oil pipe when repaving did you? Can you smell oil?

 

[Dick'll Do It]

Hi Geyser.... new oil line fitted when paving was lifted and no smell of oil anywhere

 

[SimonG]

Water and metal will give you rust. Add in the heat and even stainless will go. Wall looks really wet around flue and it hasnt been the driest of autumns/winters.

Is there any steam come out when it first fires? Could be pin holed inside combustion chamber.

 

[Rickster123]

Not a dripping guttering joint above the flue?..

 

[Dick'll Do It]

Hi This is what the boiler looks like when running. This video shows it after being on for a couple of hours


[video=youtube;vxEka6CxGJE]https://www.youtube.com/watch?v=vxEka6CxGJE[/video]

 

[Dick'll Do It]

Not a dripping guttering joint above the flue?..

No guttering above it

 

[Best]

If it is not rust coming from the stainless steel flue, then it must be sulphur from the gases which looks identical to that rusty colour. I see this on roofs - on the tiles/slates and on the lead slate on jobs where the flue is conventional vertical with rain cap. The water and sulphur from the combustion mix and drip onto roof.

 

[Best]

Those type of flues are poor IMO because they throw the gases and plume against the wall.
A balanced flue that puts the fumes straight out is much better.
What sort of boiler is it? It can't be condensing with that flue. Maybe get your service engineer to check combustion isn't too fine set. Also consider new boiler and flue. Grant Vortex with Grant flue kit I prefer

 

[Dick'll Do It]

Those type of flues are poor IMO because they throw the gases and plume against the wall.
A balanced flue that puts the fumes straight out is much better.
What sort of boiler is it? It can't be condensing with that flue. Maybe get your service engineer to check combustion isn't too fine set. Also consider new boiler and flue. Grant Vortex with Grant flue kit I prefer

Not a condensing boiler. Warmflow boiler approximately 18 years old & never had a problem. I don't think it's rust as this stuff is eating a hole in the new paving after only 3 months

 

[Rickster123]

Not a condensing boiler. Warmflow boiler approximately 18 years old & never had a problem. I don't think it's rust as this stuff is eating a hole in the new paving after only 3 months

What readings did your service guy get on the last service?

 

[Dick'll Do It]

What readings did your service guy get on the last service?

Sorry APPlumbing I've no idea

 

[lame plumber]

stick a plant pot under the flue outlet.

 

[Sparkgap]

Not a condensing boiler. Warmflow boiler approximately 18 years old & never had a problem. I don't think it's rust as this stuff is eating a hole in the new paving after only 3 months

Sounds like acidic condensate. What fuel are you using?
Sudden thought, does the boiler have a condensate trap and outlet and if so should/does the flue slope back so any condense runs back into the boiler and out the trap instead of dripping outside?

 

[SimonG]

OP said earlier that its not a steamer. Think it needs looking at inside the combustion chamber. Couldnt tell on the video wether the steam was coming off the wet flue or from the flue itself.