Bend in the boiler pipe without a handshake of carbon monoxide?

Soldato
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20,683
Just extend the flue further up straight.

The small pipe at ground level is probably the boiler drain or a safety blow off pipe from a hot water system. In either case I would not anticipate any real water flow from it.
 
Soldato
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Who installed that flue? Is it an existing install that's been modified?

The gray section is for a roof mounted flue not an exterior elevated flue.

There are very strict guidelines around flues and flue elevations.

I've not listened to your video but I will do shortly just putting the kids to bed.

Ok so listened now...

The plumber is correct you cannot have a bend in the pipe as the exit flue and intake pipe (flue is actually a intake and output pipe) have to be pointing the same direction. It's less to do with carbon monoxide and more to do with the vapour dispersing in a way that is correct, (to do with wind on the flue). The bend pipe you are talking about is called a plume kit and is only designed to be used on a wall exit not a chimney exit as you have (although th chimney exit you have is questionable). The right angle in th flue as it comes out the wall is called a diversion joint and you are limited to the number of them you can have in a flue.

The lower pipe that MUST be accessable is called a blowoff valve, it's the pressure release point if the boiler were to fail, the blowoff would drain the boiler of its contents, and have the potential to be at boiling temperatures, all new blowoffs have to be crimped to form a fan dispersal paturn so the water cools quickly.

As for the Engineer comment, your plumber is probably not gas certified, therefore is not a gas service engineer. Gas service engineers have to spend an absolute fortune getting qualifications and years of experience before being able to work solo! They then have to repeat the qualifications ever couple of years at great expense. Just for reference, I have a few different gas qualifications and I spend the best part of £6k every couple.of years to remain qualified.
 
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Associate
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Lower thicker plastic pipe looks like a condensate drain. Aa condenser boiler flue gases are of a lower temperature, because of that water condenses in the flue, runs back down into boiler and eventually out through the condensate drain. You could probably google for your Vaillant boiler manual and that will provide guidance regarding the condensate drain.

Flues are very strictly prescribed, it's one of the most regulated areas and for a very good reason as such a low level in the atmosphere can cause death. This is where you need a gas engineer.
 
Associate
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Earth
You'll get varying answer on this, I've not got boliers on my ticket as I don't need it but we all have to do ccn1.
What I will say though is manufactures instruction override everything so your gas safe engineer should of consulted that.
 
Associate
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move your hood over 3 inch all's good .. but the chimney needs space .. the bottom pipe is a blow valve .. just leave it .. it's only a sun screen just move it over .. if it's raining your not going to be there ..
 
Associate
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Just get a registered gas person to extend the flue upwards. No need for 90's or 45's.
They will check the boiler and work out the max equivalent flue length permissable for that model of Vaillant, and also advise you on the outlet pipe at floor level.
If it's a prv discharge, then it stays open and visible.
If it's from the condensate system, then it needs correctly discharging to a drain.
 
Associate
Joined
19 Aug 2019
Posts
241
Who installed that flue? Is it an existing install that's been modified?

The gray section is for a roof mounted flue not an exterior elevated flue.

There are very strict guidelines around flues and flue elevations.

I've not listened to your video but I will do shortly just putting the kids to bed.

Ok so listened now...

The plumber is correct you cannot have a bend in the pipe as the exit flue and intake pipe (flue is actually a intake and output pipe) have to be pointing the same direction. It's less to do with carbon monoxide and more to do with the vapour dispersing in a way that is correct, (to do with wind on the flue). The bend pipe you are talking about is called a plume kit and is only designed to be used on a wall exit not a chimney exit as you have (although th chimney exit you have is questionable). The right angle in th flue as it comes out the wall is called a diversion joint and you are limited to the number of them you can have in a flue.

The lower pipe that MUST be accessable is called a blowoff valve, it's the pressure release point if the boiler were to fail, the blowoff would drain the boiler of its contents, and have the potential to be at boiling temperatures, all new blowoffs have to be crimped to form a fan dispersal paturn so the water cools quickly.

As for the Engineer comment, your plumber is probably not gas certified, therefore is not a gas service engineer. Gas service engineers have to spend an absolute fortune getting qualifications and years of experience before being able to work solo! They then have to repeat the qualifications ever couple of years at great expense. Just for reference, I have a few different gas qualifications and I spend the best part of £6k every couple.of years to remain qualified.

Brilliant info. Thanks so much. I wonder whether I could get a crimp to disperse the water. Any idea why it collects algae? Because it's warm?
 
Soldato
Joined
27 Dec 2003
Posts
13,621
That flue install is shocking and the advice on here is bad advise

Firstly the pipe near the floor which people are calling a blow off valve is no such thing that's the condense discharge pipe and it should terminate to waste either into a foul water drain or into your sink/bath waste pipe etc it shouldn't be open onto the decking

The flue is a joke the white sections of flue with the screwed collars should not be outside at all its only designed to be used internally the flue should of been extended outside using a plume management kit

THe flue is also way too close to the guttering and the wood.

That's a proper cowboy job get a gas engineer in to sort it out
 
Associate
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Derbyshire
Before you go getting the wrong idea. Do some research, by contacting the manufacturer of the boiler.
Although quite a few manufacturers (Baxi, Ideal for example) will not allow white flue pipe externally. There are also manufacturers that do allow the white flue pipe to run externally. For example Worcester Bosch and more importantly Vaillant (your boiler). Vaillant even recommend extending the white flue externally to maintain any required clearances. They do recommend sealing the external flue clamps with weather proof silicone.
The Vertical flue terminal can also be used like it is in your installation, (even without a lead roof slate) as long as the terminal has the correct clearances around it. Which yours does not!

I've been gas registered for nearly 30 years, and spoke to a friend of mine who is a Vaillant engineer. The advise above, is what their technical department have said regarding your type of flue installation.

What I said in an earlier post still stands. Get a registered engineer out to get it sorted, although you are now armed with a bit more info. :)

Edit, it would appear that now (from 1st Sept) Baxi allow the white flue to run externally, but only using set dimensions from them, also external joints sealed with silicone.
 
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