Soil stack distance from boiler flue pipe distance

What is the minimum distance that a horizontal boiler flue pipe has to be away from a vertical soil stack outside where the flue pipe exits the wall?

 

Whatever it says in the boiler's installation instructions

 

So each boiler has a different spacing even with the same 100/110mm diameter flue exit? I thought it would be down to gas regs.

 

Sometimes, as above go by the MI's.

 

So would 250mm between the outer edge (350c/c) of each pipe be too close, taking an average of most boiler instructions?

 

Not possible unfortunately, MI's are boiler specific. An average could be wrong.

 

Manufacturers instructions override gas regs, and must be adhered to. You can't apply some arbitrary average of your own, you must follow what it says in the book.

 

Is the soil stack plastic?

 

yes it will be plastic. Never realised the manufacturers instructions varied so much so may have to look at switching the upstairs bathroom toilet position so the soil pipe exit is in a different position and the soil stack can be moved further away from the boiler wall flue. It's too close now and the last thing i want is long runs of ugly soil pipe running horizontal to meet the stack.

 

It's not my area but my boiler vent has a bit of bent aluminium above it, as the upvc soffit is close.
Could /would a shield of aluminium be of use?

 

What boiler do you have?

 

No. The aluminium on your soffit is to prevent the damp exhaust rotting your soffit. It doesn't allow the clearance distances to be changed

 

No boiler specified yet as SAP need to be involved. Just in the design process for a build. Neither pipe will be near a soffit as they are on a large gable end. The best way to describe it without showing the plan is... The boiler is on the ground floor and theres an ensuite above it on the 1st floor with no window. Where the 1st floor toilet would exit the wall and turn to join the soil stack, the stack would be quite close to the boiler flue outlet. Probably 250-300mm between both outer edges of the flue and stack.

So going by the comments above, it's a bit tight with the minimum dimension unknown at this stage, so to play it safe I'll have to look at repositioning the soil pipe and or toilet to allow a greater distance between flue and stack but also avoid long runs of horizontal soil pipe. Hope this makes sense.

 

The soffit is UPVC,