convert external soil vent to AAV vs move it

[sandyman44]

hi,
I have a plastic soil pipe internal to the house exiting through the roof through flashing into an external soil vent projecting around a metre above the roof. The pipe is reachable in the loft, albeit a bit of a headroom squeeze as its near to the external wall. The external vent is right slap bang in the middle of the optimal place for solar panels on the south roof of the house, so it needs to go..

I figure I have two options, both involve sawing off the pipe level with the loft floor and then:

1. fit an push-fit internal AAV to it level with the room ceiling / loft floor. will be reachable from inside loft for service. loft is never going to get converted (not a usable space).
2. use flexi's, elbows and extension pipe work to redirect the vent to the north roof and refit there, exiting through the north roof as a similar type vent to now , or a vented tile.

option 1 is pretty easy and diy-able. solar installers will just remove the vent , make good the roof and re-tile leaving a unbroken roof prior to their install.
the AAV would be around 2.1 meters above the nearest input to the soil pipe (a bathroom with toilet, shower and bath).

option 2 more fiddly/messy (air pipe run across the loft) and requires a new roof opening to be made. solar installers could probably do it but more cost. is there a reduced diameter pipe I could sensibly (by which I mean, size reducers exist) use if doing this as its simply dry air?

any reasons not to do 1?


thanks

 

[Ian H]

I’d do option 1.

 

[Madrab]

yup ... option 1 normally .... but are there any other vented stacks anywhere else on the property?

 

[OvertonPlumber]

Fine till the dirgo freezes or sticks or creates suction. Just use one of these
https://www.google.co.uk/search?q=r...md=simvn&biw=360&bih=518#imgrc=NHpuAXruagpLnM

 

[sandyman44]

There's no other vented stacks on the house. All neighbours have vents. That's why I was pondering option 2. I presume running the air duct through loft if doing option 2 in 40mm waste pipe would be fine .

Thought about vented tile but same issue you can't cover it with a panel even though it's lower. I'd use that if doing option 2.

If the Dirgo has a fault I will be able to get to it easily
Unlikely to freeze it'd be at floor level in a well insulated loft. Surrounded by but obviously not covered by insulation.

 

[bernardgreen]

There's no other vented stacks on the house. All neighbours have vents.

Vents prevent positive pressure developing in the sewer pipes, hence sewer gases do not bubble up through the U bends in toilets, baths, sinks and similar.

An AAV prevent negative pressure developing in the sewer pipes hence the water in U bends in toilets, baths, sinks and similar is not sucked out of the U bends.

You need a vent pipe.......

 

[Ian H]

The sewer will have ventilation through neighbors stacks and gaps in manholes.

If option 1 didn’t work for whatever reason you could swap to option 2.

 

[sandyman44]

You need a vent pipe.......

which is what I was thinking.

what are the feasible options for an air duct across the loft out of the top of the stack? the only method I don't want to use is 110mm soil pipe ....

could one of these https://www.screwfix.com/p/mcalpine-drain-connector-110mm/3502v in the top of the soil pipe that I will saw off.
Insert short piece 40mm pipe immediately, variable angle bend (needs to match the roof pitch), long 40mm pipe up the roof, but then I don't know what size the input is on a vented tile, struggling to find specs for that, I'd assume it must be 110m so need to convert back. 40mm maybe a bit small for airflow?

another option would be to use 100 or 125mm ventilation ducting in round or rectangular or flexi, I could then come along the eaves and drop out the soffit with a fan vent grille even rather than going up to exit through the roof? that is pretty much 100% diy'able. I can't drop out the soffit near to the soil pipe as there is a window, but don't have to go far to get to a wall with no windows.
but I don't know how I'd join that type of ducting to the top of the soil stack. other than gaffer tape ?

I'd rather get this done at the same time as the panels as will have scaffolding up, roofers on site etc. option 1 first and then option 2 as a backup is fine in theory but needs roofers to come back later (much more cost) whereas if do it at same time as panels, much less hassle as roofers already there.