soil vent pipe connection question - using rectangular ducting

latecomer

We've had the cowboys in and one of the things I need to fix is the soil vent pipe which goes up from ourside the new showerroom in the loft, up the combe ceiling and out to a vent. They used flexible PVC tubing and it got shredded as they forced it in (funny that given all the slate nails coming through on the underside of the sarking .... idiots :mad: ).

Anyway I'd rather use a solid pipe and my thought was to try and use some of the square section plastic extractor ducting to give me room to put up some wooden straps below it. I'll need to come round 45 degrees, then straight down the coombe and then back into standard grey pipe.

This is what I had in mind:

square duct

with these on the ends

Square to round connector

Problem is that the grey pipe coming in from the vent is 100mm internal and about 110mm external so I'm guessing these are not going to fit together. The gap between the sarking and the plasterboard will be approx 5" minus whatever the nails protrude. I dont want to use the flexible ducting if I can avoid it as it will almost certainly get punctured on the nails.

Anyone tried something like this or have any better ideas?

This is a (very ) rough picture of what I'm trying to achieve, red line/arrow shows where I had hoped to use the rectangular section ducting:




Thanks!

eco-friendly_2

I'm assuming you've got nothing exiting the roof at the moment...


You can't use rectangular ducting for a soil vent, and there's no way you would be able to make it watertight. You will need one of these a length of [URL="http://www.toolstation.com/shop/Structural/Grey+Soil+Vent/Pipe+110mm+x+6m+Pack+2+x+3m+Grey/d210/sd2804/p92968]this"][/url]this and [URL="http://www.toolstation.com/shop/Structural/Grey+Soil+Vent/Terminal+Vent+Grey/d210/sd2804/p66048]that"][/url]that .

You might be able to install an air admittance valve instead, a durgo.

latecomer

Thanks for the reply. The vent is already in place and where I drew the red line/arrow on the diagram was a length of flexibe ducting which was shredded by the nails when they rammed it in. I'l have a closer look at it tonight.

27col

If you have got the vent already in place why not just use 110mm soil & vent pipe to do the installation. By the way, has the vent through the roof got an apron fitted to it so as to ensure water tightness.

latecomer

The rafters are 5" deep = ~127mm. The soil and vent pipe is 110mm OD, which would leave 17mm for the 135degree bend and to stay clear of the slate nails - which is why I was looking at alternatives.

andrew-b

Could you not widen the gap behind the plasterboard and roofing felt by battening out a little - not necessarily the whole wall? Presumably some of the board has had to be pulled off already to gain access? Hope you don't find too many more cowboy spur marks!

phill99

A Durgo (Air eliminator valve) would be a better option then there is no need to put the soil stack through the roof.

latecomer

Can you use a durgo type valve when there is no other vent for the soil pipe?

The showerroom is in the loft conversion of a bungalow so there isn't much vertical height if the vent/valve needs to be a certain distance above the connections.