3.5 inch waste?

[cb9002]

My house has a CI 4.5" internal soil stack. In the upstairs bathroom, above the first branch pipe, it is reduced to a 3.5" CI pipe.

I'd like to cut the soil stack level with the sink overflow and use a dirgo. However, I've only seen them in 4.5". Can anyone source a 3.5" dirgo or an adaptor? Replacing the soil stack isn't an option.

Otherwise, instead of using a dirgo, could I seal the top of the pipe and take off a branch somewhere lower in, say, 40mm and run that as an external vent pipe? I could use a HepVO valve on the sink for air admittance.

Thanks

 

[grrinc]

I think Durgo do an 82mm one, but I am not sure. If not, use a 3 1/2" pan connector from Multikwik to adapt.

http://www.multikwik.com/product_detail.php?recordID=MKS3

 

[Softus]

Why do you think you need an AAV anywhere?

BTW, you can't assume that it's a valid thing to do to replace a roof-level vent with an AAV inside the house. This is a material change to the drainage system that you're required to consult your BCO about.

 

[cb9002]

Why do you think you need an AAV anywhere?

Don't need, want!

I currently have the soil pipe coming straight up through the middle of the bathroom, not the most asthetically pleasing situation! I guess the builder/architect couldn't be bothered with an extra few quid to run it in the cavity or outside.

My plan was to cut off the vent pipe at highest overflow level (top of the basin) and replace with a durgo, allowing me to put in a worktop, cabinets and concealed-cistern WC, hiding the soil pipe.

I'm aware that the sewage system needs to vent somewhere, this is why I'm wondering if it would help to take a vent pipe somewhere (floor level under the cabinets?) and run it externally. On the other hand, I'm in a mid-terrace and was under the impression that only houses at the end of runs needed an open vent.

Further advice welcomed, thanks!

 

[Softus]

Why do you think you need an AAV anywhere?

Don't need, want!

I beg to differ, viz:

I could use a HepVO valve on the sink for air admittance.

So, once again, why do you think, if you do what you're proposing with the stack, that you need an AAV for the basin?

I currently have the soil pipe coming straight up through the middle of the bathroom, not the most asthetically pleasing situation!

So just box it in then.

I guess the builder/architect couldn't be bothered with an extra few quid to run it in the cavity or outside.

You can't run a 4" soil pipe in a cavity. And inside in in vogue, not laziness.

My plan was to cut off the vent pipe at highest overflow level (top of the basin) and replace with a durgo, allowing me to put in a worktop, cabinets and concealed-cistern WC, hiding the soil pipe.

Modification of the stack in that manner is notifiable work, which is why I suggested that you ask your BCO whether it's acceptable to do it.

 

[cb9002]

Softus, I understand its notifiable, but am still checking here before I but in a buildings' notice.

Why do I think I need an AAV at the head of the soil stack if I remove the vent pipe? To prevent siphonage.

As to the HepVo trap, it was merely a thought. It had been suggested that a single durgo may not provide a quick enough air inrush to prevent siphonage when the toilet was flushed, therefore a HepVo trap would provide additional protection.

Boxing won't work in this case, otherwise I would have done it.

 

[Softus]

Fair play cb9002, you seem to be on top of what you're doing. It's clearly a dilemma, so hopefully the BCO will decide that there's enough venting in the neighbourhood so that you can achieve what you want to.

 

[cb9002]

OK, thanks for the help!