Connecting new WC/shower into 3" stack

[duotwr]

Hi,

looking for some thoughts on this - am trying to work out how to get drainage sorted for a new downstairs shower room and WC.

I'm on a combined rain/foul sewer system - and currently upstairs basin/bath plus downstairs washing machine/dishwasher/sink all connect into existing 3" rainwater downpipe.

This downpipe is about 1.5m from where a WC might come through the wall. Can I connect new WC/shower room into the existing 3" pipe. Sounds an awful lot of connections going into one undersized downpipe.

Invert level for this downpipe is about 1.5m below the outside surface - so getting down to that level for a whole new waste pipe sounds like a big task.

Any thoughts on what might be easiest?

thanks in advance
K

 

[denso13]

Can I connect new WC/shower room into the existing 3" pipe.

No, that's too small for a WC.

What does the downpipe go in to at ground level? The main drainage would normally be just below the surface.

 

[duotwr]

Thanks for reply - risk I'm using terminology wrong!

The 'downpipe' is cast iron (house dates from 1970s) and disappears straight down underground. Alongside this is a surface drain that appears to drop down to the same level - which is where I'm getting my c. 1.5m depth estimate from. Upstream (unfortunately in the wrong direction from new WC location) is a deep manhole into which the main soil pipe from upstairs toilet connects into.

Our house sits above the road level by a couple of meters (sloped front garden) which is why I'm assuming the depth of the main drain down the side of the house is so low.

K

 

[denso13]

The 'downpipe' is cast iron (house dates from 1970s) and disappears straight down underground

It would normally enter 4" drainage just below the surface, they wouldn't take cast iron to any depth. Have a dig around the bottom of it, you may be able to connect the WC there.

The cast would also need to have sealed joints and terminate above roof level to act as a proper open vent.

 

[duotwr]

Ok - useful to know about change in depth below surface. I'll have an investigate. We've been in the house about 4 years - unfortunately none of the neighbours know more than I do!

The cast iron pipe terminates up above roof level.

I want to try and have a chat w Building Standards people (I'm in Scotland) - they may have some ideas - we live in an area that was built out at scale in the 1970s by Wimpey - so am sure lots of similar questions come into them.

K

 

[denso13]

want to try and have a chat w Building Standards people (I'm in Scotland) - they may have some ideas

Not really what they do, on the other hand if you make them aware they might just ask for a Building Warrant application, with associated plans, as what you intend doing should strictly have one.

Whereabouts are you, roughly.

 

[duotwr]

Bishopbriggs north of Glasgow