new WC soil pipe route

[zig1]

Hi,

Thanks for reading - this is the first post I've made on the forum, and I've not got much plumbing experience so far!

I've been puzzling as to whether an under stairs toilet can be fitted in the house. I've read in the building regulations that any connection into the soil stack must be more than 450mm above the drain invert, and I suspect that a new soil pipe would meet the stack lower than this.

The soil stack invert seems to be buried in concrete, heading down under the concrete kitchen floor, so it looks very difficult to ascertain the level of the invert! I'm also wary of connecting into this, as it's quite an inaccessible area to get to and it's an internal stack.

It then occurred to me that maybe a new soil pipe could connect directly to the outside drain that serves the gutter and grey water, if I connected downstream of the gulley. The drainage all combines under a manhole in the backyard, so it definitely goes to the sewers, and I guess the connection would be within the 1.3m height drop regulations from the WC.

Here's a picture of what I'm thinking of doing-

Untitled

• zig1
• 19 Oct 2014
• 1

Anyone got any ideas if this is a viable plan?

Many thanks!

 

[Norcon]

The 450mm rule won't apply to your situation so just take the shortest and easiest route.

 

[Hugh Jaleak]

I'd steer clear of trying to connect to the stack, it's an unknown quantity and as you say, difficult to get at. Connecting to an external drain would be the easiest option, but the route you're assuming in green is a definite NO! Bends in horizontal drain runs are only allowed immediately outside of inspection chambers, otherwise drains must be laid to a straight line with a suitable fall. Building Control would need to be notified and it's highly unlikely your proposal would be allowed.

You need to be looking at a straight run from the proposed WC position, under the floor through the kitchen to couple onto the existing run. Where the drains are already needs establishing, I would think it very unlikely there are 2 parallel runs as shown in your sketch, I would expect the soil and gulley to join pretty close to that corner. You don't want to be trying to join onto an existing drain under the floor!

Once a suitable connection point is established, you'll need to allow for a chamber at that point to provide rodding access back towards the new WC. Depending on depth of drain at that point will deem if you can use a small shallow chamber, or if you need the bigger 450mm diameter chamber. If you're planning on digging yourself exercise caution with regard to buried services, gas, electric, water etc.

 

[zig1]

Hugh - interestingly the drainpipes join at a manhole, which is actually about 7 metres from the gulley. There is already a toilet at that end of the kitchen, which I'm trying to move under the stairs to expand the kitchen area. I've redrawn the picture to include the manhole and kitchen WC. There's also two other guttering drains running into the same manhole that I've not marked.

Untitled

• zig1
• 19 Oct 2014
• 1

I'm wary of running the soil pipe straight through the kitchen because it has a concrete floor, and it is 6 metres long. Also the main soil pipe from the stack must take a turn before it reaches the manhole, because it enters at 45 degrees to the wall of the house.

I think gas and electrics enter at the front of the house - I'll double check! Mains water does enter through the backyard though.

 

[Hugh Jaleak]

At the moment I think you're onto a bit of a non starter. I really cant see the BCO letting you run a drain along the green line, you've got a 90 bend buried under the floor, unless you fit a chamber there, but do you really want a chamber in the dining room? (It may not be permitted internally anyway.) I think before you go any further it's time to ask Building control what they would allow, and work your plans from there.

Alternatively, it's either leave WC where it is, or there (if you really are absolutely desperately determined to move the WC and cannot face life without a bigger kitchen) a Saniflo. Although I hate those things with a passion, they are not very sanitary and often don't flow either..... Lastly, if you've women in the house then forget you've ever read this paragraph.

 

[zig1]

Yes it's looking a bit difficult, and I'm not that keen on the saniflo idea as well. Maybe an outdoor toilet... I'll ask building control for some advice and also speak to a plumber about it as well. Thanks for all the advice.