Building extension over kitchen gully trap

[Shevek]

We're building a near-full-width rear extension to our mid-terrace house, which will extend over the existing kitchen gully trap position. We're leaving the kitchen sink where it is, so we'll still need the drainage, but it's a kitchen island so no route to the external wall. See attached image, which shows *existing* underground drain positions.

We're are putting in a new slab in the kitchen area but even if we took the kitchen waste through the slab to the outside wall it would be too low to then drop into a gully trap because floor and ground level are much that same at that point.

Any thoughts on how best to drain the kitchen waste water? Just drop it into a sealed pipe and run straight to manhole? Stub stack and AAC perhaps?

 

[stevetheplumber]

run a new drain to where the sink will be and drop straight in

 

[Howsie]

Welcome to the forum. It's your builders problem surly?

 

[Shevek]

run a new drain to where the sink will be and drop straight in

Cool, ta, and how do I stop odours/rodents?

 

[Shevek]

Welcome to the forum. It's your builders problem surly?

Thanks. It's self-build.

 

[PlumbBobBob]

it that case get building control to advise you

 

[Shevek]

it that case get building control to advise you

Well when I say we're doing it self-build, I'm an architectural technician and the builder will be my father who is a builder of over 40 years experience (in NZ).

I was just hoping to get some ideas before submitting a building control application.

 

[Howsie]

You need to know the rules and building control will advise you of this. It'll save you a lot of time and money in the future.

Not aimed at you, but the amount of self builds I've been to that are thrown up without knowledge of the building regs worries me.

 

[Shevek]

True, but it's also my job to know the regs. I'm going to discuss with building control officer but I was hoping to get some ideas before submitting a proposal. Guess I could speak to officer before submitting.

 

[jase158]

yes treat them as a friend, they will give you less hassle if you do, find out any rules that will effect the build, this is there job, they will tell you whats needed before you even think of it. then when they come to check they will see that you have done what they told you to do and leave you alone

 

[Howsie]

True, but it's also my job to know the regs. I'm going to discuss with building control officer but I was hoping to get some ideas before submitting a proposal. Guess I could speak to officer before submitting.

That's the best way. You have it from an authority then and not some dodgy plumbing forum 😉

 

[lame plumber]

Well when I say we're doing it self-build, I'm an architectural technician and the builder will be my father who is a builder of over 40 years experience (in NZ).

I was just hoping to get some ideas before submitting a building control application.

with your combined knowledge it shouldnt be an issue to know what to do, but talking to bc is my best advice, once they and planners approve your plans, they cant change their minds and that can be very useful when all the different bc officers keep turning up on site with their own opinions.

 

[Shevek]

Talked to my BC man and he said it's fine to just bring the 100 mm drain up to floor level then reduce to 40 mm and run to sink. As someone on another forum said, just make sure you use a nice deep trap and make sure manhole is vented by a stack pipe.