Kitchen waste pipe

[MetManMark]

All
The house that we are renovating (it is old & we are converting it back to residential after years as a commercial use) has a kitchen waste pipe that runs under the floor and out of the house underneath the kitchen door. This is about 10 feet or so. One of the plumbers that came round suggested that this was a 1 1'4 inch pipe and that modern building regulations stipulate a 1 1/2 inch pipe. We need the building to be signed off by Building control (they are due to come round shortly to advise us on all the work that we intend to undertake). What should my approach be? Apparently he is a reasonable chap. Essentially we intend to have a sink and a dishwasher attached to this pipe. Surely it has been used for decades without a problem. If needed we will have to dig it out and replace it 🙁
Thoughts?
Mark

 

[Kev the gas]

Current min standard is 1 1/2 waste. Existing pipe is prob full of crap ect.

If the floor is to be tiled over ect I would suggest running in 2 inch pipe, bit of an overkill but the extra small cost is prob worth it.

 

[PlumbBobBob]

i agree existing pipe is probably full of crud. rerun in minimum of 1 1/2 which is 40mm even better to run in 2" which is 50mm.

 

[stevetheplumber]

surely underfloor should be 4inch drain

 

[MetManMark]

Thanks for the advice. So if I were to replace with a chunkier pipe what material should this be made of? Should it be sleeved to protect it?
Cheers
Mark

 

[Guest123]

surely underfloor should be 4inch drain

I agree, and the guy said it was 10 feet as well. Drain should be 110mm with a proper connection to outside main drain. Connections to it at sink should be as normal.

 

[MetManMark]

Thanks for the advice. The Building control chap came round and I drew it to his attention and asked what the deal was. He suggested that we check that there is no leak and then use it if it ok. He suggested blocking the outflow of the pipe, pouring a known amount of water down it and measuring it a couple of days later.
Cheers
Mark

 

[AWheating]

i guess you have a choice, if you believe the pipe is sound and not blocked up you may get away with leaving it alone tho it wont be to regs. If you are concerned that any future replacement after work is finished will be more costly and problematic it may be worth doing the work now.