Plumbing question

Air to water virgin

Hi all

we are at first fix plumbing stage of our self build, we have a main bathroom upstairs about 15 feet away from our ensuite, our plumber wants to core two holes in the back wall of our house to bring out the waste pipes with two 4 inch pipes running down the wall,
my question is could we not join the wastes behind the neewalls and just have one 4inch pipe coming out the back wall ?
any help or feedback appreciated.

brianwalshcork

I’m not a plumber or a builder, but your proposing bends and joints internally... it might be fine, until it isn’t.

It won’t be spring water that’s leaking out of those pipes!

Dtp1979

Air to water virgin wrote: »

Hi all

we are at first fix plumbing stage of our self build, we have a main bathroom upstairs about 15 feet away from our ensuite, our plumber wants to core two holes in the back wall of our house to bring out the waste pipes with two 4 inch pipes running down the wall,
my question is could we not join the wastes behind the neewalls and just have one 4inch pipe coming out the back wall ?
any help or feedback appreciated.

You could, if it’s done correctly

BarryD2

An issue maybe that each trap (bath, shower, sink etc) should have it's own discharge pipe up to a point, where they join and then discharge into the waste system. If you join them in series, then water discharging down one pipe can suck the water out of the trap of another. Typically when you pull the plug in say the sink and your hear gurgling in say the shower, this is the case and to be avoided.

Dtp1979

A few air inlet valves would solve this

BarryD2

Dtp1979 wrote: »

A few air inlet valves would solve this

Doubtless but if you can avoid with conventional good practice, is that not better?

Dtp1979

BarryD2 wrote: »

Doubtless but if you can avoid with conventional good practice, is that not better?

I wouldn’t tee small waste together. I’d only join them into 4” along a route. But yes, if it can be done properly, then do

Big Eejit

Dtp1979 wrote: »

I wouldn’t tee small waste together. I’d only join them into 4” along a route. But yes, if it can be done properly, then do

I had two toilets teed to one soil pipe in a previous property. Flushing one toilet would flush waste partially into the other.

I’m not a plumber, but I understand (from speaking to a reputable plumber) that the job wasn’t done well and while not the best way to do it, it can work, but only if the pipework is angled correctly.

Tullogher

Big Eejit wrote: »

I had two toilets teed to one soil pipe in a previous property. Flushing one toilet would flush waste partially into the other.

I’m not a plumber, but I understand (from speaking to a reputable plumber) that the job wasn’t done well and while not the best way to do it, it can work, but only if the pipework is angled correctly.

Look up the building regs on drainage. Good pictures in there with max lenght to stop breaking traps and letting smells out.