Running waste pipe in joist spaces.

[chivers67]

Hi,

I've had my extension being built for a while now and rather than run a waste pipe down the side of my house, and dig up the path of solid concrete is it permissable to run a waste pipe in the floor over a four meter(ish) span?

The joists in my house luckily run in the direction the waste pipe will need to go so I was thinking of doing this internally. It will be a little fiddly but seems the best option to me, there's a cupboard upstairs that the soil stack can run up through so makes more sense as it will be hidden too

(sorry if this should be under plumbing but it's kind of building/plumbing combined)

 

[Richard C]

What's the waste run for, sink, bath, shower w/c; all 4? Building Regs allow a max 4m for an unvented sink/bath/shower branch in 50mm, 3m for 40mm; 6m for a 110mm soil run. Longer lengths are permitted if you vent the branch but any change in direction must be accessible from one end or the other for clearing blockages.

I assume your extension is being built under Building Regs. submission? If so it’s highly likely that your LABC will want to inspect both the pipe run & stack connection!

 

[chivers67]

The run is for a sink, toilet and shower for an unsuite. It will be in the 110mm waste pipe with a vent next door in a cupboard going up and out through the roof. This could be done down the side of our house but i didn't really want to do this and we live on a hill and our waste shares with next doors then out to the road they live up hill as well so there's not much in terms of play running it that way we'd probably have to raise the ground so it didn't show as it is our damp poroof on that corner is well over a foot higher than the drive/garden.

It's hard to exlpain. I'll have to take some pictures.

All with building regs all done properly but just need to crack on with the waste to finally finish and pass off. We've had three diferent neighbours since the start as one moved to a larger house, one had family issues and moved back to Oz and finally we seem to have neighbours who'll stay put so didn't wan't to approach them immediately as they moved in as we'll have to dig part of their drive up.

 

[Richard C]

Sounds OK subject to providing the required access points & falls. The soil run, waste connections, soil stack & new foul drain must comply with Part H of the BR’s & I would suggest you download a copy & spend some time understanding what’s required before proceeding. Assuming it’s a new stack & foul drain connection, you will need to provide a new (or connect into an existing) inspection chamber & LABC will want to inspect the new run & connections before you backfill; they may also want to witness a pressure test but don’t always bother.

 

[wsdconst]

saniflows are fantastic for this kind of problem if its not possible to run svp, the only downside is the cost of the unit,the fact it looks quite ugly behind the toilet,the whirring noise it makes when running,plus extra cost of fitting plus electrics.but on the upside you can put them virtually anywhere

 

[bathstyle]

As mentioned, read Part H fully, it'll probably take a full day of reading and measuring up to know whether or not officially this can be done.

Once you have it clear in your head, give BC a call and explain your plans, you may well know more about it than the inspector which is good, have the document to hand.

Get them to come out to inspect the work, if they do get you to do an air test then prepare well, it can be extremely difficult to get accurate readings from these tests so do what i used to do and install a plug hidden somewhere so you're only testing a small amount of pipe work

 

[Richard C]

saniflows are fantastic for this kind of problem if its not possible to run svp, the only downside is the cost of the unit,the fact it looks quite ugly behind the toilet,the whirring noise it makes when running,plus extra cost of fitting plus electrics.but on the upside you can put them virtually anywhere

Steer totally clear of macerators unless you have absolutely no other option; they are the invention of the devil . You will understand why the first time you have to stick your hands inside one to clear the inevitably jam; I'll leave the rest to your imagination

 

[Richard C]

if they do get you to do an air test then prepare well, it can be extremely difficult to get accurate readings from these tests

I’ve found mostly they won’t bother with air tests, they will only require you to bung the inspection chamber entry & fill the stack to the highest waste inlet & stand there with a watch; depending on the height of the stack, it may even be a tougher test!

 

[bathstyle]

I have only done a few in recent times, the biggest problem is the bungs, you go for a cheap set and the air will seep out of the little screw on cap.

Agree though, more often than not the inspector will stick his head round the corner, say 'that's fine' then 6ugger off