drainage query

[basandjane]

Hi all not sure if this is in the right section, But i have a query to do with drainage .

I want to split an upstairs bedroom into an on suit, the problem i have is the drainage for toilet ect,
Now the main drainage stack is on the other side of the house, though there is a wc, cloakroom below the location for the on suit, does any one know can i extend the current drainage pipe up to the on suit? this drainage pipe is pvc and just supplies drainage for the toilet and cloakroom sink, strait outside to the main sewer and does not seem to be vented?

will i need to run a complete soil ,vent stack up to the roof?
Or can i run it just up to the on suit ?
Am not sure on the venting issues and regulations would be very grateful for any info and ideas.

many thanks and excellent forum.

 

[noseall]

if you intend building a vertical stack to collect an upstairs toilet then it would be wise and not much extra effort to extend the stack so that it could vent.

so long as there is external ground floor drainage local to the proposed 1st floor toilet then i can see no problem. the falls are dealt with vertically.

 

[Richard C]

Can’t believe how many of these are cropping up lately! As nose says, yes it's perfectly feasible to extend your existing foul drain. You don’t need to vent a w/c at ground floor as long as it’s within 1.3m of the drain invert – that’s the horizontal bit in the ground. Once you go over that, the stack has to be vented & this can be done using an AAV (Durgo) on the top of the stack either inside the new room or in the loft but it must be higher than all the overflows; but you can only use an AAV if there is an open vent on another part of the drainage system to take care of venting positive pressure. Otherwise extend through the roof & open vent to air. Make SEPARATE connections to the stack for your w/c, shower/bath & sink unit if you can or you will create other venting problems & draw the traps.

If your forming an en-suite & using a stud partition, be aware that any stud wall (even existing ones) between a room containing a w/c & another habitable room (bedroom) must be formed using sound block plasterboard with a min. 25mm mineral wool internal insulation. If you’re just forming the en-suite in an existing bedroom that has solid block walls it’s OK, you don’t have to sound insulate the room the en-suite serves.

Other regulations to be aware of are the room must have means of ventilation; you don’t have to have a window, an extractor fan will do but if you have a shower or bath in there, you must still have a fan even if there is a window. ANY electrical work in a room with a shower or bath must be done by a part P spark & certified to BS 7671 - you can DIY but it gets involved! The work your doing is also notifyable so you are supposed to tell your LABC & pay a fee for them to inspect & certify it complies with current Building Regulations, if you can’t produce a completion certificatewhen you come to sell up you could have problems.

 

[basandjane]

Thanks for your reply.s has been most helpful, will run the stack to the roof and vent, was just a little unsure how awkward it is to run the vent through a sloping tiled roof.
Also need to run the stack vertically through the wall its running up to run the other side of that wall, any helpful comments on this would be great like does the stack have to stay the same diameter through out? and holes to be drilled through cavity brick and stone?

thanks again for you help.

 

[Richard C]

will run the stack to the roof and vent, was just a little unsure how awkward it is to run the vent through a sloping tiled roof.

Not very, it’s standard practice.

Also need to run the stack vertically through the wall its running up to run the other side of that wall,

What you mean run vertically through the wall; As walls are usually virtical, it’s usual to run horizontal through them; are you talking of a dog leg? If so there are other possible problems associated with doing that! Always keep the stack vertical if you can & run all the services into that. Why cant you keep the stack the other side of the wall? It doesn't have to be in the same room as the facilities!

does the stack have to stay the same diameter through out?

It can get complicated & not worth the hassle so it’s easier to say yes.

and holes to be drilled through cavity brick and stone?

You can use a core drill (but 110mm is rather large) or it can be done using just a long masonry drill & a breaker. It can be hard work but nothing out of the ordinary.

 

[basandjane]

Thanks again richard.

There was two reasons i was gonna run it the other side of the wall ,one because its into the garage saving the need for boxing in. and the other is that the location it would run at present would bring the stack out into the ajoining bedroom and not the onsuit bearing in mind have yet to put the stud wall in yet. i suppose i could re angle it under the floor boards once i reach that far and up through the on suit into the loft? or even better through the stud wall its self mm?
And yes i did mean horizontal through the wall, the other problem maybe the wall it follows up has been knocked down on the first floor,( shame would have saved me putting in a stud one) but that might hinder me from running the stack horizontally once up to floorboard level?

now im just confusing my self, need to rip those floor boards up and have a look.

 

[Richard C]

Although Building Regs. don’t prohibit offsets in the wet portion of the stack they are not really a good idea. An offset can only be designed by using 2 x 45 degrees bends, if you run horizontally (say through the wall) & then vertically again my understanding of the regulations is that that you must provide access points in case of blockages; this & the amount of space 2 x 90 bends will physically take up will make getting it all under the floor boards impracticable & probably impossible. The regulations also prohibit any branch connection within 750mm of the offset which in most cases (including one I had) means that it doesn't really help as you will then need to mount the w/c half way up the wall let alone providing boss inlets for the sink & shower wastes! If you can offset much lower down (in the garage?) then that would be viable but I don’t know the location of your walls. If you keep the stack virtical & tight against the wall, boxing in doesn’t really notice that much once it’s all plastered up & decorated & it is standard procedure. The only other option is to extend/shorten the drain invert below the ground floor to move the whole stack over but I guess that would involve major disruption to the ground floor cloak room.

I’ve attached links (for the umpteenth time it seems!) to the Building Regulations Part H;

http://www.planningportal.gov.uk/england/professionals/en/4000000000382.html

& a very useful design guide which also covers BR requirements;

http://www.hunterplastics.co.uk/pdf/soilandwaste/swt_brochure.pdf

The regulations can be a pain &, at times, sticking pins in your eyes would seem like a welcome distraction but once you understand them they are not particularly difficult to comply with & it keeps it all legit. I would advise you download & study these documents before you go any further as they will give you a good idea of what you can & can’t do. If you notify the work (& you should!) the installation will be inspected so it must comply with the regs. or the Building Inspector will reject it. Don’t forget you need to sound insulate any stud wall between the w/c & another habitable room!

 

[basandjane]

Thanks alot richard you have been a big help, keep up the good work bud.


ben