HELP - bath waste problem

[pt44]

Hi

I've just started work on a bathroom. I'm replacing the bath, basin and toilet. After taking up the first floor panel (nice chipboard - which is poorly laid and needs either re-screwing or replacing) I noticed that the bath waste (which is no doubt linked to the sink waste is at a very shallow angle.

I've removed a floor panel approx 1.8mt from where the bath sits. The waste pipe has been laid with its top edge flush with the top of the floor joist i.e. just under the floor panel. Madness surely? There cannot be any drop between where it enters the floor next to the bath and where it reaches this point! The pipe then has bends to drop it approx 2 inches and 90 degrees, so that it then joins into the toilet stack.

At the bath end, there is a valve fitted - which I presume is an anti-syphon valve? Seems to have an air inlet at the top of it, just under the cap.

Now I can understand why they have done all of this, so as not to cut too deep into the joists (which are approx 6 to 8inch deep) but it seems madness not to have any kind of drop on the waste pipe?

So - what to do? I know from experience that it is fine to make holes in the centre of a joist, to pass electric cables through etc. Does the same apply to plumbing? Can I make that large a hole - without harming the joists strength. Is there another solution or way around this. It must occur often, where the waste pipe has to cross joists.

I suppose if it is a problem, I could possibly re-route the waste through the outside wall and then into an outside drain - presuming one is available. Need to check.

Any help/guidance much appreciated

Paul

 

[sonray ltd]

taking it as a 8" joist.
the max notch out of the top must not exceed 25mm
the max hole through the centre must not exceed 50mm
and must be in certain distances depending on the lenght of span of the joist.
and no hole must be within 4" of a notch.

 

[pt44]

thanks sonray

I was just reading this post
http://www.ukplumbersforums.co.uk/sanitary-ware/178-waste-through-joists.html

which as you say seems to indicate that if necessary I can make a hole big enough to take the 40mm waste pipe through the centre of the joists. Thereby giving it some drop.

Any recommendations on how to drill these holes? I presume a hole drill on an angled drill? or is there a better way?

And presumably keep the holes as close to the centre of the joist as possible. So if I go for a drop of approx 25mm over a metre, if I start at approx 1 inch (25mm) above the centre line and finish approx 1 inch below, at a 2mt distance, then that would still mean that the pipe hole was which is 40mm in size, would end up 2 and a bit inches from the top of the joist at the start of the run and 2 and a bit from the bottom of the joist at the end of the run.

Which doesn't seem to be much. So perhaps I will use the strengthening method of 18mm ply screwed to the joists, when it reaches the each end.

Does that make sense?

Paul

Paul

 

[Mike Jackson]

You could fit a HepV0 valve with a right angle adaptor. This could raise the height of the waste pipe sufficiently.

Mike

 

[pt44]

You could fit a HepV0 valve with a right angle adaptor. This could raise the height of the waste pipe sufficiently.

Mike

How so? I know what a hepv0 valve is - but I don't see how it would help?

Paul

 

[Mike Jackson]

With the right angle adaptor it brings it up very close to the bottom of the bath. With the bath at standard panel height it could give you a couple of inches extra height over a standard p trap.

Mike

 

[pt44]

With the right angle adaptor it brings it up very close to the bottom of the bath. With the bath at standard panel height it could give you a couple of inches extra height over a standard p trap.

Mike

Thanks mike - trouble is, the bath height is not the problem. The waste leaves the bath at a good height and enters the floor. However, it then right angles and the previous plumber has notched out the joists, so that it sits just under the floor boards all the way along. i.e. zero drop. Its not until 2mts later that it exits and drop a couple of inches, then has a slope of another 1mt to enter the stack.

Its this 2mt section that is my problem.

Paul

 

[sonray ltd]

you'll probably find that it was originally above the floor level before dropping into stack

 

[justlead1]

Hi. Having single stack soil and waste systems drummed into us at tec. I fail to understand how 80% of new bath/shower rooms are in compliance with the codes of practice. The same reservation that i have will be shared by carpenters if you elect to accommodated waste pipe through joists. It a,int a perfect world. The fact that someone fitted a anti siphon device, suggests the water empties to quick, (Probably to combat the noise rather than potencial smell.)
Why not speak to the client, gain history of the waste performance. Offer them the oppertunity of conneting to same or running it around the wall of the bathroom, it's against the grain. But even Kings abdicate some times. Good Luck

 

[sonray ltd]

anti siphon device, suggests more of a blackflow problem than running away to quick.

 

[pt44]

I've convinced the client to let me run the bath waste around the wall, behind a boxed in skirting board. This will give me ample drop. I can then go down through the floor and connect to the existing pipe next to where it connects to the stack.

The current basin waste, I will improve and go over the existing notches. This won't give me much drop over the 1mt run, but should be at least 10mm, which is FAR, FAR better than it was.

After fully removing the floor today, I discovered the wonders of the previous "professional" plumbing job. The bath waste goes upwards to the other end of the room - only just up - but still up (not down!). Once it right angles and heads for the stack, they have connected to the old pipe with a compression fitting, which is where the whole pipe sags. This therefore sags and gives a nice uphill run (again) for the water to try and make its way to the stack (which incredibly they've actually managed to run downwards (must have been a different plumber).

All in all, the most hilarious installation I have come across. Oh, I forgot to mention that even the short run for the basin waste was angled downwards away from where it should have been flowing. God only knows how this installation managed to get rid of water. Sheer luck. The pipes were still full of residual water - as there was simply no way it could drain away.

Thanks for all the help chaps.

Paul

 

[justlead1]

Hi. You may well be right. How ever the design of singe stack soil and waste systems is based on waste pipes never running full, allowing air above the flowing water at all times. This design protects the trap on the sanitary fitting from siphoning and allowing foul air into the accommodation. Good luck

 

[Kings]

it's against the grain. But even Kings abdicate some times. Good Luck

Hope you're not talking about me!