# Pipe under joists

According to my Onsite Guide (for Electricians) the maximum hole diameter should be 0.25 * joist depth. The maximum depth of a notch should be 0.125 * joist depth.
Holes should b on a centre line in a zone between 0.25 and 0.4 * span of joist. (This requirement is usually ignored) Notches on top in a zone between 0.1 and 0.25 * span of joist.(This requirement is usually ignored)
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35mm means a big hole or notch out of the joist. a lot depends on the position of this notch relatie to the size of the joist and its position away from the support which affects the forces acting upon the remaining wood.
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I'm still curious as to how Dave gets his 40mm waste through a 35mm hole.
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BillP wrote:

Christ! Are his turds THAT big?
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wrote:

If he's been drinking Guinness the night before.....
PoP
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I haven't read any of the replies as there are to date 38 of them but I am curiouus to know what the waste is running along and running to.
If you are upstairs and the pipe is run level with the floor or ceiling then drops away at the wall to the drains below, how much fluid do you suppose will remain in the level part of the pipe? And what danger or threat will it pose?
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On Sat, 11 Oct 2003 20:45:20 +0000 (UTC), "Michael Mcneil"

I fixed a problem in our loft two days ago which has been there since the house was built. The bathroom ceiling developed a damp patch.
Problem turned out to be that the joint in the plastic pipe immediately above the damp patch had never been sealed - the joint was just pushed together. The pipe ran horizontally across the rafters and carries no fluid directly - it is the breather pipe that vents to the roof from the toilet soil stack. The fluid was condensation from the stack.
I solvent welded the joint and the ceiling has dried up.
The moral of the story here is that for the pipe running horizontally to work then there would be a joint (probably right-angled) at either end. It may be that one of those joints might not be securely made, or perhaps fail some time in the future. If that did happen you might have fluid which seeps out and ruins the ceiling below (or perhaps causes rot in the joists). And as noted for my problem above, any moisture within the pipe might not be a direct corelation with what is being carried - it might just be condensation.
PoP
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PoP wrote:

This precisley what happened in my case.
Except instead of a poor joint, the pipe didn't quite make it through the gable wall, and dripped down INSIDE the wall. The problem didn't show up till a combination of lots of hot water at Christmas, and some bloody cold weather, caused the condensation.

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Hi Michael,
If you install a run of waste pipe dead horizontal, it will of course still drain, and you may not notice any problems for some time, however this is not a self cleaning gradient and eventually sediments build up on the bottom of the pipe.
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This is what happened to us. The latest incarnation of the bathroom involved moving the sink from very close to the wall to very far away, ie the other side of the room! I cut exact sized holes in the middle (top to bottom) of 4 joists to get the waste out.
Initially I had the waste *pretty much* dead level, but obviously water collected and stagnated if left for a few days.
The other week I replaced the bath waste with a smart chrome job which involved re-visiting the sink waste too since they ended up next to each other, and I noticed I'd put both wastes one brick too high so water DEFINITELY collected. I took the brick out below the pipe and got a pretty good drainage slope out of it - boy did a lot of stinkin' water come out of it :)
Everything's fine now - no more bad water smells in the bathroom.....
cheers
witchy/binarydinosaurs
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Bad smells arising from laying a waste pipe without a fall may not be due to stagnated water collecting in the pipe. Even if the pipe if full of foul smelling water, the smell shouldn't enter the room if the trap on the appliance is intact.
The smell probably arises from the fact that the integrity of the trap is being compromised by self siphonage due to the waste not being laid with adequate fall.
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I should've added that I still haven't reinstalled the toilet after much umming and ahhing about whether to laminate the floor or not, so the soil pipe only has a safeway bag gaffa taped over it :) Now that we've decided to get the floor sanded I need to think of a way of levelling the bog since the floor slopes enough for the experience to be rather strange!
cheers
witchy/binarydinosaurs
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