I need to break into the main 4" vertical waste pipe in my loo, in order to reduce it to 1.5" for venting up to the roof, as from about
12" above floor level. The huge vertical box section which the builders installed seems so ugly and unnecessary.
How can I break apart the seal in the grey pipe, I wonder? It's solvent joined isn't it? The pipe was installed in the mid-80s and is marked Marley Extrusions 110mm.
Are there any building regulations which could threaten my plan? I assume a 1.5" pipe is adequate for letting a few bubbles of gas escape, and should also cope with water rising part way up the 1.5" pipe, e.g. when I drain the bath.
Will I need respiratory gear when I crack into the pipe?!
I don't think you can reduce the pipe diameter to that extent. Maybe to 75mm at most. BTW it doesn't let gas out, it lets air in. You could fit an air admittance valve instead but that must be higher than the highest outlet or overflow feeding the stack.
Thank you for your input. Does it really take more than a 1.5" vent pipe to provide enough air admittance? I only have one vent pipe in the house. Do UK building regulations specify the vent pipe size -
110mm at present - which I see as taking up too much room space.
The vent pipe has to ensure that when the soil pipe/drain is full of water (etc) after a loo flush that none of the water traps on the circuit get emptied eg the vacuum cannot be more than a few mm of water say 0.01 atmospheres. If the vent is 110mm then this will definately work ok hence the BI preference
I had a similar situation in 1983 ago and fitted a 50mm vent pipe.The building inspector was not happy but admitted that (then) the law did not allow him to enforce 110mm. Regs may well have changed by now.
Very helpful information, thank you. The other issue I have is how to break the (solvent? bond into the grey Marley 110mm pipe. Does anyone know if these bonds can be proken, or whether you have to cut the pipe?
Are you sure that it is a solvent weld and not a push fit with rubber seal? Most soil pipe systems are made this way and are assembled using silicone grease as a lubricant or at a pinch, washing-up liquid.
If it really is solvent welded and done properly, then the joint will be pretty much as good as the rest of the plastic, so you probably won't be able to separate it without breaking the fitting and/or the pipe. This is especially true when working in a confined space.
The easiest solution is to cut through the pipe and remake the section using push fit collars. You might have to disassemble a section of the stack to do this but the fittings and pipe are relatively cheap and this will be the fastest way.
On Sun, 05 Oct 2003 14:42:14 +0100, a particular chimpanzee named Bob Minchin randomly hit the keyboard and produced:
From Approved Doc 'H': "Sizes of stack ventilation pipes ? stack ventilation pipes (the dry part above the highest branch) may be reduced in size in one and two storey houses, but should be not less than 75mm".
Ok. Found it. 75mm is allowable on 1 or 2 storey buildinsg, and you CAN use an air valve IF the sewer itself is vented elsewhere. I.e. there MUST be a way to allow gas pressure build up in the pipes to 'blow off' but it doesn't HAVE to be part of the internal sewage system. I have seen 4" pipes stuck over septic tanks going up 20 feet to do this.
I'd advise a 3" pipe that should terminate not less than 900mm (regulation) above the highest window lintel. In practice this is usually stuck up through the roof somewhere, or taken outside and pushed up past the eaves. I actually have mine going through a gable end but beware, when you run hot baths in winter, steam condenses and may drip down a pipe that isn't run consistently uphill - I made this mistake and got a wet wall. May have to relocate that yet.
You original problem of largish box sections in the house to hide the 110mm pipes is shared by most of the 1980s houses where I live. Some have recently gone to the trouble of having the stacks put outside the house which looks ugly in a different way. I note that the stacks are still 110mm grey plastic all the way up. I would imagine yours is solvent welded which can't be broken. You will have to saw through the stack if you want to break into it.
Thank you everyone for your incredibly helpful responses. I checked the Marley fittings after Andy's comments and he was right - some of the key joints do appear to be push-fit, which should make the job much easier. BillR's observations about 100mm pipe being kicked outside many houses is also useful information, i.e. on folks' rejection of internal box eyesores. Why did builders do such a botch job, at least in the 1980s? In the USA I gather they hide the pipes in the walls.
The official regulation pipe size pointed to by Hugo and The Natural Philosopher is exactly the information I needed, whether or not I follow it! Thank you. Is this the sort of thing a prospective buyer's building society surveyor would notice if I come to sell the house? A box section will remain in the kitchen, directly below the section I'm seeking to remove upstairs, so would he be smart enough to notice that there's not a box section above? I will take the 1.5" pipe back to
110mm the moment it enters the loft.
It's hard to believe that a 1.5" pipe wouldn't allow sufficient air flow to prevent a vacuum, and should certainly let out the occasional bubble of gas. The point about condensation has also made me think twice. I was about to take the 110mm pipe down to 1.5", then go through two 90 degree bends in order to run the 1.5" pipe vertically in between a partition wall, or between the outside wall/fibreglass/plastic sheet and the internal plaster board. If The Natural Philosoper is right, the short horizontal section might cause damp problems for a start. But wouldn't I already have condensation as the bath and basin pipes run horizontally for several metres to the waste stack? I may need to test the re-engineered system before sealing it all up behind tiles. I don't relish the stench when I break into that pipe.
The whole point of having the stack inside the house is so that it does not freeze up in winter. Using a blow lamp to thaw out an external 110 plastic stack is not on.
AFAIK, only every 4th or 5th house requires a full opened stack. All the rest can have an air admittance valve or HepVO tarps on all waste water appliances.
Plastic pipes for outside have improved somewhat from the the original
1950/60s stuff. The problem was that the plastic fractured over time from below freezing to exposed high summer temps (sun directly on the pipes) . Freezing should not be a problem as water will not freeze in a 10-15 foot drop int the underground (warmer) pipes. Outside stacks that freeze tend to be incorrectly installed in some way.
On Fri, 17 Oct 2003 23:53:09 +0100, a particular chimpanzee named Andrew randomly hit the keyboard and produced:
How can a soil stack freeze up in winter? Unless it's not ventilated and is filled up with water due to a blockage, then freezing will not be a problem. If either of those conditions apply, then you have a problem with it at any time of year.
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