I have a house on 3 levels – cellar, ground-floor living area and upstairs loft conversion with 2 guest rooms. There is a W.C. on the ground floor but not upstairs, which only had a basin and shower. I have bought an Ideal Standard W.C. and was advised that it didn't matter if I got one with a vertical soil pipe exit or a side exit. I bought the vertical pipe exit model, but I am now wondering if this was a bad choice! I attach a diagram of the layout. Unfortunately it is not possible to site the new W.C. directly above the existing one, which would have been the best solution. All the existing soil pipe run is in 100mm plastic solvent-weld pipe. Because of the way the walls and floor joists run, I will need to pass the soil pipe through the upstairs floor, across the ceiling for about 2.9 metres, then down to join into the existing soil pipe. I believe I will need to ensure there is at least 12cm fall on the horizontal part of the pipe run (Maguire's Rule). I will put up a false ceiling in the corridor space and W.C. to conceal the pipe. The existing soil pipe terminates at the W.C. end with a swept tee with a screw inspection cap, but apparently no vent. My question is, do I need to make provision for venting and/or new points for rodding in the new pipework, and if so, what would be the best way to do this to avoid any blockage or back-syphoning problems in future?
yes you will need a vent otherwise the trap will get sucked out of the higher toilet and cause smelling of foul waste, the outlet type you choice is a good choose because you can pan connectors to go either way, I'd go straight out into that void behind the toilet and in the corner use a juntion ( 4 inch tee) to go down with a lenght going up though the roof and venting outside
There is no void behind the toilet! It is a bedroom, and I cannot convert it into a bathroom because of the way the gable-end window and roof line are positioned. That is why the drawing shows the new W.C. to the right of the existing one. I guess I could run a vent pipe through the roof, but that would mean cutting 2 holes in the floor so that the soil pipe for the W.C. can go downwards out of the porcelain, then with some kind of elbow so that another pipe can come back up next to the W.C. and vertically through the roof. THAT is why I say I think I made a bad choice with the W.C., because with a pan with an exit hole in the side I could simply have used a swept tee. The one I have means that the pan has to sit on the top of the pipe. The joists run the 'wrong' way to allow the pipe to pass through the floor void and the upper floor is sheets of particleboard and the upstairs partition walls are sitting on them, so access is difficult without breaking the downstairs ceilings. In a chapel conversion I once owned the W.C. vent cap upstairs was actually sited in the bathroom next to the pan, and it did not cause any foul smells. Perhaps that is a solution? If I do have to run a vent through the roof, does it have to be 100mm or would a smaller diameter pipe work? Thanks.
Hi Mel, I am not a plumber but could you not reposition the toilet so that the pipe drops down through the floor against the ground floor kitchen wall (corridor side) and into the cellar at that point. I do not know whether you need to hide the pipe in the cellar but it seems to me its not much further to go to connect into the corner soil pipe and would be easier and perhaps give you the fall needed. I do not know whether this arrangement would remove the need for venting and I do appreciate that you need to get through the concrete floor but that might be less trouble than through the floor upstairs, the ceiling and then the roof. There may well be an easier solution with the vents and I am sure you will start getting some suggestions that will help. Good luck with the project .
You haven't supplied enough detail to be given a complete solution, you really need to be on site to see all the permutations. However, I would make the following observations: you have bought the correct pan, the horizontal outlet gives you all the flexibility you need using various pan connectors; as Tom said, yes you need a vent. This could be an air admittance valve to save going through the roof or you could go down to 3" as a vent through the roof (but hey a hole's a hole innit 3", 4" what's in it innit?). Have you thought about the Devil's work aka Saniflo? And you definitely can't run the pipework externally?
if you're thinking of using an air admittance valve it must be higher than the highest waste outlet level, which is usually the wash hand basin,
(1) The toilet pan I have bought has a vertical outlet, NOT a horizontal one. http://www.plumbcenter.co.uk/en/bat...0-close-coupled-vertical-output-wc-pan-white/ (2) I thought about it, but I am in an area which is susceptible to power cuts in winter, for one thing, so decided to try a conventional W.C. if at all possible, which I was told it was. (3) No, I can't run the pipework externally. The waste pipework for the wash basins and baths is separate but does eventually join into the soil pipe at about 5 feet off the ground in the cellar. That being the case, is there still a risk of back flow from the upstairs W.C. if the air inlet valve is lower than the top of the wash hand basin upstairs? rd1, your suggestion regarding making another hole through the concrete floor is worth considering and it would indeed avoid running the pipe across the ceiling of the ground floor, but I would still end up with a horizontal run in the cellar and would still end up having to tee into the soil pipe at some point just inside the garage door, so I am not sure what real benefit that would give me, apart from possibly not having to disturb the swept tee and rodding eye in the existing W.C., which could be a bit tricky.
Mel, My thinking for the alternative route was to see if it would work without needing a vent for the second WC, as it was coming in below the existing WC rather than joining above the existing one. I was unsure whether you would need a vent but it is interesting that you have the bath and sinks coming in at the lower level ( the same as I suggest for the WC) and they do not appear to be vented. I do not understand why the same principle would not apply to the route I suggest but it needs one of the experienced people on here to help you out on that score.
Thanks rd1. I get your point now. I hope, as you say, one of the more experienced people will be able to chip in as well.
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