Another SVP query - re downstairs toilet

[GeorgeR]

Hi,

I am replumbing the toilet and hand basin in my downstairs cloakroom, and was hoping that you may be able to give me some advice please, in relation to the soil vent pipe.

If The Scruff is reading this, you may recall giving me some help about this time last year, when I was installing two showers. I got the job done ok, but then spent a week in hospital when I got an injury to my kneecap that went bad. All is well know, and the showers are working fine. I appreciate the help you gave then.

Anyway, my query now is this. We have a downstairs toilet, which connects to its own soil pipe that goes into the floor, and then to the main drain outside. It is completely separate to the system for the upstairs toilets which are on the other side of the house. There was also the waste from a shower next door that fed into this soil pipe, but when we fitted the upstairs shower, we got rid of this and I have stopped that up, so now the toilet is the only thing going into it. It is on a branch that comes out of the side of the soil pipe, and has a run of about 50cm.

When we removed the boxing in the cloakroom, we discovered a soil vent pipe that goes straight up from where the soil pipe comes out of the ground, nearly up to ceiling level, with a funny cap on the end of it that appears to seal the pipe but have some sort of diaphragm in it. Above the end of the pipe, there is a hole cut in the plasterboard of the ceiling, so that the end of the pipe is nearly sticking into the void between upstairs and downstairs.

If we can, what we would like to do is to lower the height of the vent pipe, so that it is low enough that we can hide it in a built in false wall that will hide the cistern, but have a worktop over it at the same height as a basin on the other side of the room.

My questions are, can I reduce the height of the vent pipe down that low, or is there a reason for it having to go so high? And what sort of end piece do I have to put on the end of the pipe. Any other tips or requirements that I should be aware of here?

Sorry if I am showing my ignorance, but you guys were so helpful last time, with such good results that I thought I would try again.

Kind regards, and a Happy New Year to you all.

George R.

[Chris]

The funny thing with a diaphragm is an air admittance valve. Air can get in but not out. You can cut it down (replacing aav)as long as it stays above the flood level if the sewer blocks. Eg does that basin discharge into the wc soil pipe? The aav should be accessible - under a screwed panel is ok.

If you can't cut the 110mm pipe that low, you can change the upper part to 32/40mm which is easier to hide, and put an aav on that.

[thescruff]

Morning GeorgeR,

Nice to see your still trying, Chris just about covered your answer.

The width of a sheet off board is 2.4m so keep the top of the valve just below that, say 2.3m and all should be fine.

Happy New Year George.

scruff

[GeorgeR]

Gents,

Thanks as ever for your helpful advice. I'm 99% certain the basin doesn't go into the same soil pipe. The cloakroom is on the side of the house, and it appears that the basin and the toilet have separate soil pipes. I will double check, though, in the morning to make absolutely sure.

So, your advice gives me what I need to proceed. I can keep the outlet high enough to make sure there are no problems.

Many thanks, once again. You guys do a great job.

Kind regards.

George R.

[thescruff]

Won't make any difference if it is connected to it George provided the vent is above the flood level of the highest sanitary ware