Green Building Forum - bathroom waste venting Mon, 17 Aug 2026 02:31:20 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280511#Comment_280511 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280511#Comment_280511 Sat, 16 May 2020 14:59:01 +0100 mitchino
In the new layout there will be a single sink, a shower, a bath and WC. What I want to know is, do I have to have the additional vertical air vent?]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280512#Comment_280512 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280512#Comment_280512 Sat, 16 May 2020 15:19:36 +0100 Peter_in_Hungary bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280514#Comment_280514 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280514#Comment_280514 Sat, 16 May 2020 15:41:12 +0100 djh bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280515#Comment_280515 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280515#Comment_280515 Sat, 16 May 2020 16:09:22 +0100 philedge bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280518#Comment_280518 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280518#Comment_280518 Sat, 16 May 2020 17:41:10 +0100 mitchino
My new layout would have the shower furthest from the main stack, where the bath use to be. The bath would be above the branching 110mm pipe and would have a short connection to it.

Thanks for info re air admittance valves, I didn't know such things existed. I always wondered why modern houses never seem to have pipes poking out the roof.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280524#Comment_280524 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280524#Comment_280524 Sat, 16 May 2020 19:31:42 +0100 Peter_in_Hungary Posted By: Peter_in_Hungarythen install an automatic air vent (= a plastic fitting that has a one way rubber diaphram in it).


Posted By: mitchinoair admittance valves,

Yes that's it - I'd forgotten what they were called:sad:]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280544#Comment_280544 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280544#Comment_280544 Sun, 17 May 2020 15:39:57 +0100 Mike1 Posted By: mitchinoThanks for info re air admittance valves, I didn't know such things existed. I always wondered why modern houses never seem to have pipes poking out the roof.
That's not necessarily the reason. It is still necessary for some soil pipes to end in vents (to prevent a build up of explosive gases in the sewers - air admittance vales only allow air in, not out) but these days they mostly terminate in roof tile vents, rather than with pipes that project above the roof.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280547#Comment_280547 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280547#Comment_280547 Sun, 17 May 2020 17:53:23 +0100 djh Posted By: Mike1That's not necessarily the reason. It is still necessary for some soil pipes to end in vents
That's true, but it's not required that every house has one. In a development of several/few houses, it is permitted to only put an SVP on the house at the end of the run and rely on AAVs in the other houses. Developers are tempted because it reduces their costs a little bit.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280578#Comment_280578 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280578#Comment_280578 Mon, 18 May 2020 16:58:05 +0100 goodevans bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280579#Comment_280579 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280579#Comment_280579 Mon, 18 May 2020 17:27:49 +0100 djh Posted By: goodevansand the vent pipe doesn't even need to go on the house - I have one shared between two houses on a garage and it looks like it's a gutter down pipe - unless you look up (it's a dry stack and therefore only needs to be 75mm)
That's true, ours is on the house but is designed to look like one of the downpipes.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280683#Comment_280683 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280683#Comment_280683 Fri, 22 May 2020 19:30:23 +0100 revor I have recently done a downstairs WC and cloakroom and space in the cabinets would not allow me to fit a 110 0r 80 mm AAV. So I fitted an AA basin trap and a 40 mm AAV on an extension piece behind the cloak cabinets. I was informed it would not work as when the toilet was flushed the AAV had to allow the same volume of air as the water. However when I ran some trials there was no issue. Thinking about it the air flow into the system will move faster than water out of the WC which is why I reckon it works.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280684#Comment_280684 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280684#Comment_280684 Fri, 22 May 2020 20:42:36 +0100 djh Posted By: revorI was not aware that SVP could be shared amongst houses.
It isn't generally but can be on estate developments, AFAIK.]]> bathroom waste venting https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280692#Comment_280692 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16554&Focus=280692#Comment_280692 Sat, 23 May 2020 11:10:30 +0100 goodevans
There are two reasons for venting as far as I'm aware:
A) the release of gasses in the pipes (to prevent pressure build up, explosive gases, harmful gasses).
B) to cope with flood situations in downstream sewers (aka surcharging) - as the water backs up into 'your' local branch (one or more houses) you must allow the air to escape.]]>