Reading through answers to others' problems on here and the lack of a stack vent on my roof is suggesting to me that my sewage smell coming up the shower drain (and waste pipe in utility )in a number of newly constructed rooms have a problem with or absence of any AAVs, so a few questions please:

Would building control here in england needed to have checked the fitting of any AAVs before passing the plumbing work?

Is there any way that myself or any plumber I get in for a second opinion (to check my own plumber isn't blagging) would be able to check visually or mechanically whether there are AAVs fitted? My problem showers are walk in with WEDI boards, one within floorboards, one in concrete but there is no evidence of any AAv on the utility pipework which is exposed and which has a WC next door to it? Thanks.

They should be able to check after the fact on your system and if an AAV is installed. If you follow the sewer lines around you may be able to see them yourself. Also a smoke test could reveal if they are working or not.

Here is a short video and so you can see what one looks like installed.

Ref:

Air Admittance Valves

Hi hobnob,

Certainly the building and plumbing practices and codes will vary between England and the US. The laws of physics are the same but our ways of contending with them will differ.

Here in the US, these codes are administrated by local governments, therefore codes will vary from place to place. Wet venting is permitted by most but not necessarily all local codes. The use of AAV"s is permitted by some and not others. Where permitted, all require that the AAV be "accessible". Meaning that while it may not be visible, you must be able to get to it with out change or damage to the structure. You could put in inside a wall but there must be a cover panel that can be removed to service or replace it. Therefor, a visual inspection (assuming a reasonably knowledgeable person) could determine its presents.

In the drawing below note that the drain piping for the lavatory connects to the drain for the shower and to the vent pipe for the lavatory. At times it serves as a drain for the lavatory and at other times it serves as a vent for the shower. Note that the vent for the lavatory does not necessarily go through the roof. It can connect to the vent stack in the attic above or even connect back to the stack through the walls as long as it does so above the level of the lavatory.

In attempting to determine the source of sewer gasses and odors, I would first insure that all traps have sufficient water. Slowly pour a small amount of water down each drain. Pour slowly so as to not set up a siphoning action in case you do have a blocked vent. If the odors dissipated, that would indicate that the source of the odor is through a trap. If after normal use of the shower, the odor returns that would indicate a blocked vent pipe or and unventilated shower drain. If the use of the toilet (WC) causes the odors to return, that would indicate a blocked vent stack. A poor seal between the toilet and the drain piping can also allow odors to escape because the trap of the toilet is an integral part of the toilet. In the US, a ring of wax between the piping floor flange and the toilet is used to create that seal.

So a visual inspection by you or a plumber should confirm or eliminate the presents of AAV's. If AAV are found, they should be checked to insure that they are functioning properly. The use of AAV's is not the preferred way of venting and should only be used when no other method is practical. Vent piping may be concealed in the walls and not necessarily go through the roof. Try to specifically locate the source of the odors before trying to take corrective action.