Kilt Posted February 20, 2021 Share Posted February 20, 2021 I know there another AAV topic running, but I didn’t want to muddy the waters, by jumping on that topic. renovating a bathroom, and there was a 110mm AAV literally jammed in against concealed cistern. Cistern has been replaced and rather than repeating a shit job and jamming AAV back in, I’ve lowered AAV to sit nicely underneath. However, would it be best to leave a 110 lower, or would a 2”/50mm AAV, up past the cistern height be better? It’s one toilet and basin on this leg/branch, leading to the main stack (vented to roof). Theres another branch/leg feeding main stack, but this branch is also vented to roof. so there’s argument, no AAV is needed at all. My major concern is potential backwash/splash up the bend to the lowered AAV. Link to comment Share on other sites More sharing options...
Kilt Posted February 20, 2021 Author Share Posted February 20, 2021 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 20, 2021 Share Posted February 20, 2021 (edited) Get rid of the AAV's, as they've been fitted in error. Immediate horizontal run = instant air-break, so really not necessary at all. If you install 2x 50mm AAV's then each need to go back to 110mm pipe bosses on individual 50mm pipe runs. You cannot fit 2 on a single stem of 50mm pipe, only 1. Edited February 20, 2021 by Nickfromwales Link to comment Share on other sites More sharing options...
Kilt Posted February 20, 2021 Author Share Posted February 20, 2021 48 minutes ago, Nickfromwales said: Get rid of the AAV's, as they've been fitted in error. Immediate horizontal run = instant air-break, so really not necessary at all. If you install 2x 50mm AAV's then each need to go back to 110mm pipe bosses on individual 50mm pipe runs. You cannot fit 2 on a single stem of 50mm pipe, only 1. Interesting, I’ve had a chat with a few people and seems to be split on whether AAV is needed or not, however no-ones mentioned the horizontal air break. Thanks. I was originally just thinking of just going with the one 50mm (2”) AAV. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 20, 2021 Share Posted February 20, 2021 58 minutes ago, Kilt said: Interesting, I’ve had a chat with a few people and seems to be split on whether AAV is needed or not, however no-ones mentioned the horizontal air break. Thanks. I was originally just thinking of just going with the one 50mm (2”) AAV. If there is a vertical drop with an open vent to atmosphere, and the two WC’s have horizontal runs to the vertically rising SVP then AAV’s are absolutely not needed. The air break in the 110mm horizontal pipe is all the air admittance you’ll ever need, and more. Link to comment Share on other sites More sharing options...
Kilt Posted February 20, 2021 Author Share Posted February 20, 2021 3 hours ago, Nickfromwales said: If there is a vertical drop with an open vent to atmosphere, and the two WC’s have horizontal runs to the vertically rising SVP then AAV’s are absolutely not needed. The air break in the 110mm horizontal pipe is all the air admittance you’ll ever need, and more. It’d be fab to get rid of it, as during heavy storms we get a wee bit of chatter, with AAV dancing with the wind over the two SVP’s. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 20, 2021 Share Posted February 20, 2021 1 hour ago, Kilt said: It’d be fab to get rid of it, as during heavy storms we get a wee bit of chatter, with AAV dancing with the wind over the two SVP’s. Consider it gone ? Link to comment Share on other sites More sharing options...
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