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Anti vac trap or air admittance valve

Discussion in 'Plumbing and Central Heating' started by Fredstudio, 3 Mar 2021.

  1. Fredstudio

    Fredstudio

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    What is the benefit of fitting say a 40mm or 50mm air admittance valve. As apposed to an anti vac trap at the appliance? Thanks
     
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  3. Madrab

    Madrab

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    Depends on what's on the waste run, if it's just a sink then nothing else needed than an anti vac trap as you're only venting that trap using its small vent.
    If there's more on the run than say 1 trapt - appliances etc, then you really want to vent the run. A 40>50mm AAV has a larger larger vent so is able to support more than one trap/outlet at a time. Even then though, supplementary venting is more applicable when there are longer runs with bends and multiple wastes feeding in, shorter lengths shouldn't really need it
     
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