mike2016 Posted May 2, 2021 Share Posted May 2, 2021 I purchased a Zehnder MVHR which needs a Condensate drain. It comes with a 32mm weld or 40mm BSP adapter for the bottom of the unit. I was wondering is it possible to reduce part of the run to 22mm using Hep2o or something like that or why it needs such a large outlet, even more than my washing machine?!! Thanks. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted May 2, 2021 Share Posted May 2, 2021 22mm sounds like loads doesn't it but I guess the weld adapter is all about connecting simply into typical waste pipe sizes and if you do have a 22mm run you will still need to wrangle a way to connect that into the waste system somewhere. I think that I am saying perhaps best to stick to waste pipe sizes so you can get adapters, there must be small sized waste pipes out there I think the overflow from our roof tank is about 20mm but 32mm is the most common. 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted May 2, 2021 Share Posted May 2, 2021 Why swap to hep when you can get solvent weld in smaller sizes, standard overflow pipe size, then you are not mixing pipe types. Link to comment Share on other sites More sharing options...
Conor Posted May 2, 2021 Share Posted May 2, 2021 Building regs stipulate min of 22mm diameter for a condensing appliance so I don't see why not. Link to comment Share on other sites More sharing options...
Marvin Posted May 2, 2021 Share Posted May 2, 2021 Think sometimes after a certain distance 32mm is recommended to stop siphoning. But also some appliances have anti-siphoning traps. My MVHR has run fine with 22mm 4m across and 3m down to a 40mm waste for the last 4 years but I'm only moving air for 250m3 building Good luck Marvin Link to comment Share on other sites More sharing options...
mike2016 Posted May 3, 2021 Author Share Posted May 3, 2021 Sounds good! Many Thanks all! Link to comment Share on other sites More sharing options...
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