Location of discharge pipe on unvented cylinder


Distinguished Member
I posted a year or so back about the total messed up install I had of an unvented system. I can finally get this resolved. I’m having the cylinder moved from the loft into the airing cupboard. At present the discharge pipe runs down the outside side of the house from the loft.

Due to the move the discharge pipe would need to be run down the front of the house which I’m not happy with. So the installers say the pipe can be fed into the waste pipe under the bath.

Is this ok to do? I don’t want to replace one major problem with another. Does all the waste pipe need changing to heatproof? Also I see online it keeps mentioning the soil stack when doing this. Some bright spark before I moved in cut off the soil stack in the loft. There are valves on each toilet but the en-suite smells with shower badly now an again. I have read the correct tundish needs to be fitted to stop smells also from the waste.

Does the soil stack also need sorting out?


Distinguished Member
Unvented DHW - DIYWiki is probably a reliable source of the information you need.

My en-suite shower trap (shallow) smells from time to time - but from a build up of slimy soap/detergent gunk in/on the component parts. It's not from the sewers. A good clean will cure until next time swmbo complains.

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