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Plumberpro, Plumber
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Experience:  Heating and plumbing answers. 20 years experience
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I'm in the process of changing out pipework running from the

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I'm in the process of changing out pipework running from the groundfloor toilet to the main drain (110mm pipe). Main reason for this is to reclaim an adjacent fireplace through which the old waste/soil pipe ran to the cess pit outside, with the chimney being used to contain/hide a vent pipe.
Question is - with the distance between toilet and entry to main drain being app 6 feet - do I need to put a vent pipe in? If so, and I presume I should, what size pipe should I use? 110mm pipe running up the outside of this single storey highland cottage might look a bit OTT so could I get away with a smaller diameter pipe? if so, what size?
Second part to this question is 'positioning' of the vent. On the same level but upstream of the toilet I intend to plumb in a shower and a wash hand have a 110mm socket plug with a 110x40mm boss adaptor for this purpose. If I could put a vent in between the toilet and the shower I could utilise an alcove to take the vent pipe up the inside of it, five or six feet, then penetrate the wall to the outside and put in a ventilation cap there... Could a smaller diameter pipe (40mm) be used for a vent pipe?

Hi, you can terminate a vent above the level of the highest appliance waste,ie sink. As long as it is a metre away from air vents and Windows it can be terminated anywhere above your highest soil connection. If you have room internally then you can run a small section of 110mm up above the sink then add a 110mm air admittance valve. This does the same as a vent(allowing air in so the fluids move away quickly) but only allow air in and not out to prevent soil smells coming back into the could get away with 3 inch vent pipe with 3 inch air admittance valve.but I would try to keep it 110mm(4 inch) to ensure the best running of fluids away.

The vent can be put between the toilet and shower , but I wouldn't run it off the shower waste ,you might be forever unblocking the loo,

Customer: replied 1 year ago.
you'd recommend running a different waste pipe from the shower/wash hand basin to the main drain, avoiding toilet pipe altogether?

No, I meant don't take the vent off that 40mm waste pipe. Its fine to run the shower and sinks etc into the 110mm pipe, but try to take the vent off the 110mm pipe as close to the toilet connection as possible.

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Customer: replied 1 year ago.
Ok....understood.Thank you!

Your welcome. All the best