This document gives prescriptive information:
Approved Document G
Frequently Asked Questions
https://assets.publishing.service.g...chment_data/file/509352/160321_Part_G_FAQ.pdf
Paragraph 3.60 of the Approved Document says that if a discharge pipe is connected to a soil stack the discharge pipe should be either polybutalene or cross linked 8 polyethylene. Does this mean a polypropylene discharge pipe cannot be used?
As stated in its Introduction section, the guidance in the Approved Document is intended to provide advice on how to comply with the requirements set out in the Building Regulations and that “there may well be other ways of achieving compliance with the requirements”. The Department’s view is that it would be acceptable, subject to also complying with sub-paragraphs a, b and d of 3.60, for these pipes to be polypropylene to BS EN 1451-1, as recommended in BRE Information Paper 8/07.
Paragraph 3.60 of the Approved Document allows safety relief discharge pipes to connect to a soil stack if it can safely resist the temperature of the water discharged. Which materials are considered to be suitable?
Metal pipework, such as cast iron, is suitable. For smaller hot water systems, BRE Information Paper 8/07 indicates that discharges can be made to PVCu stacks, provided that: relief discharge is from domestic unvented hot water storage systems only – not combi boilers or sealed system boilers. storage volumes do not exceed about 210 litres. stacks are fully ventilated (ie. no stack cap or air admittance valve). pipework complies with BS EN 1329-1:2000 or BS 4514:2001.
So although I have drainage soil pipes to BS4514, the above states:
not combi boilers or sealed system boilers. storage volumes do not exceed about 210 litres.
I have a 250 litre tank on an unvented system (sealed system) - so quess the answer is no, I can't connect to the PVCu plastic soil pipe under the floor.
So taking the discharge pipe outside, solves part of the problem, but its still discharging to a 'plastic' gully ... if a number of metres away.
A call to Floplast suggests that the run of discharge pipe (in copper) and it being an external gully, it should be ok.
Floplast also commented on discharging to uPVC soil pipes - stating that hot water even at 50-60 degrees - their plastic soil pipes will start to deform, at 200 degrees it will actually melt ... so either way - least you would get would be a drooping Soil pipe on a horizontal run, which obviously this would be a problem.
Still unsure if in the context of undergroung drainage pipes, the 'u' in 'uPVC' (or could be PVC-U) refers to 'underground' or 'unplasticised' ?
EN 1401 suggests it is 'U' for 'underground', yet BS EN 12608 (plastic window profiles) suggests it is 'unplasticised'.