No offence taken. In my experience my method would not cause a problem as the standpipe outlet is already so close to the soilpipe boss and I would not expect the standpipe itself to ever be full of water and it's trap is below the other 2 outlets. Plus unlikely that a full sink and a full basin both discharging at the same time! But I do take your point, and my method, although expedient probably contravenes the regs if I could be bothered to look it up. Just thought it would be easier for a DIYer to do. If I was doing it then it would be a new soilpipe boss but I felt the OP needed something a bit simpler for DIY. Cheers and Happy Sunday!
Hello again Julie Street,
Thanks very much for your reply - I am glad to read that You were not offended by my remarks at the beginning of my first reply to you.
I don`t want to labour the point but I could never agree that it is appropriate to have 3 x 1.5" Waste pipes joined together and discharging from a 1.5" pipe.
I cannot agree that it would not be possible for the vertical Waste pipe to be full of water and I know that IF these 2 waste pipes are - Kitchen Sink and a Basin the wastes could easily and often be discharging together.
When for example a full Kitchen sink discharges water fills a 1.5" waste pipe to Full bore and from experience of timing the discharge from a 12 Litre capacity bowl it takes about 25 seconds - 25 seconds during which the vertical waste pipe in this case would be full of water even at the low point where you suggested a tee for a Standpipe would be.
That is without taking into consideration waste water from perhaps a Basin discharging at the same time adding a few more seconds to the situation.
As We know although the waste water from a Washing Machine is pumped into a Standpipe it is only discharging past the Trap by gravity / displacement.
Because of that there is very little impetus [if any ?] on that water to enable it to overcome the downward force of water in the vertical waste pipe and enter the discharging column of water flow.
I do feel that it would be possible for the vertical waste pipe to be `Full` while one or more other wastes are discharging and that would cause the water in the Standpipe to possibly overflow.
Even if we suggest that people usually use a plastic bowl in a Kitchen Sink or might have a smaller capacity Sink so it does not discharge as much as 12 Litres - they would probably still hold 9 or 10 litres of water so the vertical waste pipe would still be full for 18 or 20 seconds with just the Kitchen Sink discharge.
I do understand your motive of trying to explain the easiest way for the OP but if they and others followed that method and the circumstances that I explained did occur with plenty of water discharged out of the Standpipe they would not be grateful then.
Thanks for stating that if You were doing the job you would connect a Standpipe using a new Boss on the Soil pipe.
With regard to your comments about whether there is anything `in the Regulations` about combining waste pipes - as Ric2013 has correctly stated you would not find anything specific in Part H of the Building Regulations - `H1 Drainage & Waste disposal`.
As with most of the Building Regulations
they do not actually instruct on HOW to do things or what can and cannot be done in practical / easy to understand terms.
However if a Plumber / Builder ever tried to get 3 x 1.5" Waste pipes connected together and discharging into a Soil pipe via a 1.5" Boss approved by a Building Control Officer they would very quickly find out that it would NOT be approved / passed !
Thanks again for your message.
Chris