Author Topic: Basin Waste Direct into Soil Pipe OK?  (Read 1190 times)

Basin Waste Direct into Soil Pipe OK?
« on: March 23, 2019, 02:44:47 pm »
I have a loo with a 110mm soil pipe running horizontally under a small basin, and it would seem obvious to connect the 32mm basin waste to the soil pipe by drilling a suitably-sized hole and solvent welding an appropriate strap boss (as shown in this cheeky video).  It's just a short vertical connection.

Is this allowed (ie legal)?  Might there be any drawbacks, eg flushing the toilet causing too much disturbance in the vertical trap and waste pipe?  The soil pipe connects to a vented vertical stack about 1m to 1.5m away from the basin.

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #1 on: March 23, 2019, 06:08:40 pm »
That’s fine.
We are making a New World (Paul Nash, 1918)

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #2 on: March 23, 2019, 09:22:46 pm »
Well, that was straightforward!  :thumbsup:

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #3 on: March 24, 2019, 05:39:20 am »
Over in Leftpondia  you would need a "trap" between the basin and the soil pipe.  Trap is a u-shaped bend which holds water (when not draining) and thus blocks passage of sewer gases up through the basin.  It is convenient if the trap is assembled with threaded or compression connections, so that it can be removed to clear out accumulations of hair, etc.

The strap boss is a clever thing.  Hadn't seen such before.

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Basin Waste Direct into Soil Pipe OK?
« Reply #4 on: March 24, 2019, 06:24:34 am »
Over in Leftpondia  you would need a "trap" between the basin and the soil pipe.  Trap is a u-shaped bend which holds water (when not draining) and thus blocks passage of sewer gases up through the basin.  It is convenient if the trap is assembled with threaded or compression connections, so that it can be removed to clear out accumulations of hair, etc.

The strap boss is a clever thing.  Hadn't seen such before.

In the UK you have a trap too, fitted directly beneath the basin. 
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #5 on: March 24, 2019, 06:25:09 am »
+1 for a trap; it'll stink to high heaven otherwise


cheers


Re: Basin Waste Direct into Soil Pipe OK?
« Reply #6 on: March 24, 2019, 10:13:50 am »
Thanks.  I should of course have mentioned that there would be a trap!  The basin currently has one of these, but I envisage swapping it for one of these, due to the planned vertical orientation of the pipe, rather than it's current horizontal position.

I suppose the proximity of the vented stack means that there won't be an air/water surge from flushing the loo big enough to disturb the water in the basin trap.

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #7 on: March 24, 2019, 11:08:10 am »
If you are concerned about the possibility of the water in the stack pulling the water out of the trap you can get anti-syphon traps - basically it is a standard trap with a one way air inlet valve on the top of the trap so any suction "downstream" just pulls air in through the valve and not the water out of the trap.

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #8 on: March 24, 2019, 05:07:13 pm »
If you are concerned about the possibility of the water in the stack pulling the water out of the trap you can get anti-syphon traps - basically it is a standard trap with a one way air inlet valve on the top of the trap so any suction "downstream" just pulls air in through the valve and not the water out of the trap.

The waste from the toilet would have to be VERY full to pull vacuum and siphon the basin trap. It’ll be fine without and anti-syphon trap.
We are making a New World (Paul Nash, 1918)

Aunt Maud

  • Le Flâneur.
Re: Basin Waste Direct into Soil Pipe OK?
« Reply #9 on: March 24, 2019, 05:27:39 pm »
Depends on the curry.

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #10 on: March 24, 2019, 06:08:23 pm »
if you have a basic 4" water trap then it will pull air through (and make a gurgling sound) when it sees a pressure differential of about -0.15psi, i.e. not much. I would imagine that this is well within the scope of Bernoulli-induced pressures whilst there is a flow in the soil pipe.

 If the soil pipe is 'filled', even briefly, above the connection to the basin, and there is no suitable vent, pressures in the pipe could become positive, in which case the trap will gurgle and burp stinky gas into you home. Not nice!

Most folk put up with the first gurgle but not the second; it all depends where the vent is I suppose.

cheers

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #11 on: March 24, 2019, 06:19:27 pm »
And an anti-syphon trap would cure that, should it arise?

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #12 on: March 24, 2019, 06:21:53 pm »
the first one but not the second?

cheers

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #13 on: March 24, 2019, 07:00:09 pm »
In the OP it says there's a vented stack downstream of the connection, so it shouldn't happen.
Quote from: tiermat
that's not science, it's semantics.

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #14 on: March 24, 2019, 07:15:41 pm »
In the OP it says there's a vented stack downstream of the connection, so it shouldn't happen.

Exactly.
We are making a New World (Paul Nash, 1918)

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #15 on: March 26, 2019, 05:00:59 am »
I am having a similar install. Approved Drainage regulations H will tell you everything...septic tank effluent treatment with reed beds is interesting..

=https://www.planningportal.co.uk/info/200135/approved_documents/71/part_h_-_drainage_and_waste_disposal&ved=2ahUKEwij2qzHgZ_hAhX7SBUIHWFJBR4QFjAAegQIAxAB&usg=AOvVaw0RDiBYgjCuPwyx_29CiVEg

Re: Basin Waste Direct into Soil Pipe OK?
« Reply #16 on: April 13, 2019, 04:24:40 pm »
All now done, and satisfactory.  It was an interesting little job: