Is this acceptable. Foul drain. Swift replies needed

[2021bela]

Hello, my question is will this be acceptable.

Here I have 2 rooms beside each other but need a toilet in both on the ground floor before 150mm insulation and 75mm screed get installed. One room is a bathroom, the other an ensuite. The toilet in the left will have a 90 bend under it and will be going into a 110mm pipe with a fall of 1/40 or slightly less. It will have a tee on it just before it leaves the exterior wall and will connected to another toilet above. Both pipes will be 150mm of the wall from the furthest part of the pipe. Once the pipe leaves the house it will have 2 x 90s which will be connected to an inspection chamber which will be connected to a septic tank with a 1/40 fall in the pipe.

In the toilet on the left it will have an air admittance valve to stop any back suction from the other toilet.

The bathroom with the exterior wall will be 2.4m wide. Enough to get the 1/40 fall needed for the waste water to get away without any issues.

Originally there was only supposed to be one toilet but now another needs added in the small box room on the left.

I could have an option of a saniflow toilet in left room but what I describe above would be my preferred option.


Another question I have about the rain water drainage. I have a run of 22m and the underground pipe will be 10inch black corri pipe. What would be the minimum fall I can get away with if the underground with this pipe. Can I go shallower that 1/110.

First fix going in in the next few days and all swift replies will be much appreciated. TY.

 

[2021bela]

 

[oz-plumber]

You can't run a toilet into a 'T' fitting.
You need a 45 degree junction and a 45 degree bend to make it 90 degrees

 

[exedon2]

Better still bring both out separately into a new chamber the two 90 bends not a great idea either.
If the top one is above is above finish ground level use a soil pipe junction with access plug in top to give rodding access.

 

[2021bela]

You can't run a toilet into a 'T' fitting.
You need a 45 degree junction and a 45 degree bend to make it 90 degrees

What about a sweeping tee?

I can't visulise what you mean by a 45 junction and a 45 bend to make a 90?

 

[ShaunCorbs]

Looks fine to me but I would vent it either durgo or external

30mm fall pm

 

[2021bela]

There will be a vent pipe coming of the inspection chamber.

My main worries are having issues with the tee. Would it flush away ok or can it block seeing it's a tee.

 

[exedon2]

You should probably read building regs document H section 2
2.49 deal with access points

 

[2021bela]

You should probably read building regs document H section 2
2.49 deal with access points

I will do this now. Thank you

 

[2021bela]

Would a saniflow not just save all the hasle with this. A saniflow toilet in that room, 1&12 pipe to outside with the connection to put in the small section of 110mm pipe I have between the 2 bends (1 leaving the house, the other going to the inspection chamber)

 

[ShaunCorbs]

What issue with the tee it would only block to two reasons incorrect fall / wrong object going down there

 

[2021bela]

What issue with the tee it would only block to two reasons incorrect fall / wrong object going down there

I would say I'm wrong but I have it in my head because it's a lush, somehow/maybe it wouldn't fall away as is because it has more surface area in the intitonal flush and could somehow force some back.

 

[exedon2]

Can I ask why the need for double bend arrangement you have shown is it to get to correctly invert?

 

[2021bela]

Can I ask why the need for double bend arrangement you have shown is it to get to correctly invert?

There is a window above the bends and can't continue it on up for vent pipe. I have lived in a house for 20 years that has a double bend leaving the house and never any issues.

 

[ShaunCorbs]

I would say I'm wrong but I have it in my head because it's a lush, somehow/maybe it wouldn't fall away as is because it has more surface area in the intitonal flush and could somehow force some back.

😀 it’s not travelling that fast

 

[2021bela]

😀 it’s not travelling that fast

Lol 😂

 

[2021bela]

My 3 options are.

Both toilets to have there own pipes through the insulation and screed.

Saniflow in small toilet room with 1&1/2 pipe through the floor out the wall near the 4inch leaving the wall.

The last option is what I have in the diagram. 4 inch pipe feeding both with correct fall and an air admittance valve on toilet in the small room.


My first option there will be alot of messing with insulation and doing something to help keep the fall from not sagging. Plus that's alot of void together under sand and cement screed.

The sani flow seem the simplest of the two however tieing it into the 4inch might be an issue outside. Is it possible to connect into the bend of a 90 or does it have to be on the straight part of the pipe.

Option 3 is simple enough but I'm afraid of any issues of blocking at the sweeping tee! This is my main concern because if it does block, it's alot of work to rectify it.

I have asked 3 plumbers s I know, and all 3 have different opinions about above. This is why I'm scratching my head still undecided what one to do.

 

[ShaunCorbs]

I wouldn’t fit a sani unless you really have too

 

[2021bela]

I wouldn’t fit a sani unless you really have too

Why's this

 

[ShaunCorbs]

Why's this

Nothing is better than main drainage you can get problems with sani also not many people like to work on them after

 

[2021bela]

Nothing is better than main drainage you can get problems with sani also not many people like to work on them after

Would you say option in the OP is better method??

 

[ShaunCorbs]

Yes much better and most commercial buildings / schools are like this 3-4 toilets in a row just use swept fittings which underground normally only come in

 

[2021bela]

Yes much better and most commercial buildings / schools are like this 3-4 toilets in a row just use swept fittings which underground normally only come in

If I do go with the first option. Just to clarify, isn't it 150mm off the wall to the furthest point on the tee away from the wall coming up through the screed

 

[ShaunCorbs]

Normally 16” from a wall l-r

 

[2021bela]

Normally 16” from a wall l-r

16 cms? Is that before or after tiling.

 

[gpbeck]

16” is 40cm

 

[2021bela]

16” is 40cm

I know this, I was thinking he made an error. That's why I tried to correct him in a nice way 🥴😂

We must be getting our wires crossed because the pipe coming off the wall from the exterior can not be 400mm of the wall from the back of the toilet. If it was 400mm that would be near the centre of the toilet. I've always believed the pipe coming up there the floor was 150-160mm for the bend at the back of the toilet to drop into without any issues. He must be coming of the wall left or right although he did mention this 🥴. My measurements is from front to back and is always 150-160mm

 

[ShaunCorbs]

Left to right not front to bad toilets need to be approximately 16” centre line of a parallel wall

Off the wall eg front to back or in and out depends on the toilet but 105mm centre

 

[2021bela]

Left to right not front to bad toilets need to be approximately 16” centre line of a parallel wall

Off the wall eg front to back or in and out depends on the toilet but 105mm centre

Yes that makes sense. I always measure the double color furthest away from the wall which is 160mm .