Soil pipe advice please

Any advice would be good.

I’m proposing to fit upstair 2 bath rooms, 1 en suite, 1 family bathroom. The rooms will be next to each other.

Can I plumb the two toilets into the same soil pipe?

That soil pipe will be running for about 3-4m from the first loo with an approx’ drop of about 1 in 80 (could go to 1 in 60)then through a 90* bend to a further pipe run of approx 4m with a drop between 1 in 40 and 1 in 80 before reaching the vertical drop of the soil vent stack.

Do I need to put the vent stack at the beginning of the run rather than the middle?

I am trying to avoid having to knock wholes in the exterior wall by using an existing opening, as the wall is about 2’6" wide and stone, then digging out 5m trench through concrete floor to lay the pipe before it gets out side.

Any thoughts ideas would be greatly appreciated.


Thanks for the reply, Scott!

If installed & used properly, there should be no problems. Vent pipe & fan take any smells away.

I am very interested in these. But someone said to me recently -- Oh but they smell. Is this true?

I have two going into one… sorry the rest I don’t know,…

I should learn to look at the dates on these posts before offering my little gems of wisdom, I might see that some of them are well out of date! sorry I am sure you plumbing is up and running smoothly by now and if it isn’t my in-put surely won’t help!

This is great, I had no idea that this would turn into such an intersting discussion. Thank you Scott and Jeanette for your composting input. As I mentioned in a previous reply the biolet isn’t going to be part of this project but could be included in the future, I am also going to pass this info on to a friend of mine in the UK who lives in a yurt(spelling??), everytime he meets a nice girl everything goes well until he takes her back to his and she discovers the lack of plumbing. This little baby could revolutionise his love life (certainly help it on to a more even keal anyway).So boilet and potential aphrodisiac!!

Thanks for the info Scott, these units will replace flushable toilets in a few years I imagine, these first generation ones are pretty ugly though, hopefully we will see some improvements to the design.

call her old fashioned but I can’t see my missis going for one of those

This is one of my favourite threads :smiley:

The only maintenance is to add a handful of hummus(compost) to the loo after a`solid deposit’ and then empty the compost tray when full which depends on usage. This goes into a compost bin(for non-edible plants). Poo shrinks to only 10% of it’s wet mass when dried and the loos operate in this way, thus the compost drawer doesn’t fill up too quickly.

Scott, how much maintenance do they require?

Ok but the big benefits with the dry loo is no water to install & pay for, no soil pipes to fit or buy, no digging up floors or drilling walls & on a new installation no septic tank provided you handle your own grey water!
These loos are just a box with a 40mm roof vent done!
Best of luck

Thanks Scott, that’s a bit pricey for the two loo’s on this project but certainly worth considering in the future.

There are a few different models in the Biolet range but they start at around 600Euro upwards. Also known as dry toilets due to no water needed. In Sweden now I believe that all new builds must have a dry toilet as sewage plants cost so much to maintain!

Thanks Andy, have looked at the regs, and as I understand it from table 2;
Max’ length of branch pipe = 15m
Gradient limits of 18mm-90mm per m unless you have more than 1 WC then the gradient may be reduced down to 9mm per m.
As for the elbow it would have the largest radius possible for 90* and the bath and shower feed would also join at the top of the elbow with the two sinks joining the soil pipe where they stand.
It has been suggested that I use a Durgo air admittance valve instead of the standard vent stack as this can be placed and boxed just above the toilet in the room, so maybe one on each loo just to be belt and braces.
With a rodding point at the highest end and one at the elbow hopefully this will keep everything moving without causing a blockage.
Would appreciate any thoughts on this.

it means 6m to the down pipe, I only had a quick look at the regs but it did say that you could exceed this if you add a vent, I think adding a vent is the key it will also stop any syphoning.
it is unlikely that both toilets would be flushed at the same time anyway
If it was my house I would probably try it and see what happens but make the elbow a swept tee and put a cap on the spare end and leave it accessible.
I have added the uk building regs file see if you can make sense of them, the theory behind them will be the same as the french ones.

the way you have desscribed the runs i would go for another run outside ,with sep stack
The last thing you want just to save a bit of time is to have (sh1t) in your house when it goes wrong which is going to happen with all those differnt drops and bends … just remember to vent above the roof and not near a window , new rules are comeing to france so get it right and save yourself time and money, go to the Sivom website for all you french waste opptions

Looks interesting Scott, how much do they cost?


Thanks for taking the time to look Andy, forgive me if I’m being obtuse, that’s 6m max to the down pipe? Which then presumably speeds the process up.

Putting the vent at the furthest point isn’t a problem but as you mentioned 6m is shorter than proposed (plus bend) and only a single toilet defeats the object slightly,

I may have to look into mincers or is it mascerators except they’re quite noisy, anyway thanks again for your input.