Adding an outside toilet to caravan

[Tom]

So, I'm in the process of making an outside toilet for the builders to use, this I want to plumb in to the waste already connected to the caravan (the new toilet will go right next to the caravan toilet, except outside). At the moment the caravan toilet comes down in to a P-trap and then shoots off to the treatment plant. There is no soil stack and other than some occasional gurgling, it seems to work OK like this. I want to replace this P-trap with a T, to allow me to add the new outside loo. I'm worried that flushing that will cause problems - eg suck the water out of the trap in the caravan toilet. Should I be worried? If so, do I need to install an AAV?

Thanks all

[ProDave]

You don't need a P trap, the toilet has it's own trap, so trap following trap is a bad idea.

 

You just need a Y branch to take the 'van toilet in one side and the outside toilet in the other.  While you at it put in a 90 degree branch to feed a vent pipe that you can strap to the outside of the outside loo building to vent the run.

 

Depending on the eight of the existing pipe, you might need a raised platform for the outside loo.

[Tom]

Thanks Dave, how big/high should the vent pipe be?

[ProDave]

You might as well make it to just above the roof or the caravan or outside toilet.

[joe90]

1 hour ago, Tom said:

Thanks Dave, how big/high should the vent pipe be?

Just above “nose height” ?

[Tom]

9 hours ago, ProDave said:

You might as well make it to just above the roof or the caravan or outside toilet.

 

In 110mm?