Soil pipe for new downstairs toilet

[xxbernie]

Hi all!! Although I am new to the site I have used it numerous times to resolve small queries regarding many of the DIY jobs I have done. Now on my third renovation I have come across a very simple to solve problem but just want to check I am barking up the right tree.

I have a very conventional 1st floor toilet with full SPV. This goes directly down, through the garage and into the screed floor. It then hangs a 90deg bend and travels under the house until it is directed toward the first manhole.

As luck would have it, the soil pipe runs as near as dammit to where I want to put a downstairs loo. I have no problem breaking into this and routing the new soil pipe into this.

Bearing in mind I will be fitting a sink in the same downstairs loo area and will but the drainage from this into the new section of soil pipe, do I need to fit an AVV to the new toilet's outlet?

(I am assuming 'yes' as I will need to counteract the negative pressure created by the loo)

 

[Rico99]

Fit an ANTI SYPHON TRAP to your basin.

Rico

 

[Nige F]

Better still a Hep V O waste valve

 

[xxbernie]

Many thanks for your replies.

I have now unearthed the soil pipe I need to break into. Due to its position being not quite where I needed it (isn't that always the case!!) without breaking up a perfectly good patio, I am re-routing and will definitely fit the AAV now. This is due to it not directly linking into the existing pipe if that makes sense.

 

[Hugh Jaleak]

If you havent already planned for it, I would strongly recommend you fit a manhole at the point where your new drain joins the existing pipe. In the event of a blockage between here and your new loo, you have access to get rods in to clear it.

 

[xxbernie]

Know where you are coming from but as the distance from the existing manhole to the new section of pipe is so close there is little benefit. I will also stick an access point at the first turn where the soil pipe leaves the house.