Pumped Grey Waste from External Building

[markptrueman]

Hi

We are putting a cabin in the back of our garden and are looking to take grey waste water from a sink and shower back to the main drain of the house.

I was looking at one of these

https://www.plumbworld.co.uk/flo-force-elite-lifting-station-250w-with-2-inlets-101425-1252983

However, I'm not sure on how to do the pipe run for this. We are doing a 750mm trench which will run about 10m (with a couple of slight bends) in 20mm MDPE for mains cold water and I was intending to run the waste pipe from the above in the same trench.

Am I good to just use 32mm MDPE flexible pipe for this? I assume I need to follow the 1:100 fall off as specified, even though this makes the laying of this pipe slightly more difficult. Id rather just lay it flat along with the mains pipe if I can.

Any other suggestions on getting waste back to the house would be also a great help

Thanks

 

[just pumps]

Can you get a 1:100 fall or more from the cabin back to the house main drain considering it must not rise anywhere and you need to investigate how you will join the MDPE to the pump outlet.

 

[markptrueman]

I think the fall should be doable, but as you say, MDPE is 32mm OD whereas the fitting would need to be ID of 32. The output can also be 22mm without an adapter in place. Not sure how to manage that join.