Really simple question, I've got 25mm mdpe pipe coming out of 110mm pipe/duct in the build.  Is there a widget/grommet that I can use to seal the 110mm pipe round the 25mm mdpe pipe, thought about expanding foam but not sure if the chemicals are safe to use with mdpe?

 

Thanks Marek

Yeh - I use these if you want a really tidy look, but don’t forget to insulate the MDPE first and centre it in the rubber outlet using some more insulation offcuts. 
 

https://www.roofgiant.com/guttering-fixings-accessories/deks-110mm-universal-waste-adaptor/

 

Perfect, that'll do nicely.

You will still need to insulate if this is less than 300mm from the perimeter of the foundations. Rockwool plus 25mm wall pipe lagging will suffice.

Exp foam is fine with MDPE btw  Just spray a little water into the 110mm pipe before applying to help it cure / expand.

Yep all insulated, pipe insulation from edge of build to rise, about 12m worth.  Did it as I was laying the ducting and pipe, probably one of the only jobs I did in the correct order...  I didn't fancy shoving insulation round the water pipe down through the bend.  I do worry that If I/someone ever needs to replace then pulling the pipe out + insulation then replacing might be a hell of a job though...

 

Found this factsheet if it's of any use to future readers.

 

Fact sheet - laying a new supply pipe.pdf

15 minutes ago, crispy_wafer said:

I didn't fancy shoving insulation round the water pipe down through the bend.  I do worry that If I/someone ever needs to replace then pulling the pipe out + insulation then replacing might be a hell of a job though...

That pipe will last longer than us mate