Flex-seal adaptors and similar

[Steady]

http://www.flexseal.co.uk/newsite/_uk/products/adaptor.asp

Can anyone see a problem with using one of these flexible rubber couplers 'upside down'to connect 4 inch plastic soil to a vertical run of 3.5 inch cast iron,i.e. cast iron below,plastic above?
Don't want to replace the whole soil stack as it is surrounded by an expensive impressed concrete driveway.

 

[Nige F]

Well..i`ve calculated that a Richard,acellerating @ 32 feet per second per second until reaching terminal velocity....should ,within the normal coeficient of the stool tables.marginally deform,or in 79% of occasions,when accompanied by 6 or more litres of lavatorial water...disintegrate .Therefore most of the waste should pass the constriction without difficulty...an air test to check soundness is a different matter......Yes, I`ve used them to good effect,and considering the horrible job of making good printed concrete...go for it. (air tests only apply to new work, not replacement.)

 

[ChrisR]

That'll be a "no" then?

 

[fitz1]

there is a fitting designed to fit into cast or clay and converts to plastic soil.i got it from my local supplier(not national)u will need to hunt. maybe plumbcenters drainage center.

 

[Steady]

Thanks for the replies.I have found some useful stuff on the OSMA website
and am pretty sure that there is a suitable adaptor available.I guess by the fact that you have to hunt for the right part means that in general you can 'get away' with using something else like the Flexseal.
The same way that you can use a Multikwik pan-connector to join plastic soil to salt glazed pot-not the right part but more readily obtainable.