Strap on boss for cast?

[tolly]

Hi, Ive got to boss into a 4" cast stack in the next couple of days, I've never done this before, normally have cut a section of cast out and fitted a boss pipe with ferncos or completely renew the stack in PVC.

I cant do either of them in this situation and I need to use a strap on boss, am I right in thinking timesaver do a strap on boss made for the job, im guessing it seals with a rubber washer? I don't like the idea of trying to silicone a normal strap on boss on.

Any tips with regards to drilling the hole for the stack, I was just going to take it slow with a bimetal holesaw?

Im guessing somewhere like BSS might hopefully stock these timesaver fittings

 

[Deleted member 7121]

The timesaver ones come with rubber washer got one from drainage centre the other week or Graham's also do them , nice and slow on the drill