I am having a bathroom renovated. After replacing the old tub, the plumber connected the drain pipe of the new tub to the old system with cast iron pipes, connecting them to the old system with screw tightening sleeves, rather than threading pipe fittings. I am concerned that this type of connection might leak after a while. Is that a common practice? I live is a concrete building (COOP) on the 12 floor, and a leak could be a BIG problem.
Should he have simply replaced the old pipes with new ones with threaded fittings?
Thanks

Those "sleeves" are called No-Hub Bands and I've installed entire high raise condominium drainage systems using them. That was 25 years ago and no complaints yet. Don't worry. The connection's both safe and secure. Regards, Tom

Speedball is right, that is a really popular and acceptable method of coupling pipe. You can find this on almost all the cast iron stacks/underground pipe installed today and if you look closely under your car you might see hose clamps(gear clamps) used there too. And if for some reason it does leak it's just a matter of tightening the band with a flat-head screw driver or a 5/16" (on most brands) ratchet or nut driver. Just make sure not to over tighten though as you could tear the clamp.

Thanks a lot, gentlemen. This makes me feel much better. However, the guy putting down the floor in the bathroom is going to pour cement on these connectors, so a leak could be very difficult to correct, which is why I worried.

As long as its on there tight it will be good... but
If you're losing sleep over this and must be absolutely sure, run water down the drain for at least a continuous 5 minutes and check for leaks, and make sure the band is tight before he pours the concrete.