black rest bend or 2 x 45 degree bends as rest bend?

Good evening, need to replace my old cast iron soil stack including the bend at the bottom and a short length of clay pipe. I ideally need a black rest bend as the top of the horizontal pipe under the driveway is only 150mm below the finished surface of the drive (probs why the pipe is broken, new one will be encased in concorete), so I don't want the top of an ugly browny/orangy coloured rest bend visible. Anyone know if there is such a thing? Failing that I seem to remember reading somewhere that it is possible to use 2 45 degree bends as a rest bend, if so, is there a minimum length pipe I need between them, or can I just push a single socket bend into another one?

A related question, as the stack is on the front of the house, I am considering stopping it just above the WC level and putting AAV on the top as I believe this will look better than a stack all the way to gutter level, any reasons why I should not?
Thanks, Lee.

 

Min 200mm radius, use two double socket bends and a cutting of pipe between them.

 

I’d just use a black 90, most of the clay ones are just as tight, if not tighter, than a normal 90.

I think the stack would look odd if it didn’t go upto roof level.

 

Always best letting a stack breathe in and out IMO not just in.

 

Blocking off an open vented stack can cause all sorts of issues, drains need to breathe. Any back pressure created wil lcurrently vent out the top, block it off and that pressure will have to find another way out.... Some people have found out the hard way in the past, problem downstream have required the sewer to be jetted, the pressure bow wave caused by the jetter has redecorated their bathroom....