I am at present fitting a saniflo system on one of my jobs and found that there wasn't much info out there so I am going to show how its done using a strap on boss.
First thing i found out was that using a plastic one on cast is seen as a bit of a cowboy job as they nearly always end up leaking due to differences in expansion from cast to plastic.
I found out that a company who make a product called "Timesaver" make a cast iron strap on boss so i ordered one from my local plumbers merchant at a cost of £36.00
This looked like a quality bit of kit....
Now its time for the hard part....drilling the hole.
I bought a 64mm starret hole saw and put it on my cordless dewalt drill.
I soon realized that this was going to tke som time and lots of power so i changed to a plug in drill
The progress with the hole was extremely slow with the hole saw as it seemed to blunt very soon after starting.
I never used any lubricant/cutting oil as i read somewhere that the cast does not need it and it may slow the process even more.
After about half an hour it looked like this...
After about an hour ..including a few breaks in the drilling i finally managed to get through it..
Every so often i ran the blade under a cold water tap to cool off.
I would like to think there is a better hole saw for this as this was quite tedious.
Most important thing with this is not to try to rush.
If you break the cast then it would be necessary t remove the whole top section and replace with plastic Hidden Content .
The other way would be to stitch drill it but i wouldn't be too happy about tapping out the middle bit.
Once i got my hole i decided it would b a good idea to clean off all the paint from the edges with a grinder...
Next i decided to put some SLX silicone on the rubber ring and all connecting parts..
Not sure if this is necessary but just to make sure.
After that i fitted the rubber and clamped it in place with the boss strap.
I was a bit weary of over tightening this for fear of snapping the cast strap.
You can always tighten a little more if it leaks on test.
So now it looks like this...
fitting this would be easier with 2 pairs of hands but is possible on your own...had silicone all over my hands Hidden Content .
Next i put the rubber 'o' ring around the a pipe reducer.
Or you could put it directly on to a 40mm waste pipe, but i was using 32mm.
Then push it in the hole and put the front cover on....this creates a compression joint.
Now looks like this
Once this is done you simply solvent weld your new pipe into it so it looks like this...
Here i used cuts of 15mm copper pipes to make stilts for the brackets so as not to put strain on the joints.
I used a few because this pipe will be taking a bit of weight from the nasty stuff thats going to get pumped through it from the sanioflo.
All in all the job went quite well and finished up looking like this
All i need to do now is find a suitable insulation for the 32mm pipe that is ok to use externally and looks ok....sure there is something on the market.
Hopefully this will help someone who is thinking about doing this themselves or just to see roughly how it should be done.
Another way is to cut a section out with a grinder (not easy either when on a ladder) and joining plastic with a rubber joiner above and below with jubilee clips.
If you do go down that root you must be sure that the upper sections are well secure.