lead bend and brass flange

I had new plumbing roughed into my basement for a bathroom when we were pouring a new slab. The plumber used a lead bend for the toilet. Now, I have just the lead bend stub sticking out of the new floor.

I want to complete the plumbing myself and have installed plenty of toilets and flanges, but never on a lead bend. I've also done plenty of soldering of copper supply pipes.

I have been reading and I know I need to use a brass flange, but I have read both that these need to be soldered on and also that they can be hammered over the edge.

My question is whether it is necessary to solder the pipe to the flange or does the hammering method work?

Also, it needs to be cut down considerably (it is about 12 inches high at the moment) so how much pipe should I leave sticking up to accept the flange (before attaching). And finally, what sort of equipment is necessary to attach it, by whichever method..

Thanks for any help.

I'm very surprised anyone is using lead bends on new construction these days!

Keep in mind that the toilet flange should be installed on top of the finished floor. Flaring the lead out over the flange ring is all that is required. You'd have a hard time melting or soldering it anyways without a major blowtorch.

I'll leave the details to one of the pros...

Thanks and related question about backwater valves

So, is that the concensus then? Banging it over the edge. Sounds good to me.

I guess I just use a hacksaw and cut it down to a reasonable height?

This new plumbing has invited trouble into my basement. I was cognizant of this at the time and specifically requested that a valve be installed between the new plumbing and the main sewer line to prevent this.

The plumber put something like the one here in:
http://www.bwsc.org/Community/Safety/backwater.htm

But it didn't work! I had a sewage flood with the recent big storm (I'm in NYC). Then, again with a much smaller rainstorm last night.

On top of this, the valve is now buried under the concrete (plumber said that was okay--I'm sure that was a huge mistake). And we have radiant in the floor, so I don't want to bust it open to look.

So, what to do? Are these valves just junk? I'm thinking of putting a bigger, better one in at the exit to the house. Can anyone recommend one that really works?