replacing shower base

I am in the process of replacing an old tub with a retrofit shower base. I removed the old tub and called in a couple of plumbers for estimates on installing the new Swanstone shower base with a Oatey No Calk drain. When the plumbers came out I was informed that I needed to replace the existing 1.5" waste pipe with 2". The estimates I got ranged from 2,000 to 3,000 to replace the pipe back to the vertical stack (only about 3 feet away) WAY MORE than I was prepared to spend for this remodel.

So now I'm considering just installing the base myself. Cutting the existing copper pipe back a bit and then coupling it to a 2" pvc dwv using a 1.5 to 2" converter piece to connect to the shower drain. Or alternately going 1.5" all the way and replacing the rubber gasket in the drain with one for a 1.5" pipe (saw this on Oakey's website).

I know that code says it should be 2" for shower, however I never experienced problems with the tub draining before and I have a shower stall in another bathroom that has only a 1.5" drain pipe (was done when 1.5" was the standard I guess) and have had no problems with that. So, code aside, is there really a problem of doing it this way? Apart from not passing possible inspection if/when I sell the house (assuming they discover it) are there any problems I'm courting here?

A 2" drain has 1.78x the area of a 1.5" drain. It also has a much smaller lip to hold the water in prior to it overflowing than a tub (and a tub has an overflow to prevent that from happening). Depending on where you live, the town may make you tear it out and fix it, or, it may become a condition of sale.

Fixing this yourself is probably less than $50 in parts. Unless they have to rebuild the floor structure to run a new line, it shouldn't be too bad to cut out and replace things with pvc. My guess is that you have cast iron in there. If it is pvc, even less. Unless there are extenuating circumstances, I think that is way overpriced. Is this in a wood structure, or do they have to tear up a concrete floor?

Necking down a drain line (from 2" to 1.5") is never a good idea or one that will pass code. It also leads to clogs.

Okay. I guess I will do this right rather than half-***ed. I removed the section of floorboards running along the pipe. There is a waste line coming off of the vertical waste stack running to the toilet. There is a T-joint in this which connects to the section of pipe that runs to the tub/shower drain. See the attached pictures.

As I understand it, I can cut out the T section from this waste line and replace it with a 2" T section of PVC using couplings to connect to the existing cooper line and then run 2" PVC to the shower drain in the same space the current 1.5" drain line runs.

Does this sound right? Any tips/tricks/things I should be aware of or is this really as simple as it seems?

I'm sure we can make it difficult. My first question is where is the vent for the tub/shower? Other than that (which may not be an issue), the only advice I can give is don't throw away the old copper - recycle it and you can probably pay for a nice bottle of champagne with which to celebrate the new shower.

The vertical waste stack which is not visible in the picture but is just about 2 feet from the join to the pipe going to the tub/shower vents directly up out the roof. Is that sufficient? Do I need some additional vent? There wasn't one when the tub was in place so I'm hoping this is still cool as is.

I may be wrong (one of the experts will surely comment), but I think the shower will need its own vent -- otherwise the toilet flushing could siphon the trap dry. I'm surprised you haven't smelled sewer gas at the old tub drain in the past. Now that I take a closer look at it, I'm also surprised at the copper T at the joint -- I'd expect a Y. Even if I'm right, this is all fixable. Running another vent for the shower will involve more carpentry than plumbing.

Here's a dumb question. When I replace the waste pipe section is there any trick to ensuring that there isn't standing water in the pipe? And any way of clearing it before I start? Or do I just make sure and have plenty of buckets/towels on hand?

If it is sloped properly, and you don't have a blockage, there should be very little there - but, if it isn't done right, there could be!

Don't let anyone flush a toilet, or other things upstream, though.