I am replacing a tub with a shower on a slab floor. I have cut the slab to allow repositioning the drain to the center of the 34 x 60 inch shower, but am reluctant to cut in the other direction to replace the existing 1 1/2 inch drain with the code-required 2 inch drain (the former tub drain cuts into the toilet drain in some fashion, 17 inches away). Rather than cutting the slab back to the wall with the risk of breaking underground plumbing, I would like to use the existing 1 1/2 inch tub drain for the shower. The supply to the shower will be a standard, mixing shower head with 1/2 inch supply.

Will I have any problems with drainage, or am I good to go?

Thanks,
Karl

Hi Karl,

While we like to recommend 2" on our drains, back in the days that I broke into plumbing everything was 1 1/2" galvanized and they're still working. The inspector might not like this but I say , use the 1 1/2" tub drain and good luck. Tom

Tom,

Thanks for the quick reply.

I have since rotary-hammered the concrete all the way back to the wall in order to reach the fitting and replace it (photo). Too hard! The existing sanitary tee for the tub drain is tight up against the tee for the toilet which is immediately below. I would have to replace the toilet drain as well and there's no room to work without another day (or more) of chiseling concrete out from under and around the vent. "Fegettaboutit!"

As I see it, I have two options: 1) go with a inch and a half shower drain as you suggest at risk of some subsequent inspector (not an immediate concern ;) telling me to do it over, or 2) install a 2 inch shower drain and employ a 2 x 1 1/2 reducer to connect to the existing 1 1/2 inch drain (using a high grade marine putty to "fare" the inside of the adaptor to ensure there is nothing to snag on). Option 2 would give the appearance of a two inch drain...

Which would you recommend?

Karl

Good morning Karl,
You've talked about inspectors but you've never told me if there was a permit pulled and if you'll be inspected. Inspectors are master plumbers, he's going to snap right away that you've choked the 2" shower drain down to 1 1/2"
Inspectors have a habit of getting downright persnickity if they think you're attempting a "end run" around code. Are you or are you not permitted? My answer will depend on your reply. Tom

Tom,

Not permitted.

Thanks,
Karl

Karl, go with the 1 1/2" line and good luck. Tom