Hi, it's about bathtub - shower conversion.

[Galina]

I have a fiberglass bathtub + walls (4 pc) unit now. Want to replace it with same thing, but with shower, not tub. Tub has a 1 1/2" drain and 2" required for most showers (MA codes). 1 1/2" can still be used with low volume shower heads.
I found out that I can get a " Reducer Pipe Fitting" to connect 2" shower drain to a 1 1/2" drain pipe. Any hidden problems here? Good idea or not? Don't want to open the floor and redo the drain pipe.
Will appreciate any feed back.

 

[Breplum]

1.5" drain, Bad idea. 2" is the way to go.

 

[Sponsor]

 

[Galina]

Why it's bad. It's a top floor shower, water flow is on the low side always there, and I have this low flow/volume shower head anyway.

 

[cmbusker1455]

We recently tore out our old fiberglass tub/shower and replaced with just a walk in shower. I had the exact same issue, I had 1.5” copper pipe for the drain pipe, which emptied into the cast iron 4” toilet drain. Problem was, that cast iron right below the toilet is old, terribly rusted, and I didn’t want f to accidentally break it by trying to get the 1.5” copper fitting out of there. So I just left the 1.5” copper on the toilet side, and connected the new 2” PVC to it using a 3001-215 Fernco. I had to order it on Amazon, no local stores had it in stock.

If it’s just about reducing 2” to 1.5” PVC that should be fine, but do it far enough down the drain pipe where that reduction won’t cause a problem.

Here’s a pic showing where I did our reduction, all the way to the right you can see the fernco and the start of the 1.5” copper pipe. From there its only a few inches of copper pipe, then there’s a couple bends and it empties into the cast iron sewer pipe. The next two pics show the original drain piping, and in the last pic you can see the bends and connection to the drain pipe that aren’t visible in the first pic.

When we remodel the rest of the bathroom, we are planning to replace as much of that cast iron pipe with PVC as we can. My plan now is to make it PVC from the toilet flange all the way to where the shower drain connects. At that time, I’ll extend the new 2” PVC shower drain all the way. But for now the Fernco is working great and I haven’t had 1 single drip from it. Granted, I did use an impact drill/driver to tighten the bands, specs say to tighten to 60ft lbs of torque.

 

[CENTRALFL]

Just a DIYer, but everything I read about reducing was a) don't, or b) if you have to do it, do it where you can reach, as that reduction will be catching stuff. You'd want to be able to reach it when it's time to clean a clog.

Either way, it sounded like you were going to redo it in the future so likely not an issue for you, just more an FYI.

They allow reducing here, as long as you stay below some GPM amount. Something about the conversion from tub to shower was very common, and the volume of piping technically allowed it.

 

[cmbusker1455]

Just a DIYer, but everything I read about reducing was a) don't, or b) if you have to do it, do it where you can reach, as that reduction will be catching stuff. You'd want to be able to reach it when it's time to clean a clog.

Either way, it sounded like you were going to redo it in the future so likely not an issue for you, just more an FYI.

They allow reducing here, as long as you stay below some GPM amount. Something about the conversion from tub to shower was very common, and the volume of piping technically allowed it.

Yeah I agree with your research as well. In reality, reductions are sometimes unavoidable, so you just work with them and try to create the best situation you can. One thing about my situation was even if I had been able to get the old 1.5” fitting out of the cast iron, there still would be a “reduction” of the 2” pvc so that it would go into the threads of the cast iron drain port, which is only 1.5” size anyways. So I figured, don’t risk cracking the cast iron toilet drain and play it safe for now. We’re planning to do the rest of the bathroom remodel this coming October 2025, and that’s when I’ll redo the toilet drain.