I have a leaking shower drain on the second floor of my home. When we bought the house last year, the floor of the one-unit fiberglass shower gave a bit under my weight. You won't be surprised to learn that all that flexing caused the lip of the drain to separate slightly from the shower floor. The flexing floor has since been repaired by a contractor (I can provide details if you wish); however, the leak that was opened by previous floor flexing has remained a recurring issue. Every couple of months, I retry a quick fix (forcing a tiny amount of silicone caulk between the drain lip and the shower floor). No luck, and I'm getting tired of painting that downstairs ceiling.

Deciding to take care of the problem once and for all, I have cut a hole in the ceiling to gain access to the drain. Unfortunately, I can't get to the bottom of the drain because all I can see is the drain pipe going up towards the shower through a small hole in a piece of plywood. At least my having cut a hole hole in the ceiling has allowed me to verify that the drain is the source of the leak.

Since I couldn't even see the drain from below, I next approached the leak from the top of the drain... treating it like it was a tub drain since it looks like my drain is glued to the PCV pipe rather than held on from the bottom by some kind of bolt. I removed the strainer and then successful unscrewed the plastic lip of the drain from the rest of the drain body. The lip part of the drain has lots of old plumbers putty in its threads, but otherwise nothing appears to have been damaged in the process of separating the two parts of the drain.

My main question (at last) is this: Can I just clean up the drain lip and the shower floor beneath it, apply a thick bead of silicone to the area, and screw the lip portion of the drain back in? The help person at Lowe's said this strategy would work well if the source of my leak was a gap between the shower floor and the drain lip, but I wanted verification by a professional.

If I'm on the right track, I also need to know the following:
1) Since I've garnered from previous posts that silicone caulk is better than plumbers putty for the drain lip of fiberglass shower floor seal, how much caulk should I use (how big of a bead?)?
2) Should I apply the bead to the lip of the drain or to floor of the shower?
3) How long should I let the caulk cure before I test the seal?

Thanks so much for your help!! I've scoured your on-line archives before tapping your time, but I can't find any posting in which someone has tried to reseal the drain lip to a shower floor while threading the lip back into the drain (as opposed to tightening a bolt from the bottom).

You couldn't find reference to shower leaks on this site? Look on page two in the thread, "Standing Shower Leak".
I need to know what material the shower drain's made of. Metal or plastic? I'm putting up a image of a typical shower drain,(see image). As you can see the drain's secured/glued to the trap raiser. It will be imposable to work from the top. You will have to cut the plywood subfloor to get to the nut so you can loosen it, raise the lip and reseal it. You have another problem. The showere floor should have been bedded when it was installed. This consists of puddling mounds of mortar or cement aruond the drain and "spongy spots" in the shower floor. Without the added support your problem will surface again in the future. Before you apply a small rope of silicon jel under the lip make sure you dry it off and wipe off the excess that's squeezed out. Allow the caulk to cure and set up overnight.
Good luck, Tom

Tom, Thanks for your quick response (as always)!

I miswrote... Before posting, I found lots and lots of your insightful posts on how to deal leaking plastic drains. What I couldn't find was a message addressing how someone goes about resealing the drain lip to the shower floor if the drain was glued in rather than attached/tightened with a nut from the bottom. My best guess is that I have a solvent weld drain... but I'm attaching a picture for your call on this.

As you can see in the picture, I've already backed the top part of the drain out... I hope that this wasn't a mistake since this is the strategy that the helpful (truly) person at Lowe's suggested.

If I can't approach the drain from the top, I suspect that I'll have to resort to using a Wingnut. Cutting through the plywood (picture from the bottom attatched) could be difficult because of the manner in which the contractor fixed the flexing in our shower. He drilled numerous holes in the fiberglass and shot in some type of material (presumably foam, but I wasn't smart enough about drains last year to ask the right questions about details). He then glued a custom rubber-like mat to the floor to cover the holes. Although I haven't heard of anyone else dealing with this problem in this way, the flexing has been gone for over a year. I would think that I am going to see nothing but a bunch of hardened foam if I cut through the plywood.

Thanks again for your time!

This is indeed a solvent weld drain and not a regular shower drain as I have pictured.
It would seem that a new gasket would solve the problem. Or am I missing something? Regards, Tom

Thanks Tom. I'll use PVC cleaner and a bit of sandpaper to prepare the drain lip and the area of the shower floor immediately surrounding the drain. I'm hoping that a ring of silicone and a day's wait will have me dry for years to come. BTW, I teach college courses on human behavior. Everyone says that you can't trust anyone anymore... and then there's people like you. When I looked at all of the posts you have done over time that have helped homeowners with limited means, I was amazed by your generosity with your time. Thank you so much for helping people like me!

Thanks for those kind words. I'm retired and just wish to pass along some of what I've learned over the years. Answering plumbing questions keeps me sharp and makes me feel like I'm just not some old fart waiting to die. It makes me feel like I still have something left to contribute. Thanks again. Tom