Fiberglass shower drain leak

[DIY2010]

I have a leak in my fiberglass shower drain on the second floor. There is a unique situation I'd like to describe and try to get some answers. My drain leak started when my shower head started to leak. That's another long story but I think I finally have that fixed now. It dripped about a gallon a week so it was fairly significant. What's interesting though is that the drain didn't leak into my ceiling below when taking a shower. Again, it only leaked below when the slow drip began.

My theory is that when standing in the fiberglass shower, it compresses some part of the drain sealing whatever space there is. Does this sound reasonable?

One more thing. When I shine a flashlight into the drain, I see what I think is a gap in the PVC piping between the drain and the trap. What on earth could this be? I tried using a coat hanger to see if the gap is completely open and it doesn't appear it is. It feels like there is a gap but it's sealed.

Finally, I'm sure you need to know that the house was built in 1996 in case some type of plumbing standard was different back then. However I'm not sure there were any standards applied in this house. An acquaintance didn't understand why I was repairing the shower head leak by turning off my water main. I explained that there were no shut offs anywhere except at the main. I was told that this is incorrect and shouldn't be possible. Who knows. I'm not a plumbing expert.

Thanks for any help you can provide!

[HayZee518]

whomever installed the drain pan, the membrane is sandwiched between the base and drain flange and bolted up with stainless steel bolts. if this connection isn't up tight you will get a leak because the drain pan is always "wet" - I guess what you have to do is take up all the floor tile and start over.

[pushkins]

What tile floor, Op said it was fiberglass ?

Do you have any access to below the shower ?
If you look down inside the drain do you see two little slots, opposite each other or a black rubber gasket or does it look like the fitting is glued ?

[DIY2010]

Yes it's a fiberglass shower, no tile floor. I don't have access to it from below without cutting through the ceiling on the first floor.

I can't see a black rubber gasket and I don't know how to tell if it's glued.

This is a Sioux Chief drain and it looks like an 827 model (no caulk). Although the house was built in 1996 so I'm sure the model was different then.

I have fixed the slow leak coming from the shower head and I haven't had any new water damage from that. I've also taken two showers and I still can't find any new damage so this lends proof to my theory that standing in the shower compresses it and prevents it from leaking.

I'm going to try one more thing before removing the drain and possibly cutting a hole in my ceiling. A friend suggested simply trying to tighten the drain. I'll let you know if this works.

[pushkins]

If the drain "can" be tightened then it has one of two options:
1. a big nut on the underside of the drain accessible only from beneath the fiberglass unit.
2. two little slots on the inside of the drain, to tighten this you need a little metal piece that sits in the two slots and you turn it with a big flat head screw driver.

Other than these above options you have a glued drain or one other drain type with three screws underneath to unit (similar to your garbage disposal unit) but it's seldom used on this type of application.