Charlie, What is the construction of this shower? Is it tiled, floor and ceiling? Is it a prefab fiberglass or acrylic unit? It is a shower in a tub? If so, what type of tub...cast iron, or fiberglass/acrylic? Since you have access to the shower body, does the shower body remain dry when the shower is running? Leaks typically come from the parts that move...in this case the valve assembly or if an acrylic/fg base, the drain. Since it's only 4 years old, I presume the unit has ceramic disc valves...they sometimes can leak and can be repaired by snugging the stem up just a bit. Depends on the type. Stem leaks can leak all the time, or just when the unit is not in use. If the shower head was recently replace, it's possible the threads were crossed, or no teflon tape or dope was used, and it's a slow leak through the threading. That type of leak would only occur when the unit is in use. A drain leak in an acrylic base may only leak when the user is standing in the shower and the base is flexing. There are a couple other options if it's tiled. Mongo

You should be able to shower with the pan liner in, cement board up(actual cement board), and shower curtain. Build curb, floor mud preslope, install liner(no fasteners), and another 1“ minimum floor mud on top, float curb. Cement board walls, silicon the edges, tape the seams, thinset level, and red guard the curb and walls. There won’t be any leaks at this stage. The tile provides merely aesthetics in the grand scheme of it all. They help shed water but offer very little to the game of waterproofing. It’s an illusion! Red guard is completely unnecessary and I don’t recommend it on every surface. Don’t use it on the bottom 6” or liner height of wall, or the top 3ft of wall, or on the pan floor, and never on drywall. The cement board will be submerged in the pan tile deep so it needs some breathing room. You’re just asking for moisture to accumulate in the wall but wait there’s a moisture barrier behind the cement board. That barrier got screwed up from the durarock install but you siliconed each stud, right? That’s called a hole in the plan. Welcome to the shower install conflict. For the love of grout don’t seal it! A 1/16th square. That’s impressive. The line of a dull carpenters pencil. You’d be lucky to buy board that’s within a 1/16”. I’ve worked with all kinds of framing types and they’d throw you off the deck if you were fussing over a 1/16”. Finish guys now that’s a different story. A 1/2“ square per 12ft, 1/4“ plumb average per 8ft, and a 1/16” level per 4ft in all reality is the best workmanship you‘re going to find in any home. Any thing else is an empty promise or a rubber square.

When I installed a Dreamline pre-fab shower base, the directions were to leave an opening in the concrete that had about 3-4" open around the drain pipe. I got the pipe aligned as well as I could, and then set the base in place and pivoted/moved the trap and pipe slightly so it would line up with the hole in the shower base. We then cemented the pipe joints so they would stay in place and the pipe would stick up through the hole in the base. When we set the shower base it had thinset under it to keep it level and supported, but directions said we did not need to fill in the area around the p-trap with cement. That part of the base was reinforced and it was just left with a base of sand. The drain fitting in the shower base was installed before it was set in place, and as we set the base in place a rubber collar slipped over the 2" pipe that stuck up from the P-trap. There was a threaded inside fitting on the flange in the base, and as you screwed the fitting down with a special tool (supplied) it expanded the rubber collar so that it fit tightly over the PVC pipe. Then we trimmed the top of the PVC pipe and popped the decorative grill into the drain. My point in explaining all this is that if you use a similar design shower base, and you have a 2" drain line, you would only need to jackhammer a small section of concrete out to install a 2" P-trap, and would only have a very small section of concrete to replace. However, if the shower drain pipe is 1.5", you have a lot more work to do if you want to meet code. Bruce

Update: the roofer came back and checked all of the gutters and confirmed that there is no drain pipe outlet into the gutters, but we couldn't figure out where the drain pipe ended up. However, he did find an old downspout tucked away in a weird spot in the soffit, and removed a large clog from that, so I started the AC again just to see if the water would start draining there. It did not, but water did start dripping from another area of the soffit (halfway around the house from the unit!). Anyway, it was obvious that we weren't going to get any answers without an expert. So I called in an AC guy, who quickly figured out that the drain pipe runs down into the basement (why go all the way from the attic to the basement instead of out into the gutter?), and that it was badly clogged. He blasted out the clog and added a union so we can easily shop vac it ourselves now and again, and all was well. He also installed the overflow emergency switch that the previous owners left sitting (unconnected) in the drip pan. Grrr... The relationship between the soffit/gutter work and the leak is still a mystery. It could be coincidental, but my guess is that the drainage pipe has been clogged for quite some time, and the only reason we didn't have a major indoor leak before now is because the water was seeping into the soffit and slowly draining through all of the holes that the roofer patched (in addition to some large holes in corners/dormers, he also patched about a million small carpenter bee holes). Regardless, all the water is now going where it belongs, thank goodness! I've got a dehumidifier running in the rooms that got wet, and I'm hoping we can get away with just repainting the ceiling rather than replacing all of the drywall. I do worry about what might be growing inside those soffits, though - the gutter guy said a ton of water and debris came out of the old downspout, so I can only imagine there's more where that came from. Thanks for your guidance as always!