How to Fix a Shower Leak Behind the Wall

By |Last updated on |Bathroom, Featured, Shower|45 Comments

This project explains how to fix a shower leak behind the wall by cutting an access panel in the drywall to find and fix the plumbing leak.

I noticed a water dripping from the ceiling of the walk-in closet on the main floor. Based on the floor and room layout, I realized the upstairs shower and bathtub is located directly overhead.

Leaky Shower Repair: Water Stain on the Drywall Ceiling

Leaky Shower Repair: Water Stain on the Drywall Ceiling

How to Fix a Shower Leak Behind the Wall

My suspicion is the leak was coming from either the shower water supply or drain plumbing. The problem is that I had no access to the shower plumbing because it was concealed behind the drywall – many times there will be a plumbing access panel, but there was none here. I would have to cut a hole in the drywall in order to inspect the shower plumbing and find the leak.

Showers and bathtubs can be creative in the way they leak. It’s a matter of remembering that water runs downhill and tracing the leak to the source.

Aside: Also see How to Fix a Leaky Shower Drain for a related repair.

Cut an Inspection Opening in the Drywall

I began by locating the center of the wet wall (i.e. wall with the plumbing). I gently probed (don’t want to puncture a water pipe!) for wall studs by driving a small finishing nail through the drywall to see if it contacted a stud, moving the nail about one inch left and right until I had cleared a 6 inch length. There shouldn’t be framing studs in the center area of the wet wall to allow room for the shower valve and I found my assumption was correct.

Shower Leak Repair: Locate the 2x4 Studs in the Wet Wall (Drywall)

Shower Leak Repair: Locate the 2×4 Studs in the Wet Wall (Drywall)

Here’s a closeup of the nail and test holes.

Shower Leak Behind the Wall: Check for Wall Studs

Shower Leak Behind the Wall: Check for Wall Studs

Now that I had confirmed there are no wall studs in the center section of the wet wall, I used a Rotozip spiral saw to cut a small inspection hole in the drywall to access the shower plumbing.

I cut a small inspection hole in the drywall because:

  1. I would have to repair the drywall later and small holes are easier to fix than large ones.
  2. Wallpaper is hard to repair as seams will show.
  3. I needed to locate the plumbing and wall studs before going any further.
Shower Leak Behind the Wall: Saw an Inspection Hole in the Drywall

Shower Leak Behind the Wall: Saw an Inspection Hole in the Drywall

The small inspection hole (above) allowed me to reach inside and locate the wall studs and plumbing; I also confirmed there was no electrical wiring in the wall. The inspection opening was enlarged to the span the width between the wall studs to dimensions of ~10.5 inches wide and ~8.5 inches tall.

Shower Leak Behind the Wall: Drywall Inspection Hole

Shower Leak Behind the Wall: Drywall Inspection Hole

Below is a closeup of the hot & cold copper water supply pipes and the PVC overflow drain for the bathtub. An immediate concern are the greenish/white streaks on the copper pipes from dripping water. The pipes were dry and at this point I wasn’t sure if this were a historical artifact or recently made.

A strip of blue masking tape was applied to the bottom edge of the opening to reduce the amount of drywall dust rubbed off on my arms.

Shower Leak in the Wall: Drywall Access Hole and Plumbing

Shower Leak in the Wall: Drywall Access Hole and Plumbing

Water stains can be seen on the drywall ceiling below the bathtub:

Shower Leak Repair: Water Stains on the Drywall Ceiling below the Bathtub

Shower Leak Repair: Water Stains on the Drywall Ceiling below the Bathtub

Shower and Bathtub Drain Leak Checking

A flashlight and mirror are used to inspect the bathtub drain for leaks. The bathtub was filled with several inches of water and allowed to stand for 15 minutes. No leaks were found at the bathtub drain.

Inspecting the Bathtub Drain for Leaks

Inspecting the Bathtub Drain for Leaks

Check the Shower Plumbing for Leaks

I turned on the shower and used the mirror and flashlight to inspect the copper piping, shower valve and shower head arm inside the wall. Bingo! Lot’s of dripping water.

Repair a Shower Leak Behind the Wall: Plumbing Inspection

Repair a Shower Leak Behind the Wall: Plumbing Inspection

Looking up inside the wall at the shower leak. Drops of water are falling from the shower valve:

Water Dripping from the Shower Valve

Water Dripping from the Shower Valve

“Uh Oh!” If the shower valve is bad then I’ll have to cut another drywall access panel opening to fix the valve. That would be an ugly drywall repair. Notice the water stains on the drywall and chalky deposits on the copper pipes. The drywall integrity was fine – dry and solid – in spite of the water stains. I gave it a good shot of Lysol to discourage mold growth.

Upon closer inspection with the flashlight and mirror I was able catch a glimpse of the water dripping from the shower arm (up high by the shower head) onto the shower valve. Good! At the least the shower valve is not leaking.

Water is dripping on the subfloor from the shower arm and elbow next photo. The white stuff on the 2×4 base plate is drywall dust when I cut the access hole:

Repair a Shower Leak behind the Wall: Water Dripping onto the Subfloor

Repair a Shower Leak behind the Wall: Water Dripping onto the Subfloor

The shower leak is inside the wall at the connection between shower arm and elbow behind the tile:

Shower Leak behind the Wall: Shower Head

Shower Leak behind the Wall: Shower Head

The shower head and escutcheon (trim plate) are removed to get a look at the shower plumbing inside the wall:

Shower Leak inside the Wall: Shower Arm and Wall Tile

Shower Leak inside the Wall: Shower Arm and Wall Tile

This project is continued in How to Fix a Shower Leak Behind the Wall – Part 2.

Take care,

Bob Jackson

Copyright © 2019   Reproduction strictly prohibited.


  1. Penny October 25, 2009 at 9:57 pm - Reply

    Thank you for such a riveting article!
    I just bought a house, that has a leak behind the shower wall, and I wanted to see if anyone else had fixed a similar problem. Happily I found your terrific article. And I realize it’s a lot bigger task than I could ever hope to accomplish on my own. I especially like how you made the detection hole large enough to locate the source of the leak but small enough to cover with a pretty Grill, in case you needed to go into the wall again. That was clever! And great to follow along with your photos…
    Thanks again for the great insight.
    Penny in Las Vegas.

  2. grindit April 16, 2010 at 5:21 pm - Reply

    Thank you, our problem was exactly the same.The shower/tub above a walk-in closet/pantry,where the twotop shelves were for towels and wash cloths.They were wet andI had to shut the bathroom shower down.I ended updoing everything that you did {taught me}.It ended up being the valve,
    26 years old! Thank you again,Iused the same vent cover because your
    pictures made it look better than the access panels on the market.
    You dont have to cover it up with a piece of furniture. THANKS!!!

  3. frankie December 11, 2014 at 4:12 pm - Reply

    where my shower arm connects to the plastic piece behind the wallpaper? I was wondering what’s the best way to make the area I cut out look good cuz I’m going to replace that little section of wallpaper I cut out to fix my cracked plastic piece with drywall?

  4. Beth February 10, 2015 at 2:08 pm - Reply

    Your article and pictures were excellent. Thank you for posting!

  5. GT February 25, 2015 at 2:21 pm - Reply

    Great Article and pics! Can you come to my house? haha.

    Question: if you had found the shower arm leak by just removing trim plate and shower head, would cutting that big access hole on the other side of the wall have been necessary? I understand it would be good for checking for other leak sources as well but if there was only the one leak at shower arm and elbow?

    • Bob Jackson February 25, 2015 at 6:46 pm - Reply

      In retrospect cutting an inspection hole in the drywall wasn’t necessary to fix this particular shower arm leak. The shower arm is just one of a half dozen water supply and drain plumbing connections where leaks can occur, so I’m satisfied with the plumbing access panel for future needs.

  6. Kaye March 11, 2015 at 6:17 pm - Reply

    We have fixed the leaking shower but there is a bad musky smell left behind, how could I get rid of the smell (hoping u have had to deal with this problem). THANKU for your help.

    • Bob Jackson March 12, 2015 at 7:09 am - Reply

      The odor will persist until the area inside the wall, floor or ceiling is dry. The musty odor suggests a long term leak and mold.

      Did you cut an access panel in the wall? Have you determined what got wet including the drywall, subfloor, under the bathroom floor tile, or perhaps under the carpet in the adjacent room? Do you see mold? Moldy carpet and drywall should be replaced.

  7. Ashley Simmons March 18, 2015 at 10:09 am - Reply

    I am currently renting and have had this problem twice now. My shower in master bedroom is on a platform. After showering, the floor just below the two steps of the platform is partially filled with water, as well as my closet floor which is just behind wall of shower. The water also comes through my second bedroom’s outer wall and into the closet. Any ideas? My landlord sent a “handyman” out the first time but this time I’m requesting an actual plumber. The wall just behind the shower already has a cut-out in it that has been closed again, this is making me think that this isn’t a new thing.

    • Bob Jackson March 18, 2015 at 7:05 pm - Reply

      You have a serious shower leak that needs to repaired right away! If the home has another bath with a shower or tub, use that until the leaky shower if repaired. The landlord should be more concerned because such a shower leak will ruin the floor, carpet, ceiling drywall and cause mold. Replacing flooring, drywall and mold remediation will be way more expensive than repairing the leak.

      >> Any ideas?
      I’m guessing the shower drain is leaking given the amount of water but it could be a water supply fitting. The plumber will re-open the old cut-out in the wall and trace the leak. Also check your rental agreement for your landlord’s maintenance obligations if he/she refuses to fix the shower.

  8. Jim Schu March 28, 2015 at 6:41 pm - Reply

    Have a water leak behind shower tub wall unit, eliminated the drain, cut holes in drywall beside unit, replaced diverter and shower head, will not leak with cold water, only hot. I can hear the water dripping, cut hoes in walls where the dripping noise is, only vents and abs drains, no leaks. Next step remove tub wall unit ? No other access, why only when using hot water ? Did they bury shut off in the wall ? packing nut ?

    • Bob Jackson March 29, 2015 at 12:39 pm - Reply

      > No other access, why only when using hot water?
      So the layout of your home prevents access to the other side of the wall to cut an access panel to view the valve and plumbing connections?

      > packing nut?
      The packing nut would be an inexpensive and easy repair. Wouldn’t hurt to do that first.

      > Next step remove tub wall unit?
      If replacing the packing doesn’t fix it, try a snake inspection camera to locate the exact cause of the leak. Then you’ll know whether to open up the wall or pull out the entire tub.

  9. Nizar kashlan July 11, 2015 at 8:09 am - Reply

    i have a water leake from bathtub upstairs. The technician said he have to take the tiles and the bathtub out before he reaches the leakage. He made several opening at the living room ceiling , but said he can not resolve the problem from these. Opening. This will result in demolishing the bathroom and will cost a lot. What do you think???

    • Bob Jackson July 11, 2015 at 1:55 pm - Reply

      Has the plumber explained why the floor tiles and bathtub have to be taken out to locate and/or fix the leak? Has he determined if it’s a water supply or drain leak because that will focus the effort. Opening up the ceiling should be sufficient in most situations to find the leak, especially with a snake inspection camera. Before committing to expensive demolition work I’d call another plumber for a 2nd opinion.

  10. Angel May 16, 2016 at 12:15 pm - Reply

    We have a stall plastic shower in the master bedroom. Before walking into the house is the foyer where the master bedroom is above. When looking up there are several wet spots, squishy spots where the paint is. Also, behind the toilet is the same squishy spot. Also the laminate (fake tile) is peeling where the water gets it wet from shower. The leak happens when showers are taken. Also our bathroom gets mold on wall quickly I clean it with bleach and we leave the door open when taking shower as to avoid this. We aren’t sure where the leak is coming from and if there will be water damage/mold in bathroom. we are getting a contractor (friend) to take a look. How would you fix a leak in a stall bathroom like that? and much would you think it would cost?

    • Bob Jackson May 16, 2016 at 9:05 pm - Reply

      You need to find what’s causing the leak. Shower drain or water supply plumbing? To do that you must cut an inspection hole in the wet wall or ceiling below the shower pan. You may want to begin with a minimally invasive approach by drilling a small inspection hole for a snake inspection camera to look at the plumbing inside the wall and ceiling.

      Google “home repair cost estimator” to get an idea job prices. A lot depends on the nature and location of the leak, whether a wall or ceiling needs to be opened to make the repair, drywall repair and painting. Comparing estimates from three licensed plumbers is the only way to really know.

  11. Nicole T August 9, 2016 at 1:12 pm - Reply

    Hi Bob,

    I came across your article and I’m wondering if you can help me and my fiance. We bought a house 11 months ago and twice we have used the spray silicone to cover a crack in a tile near the tub spout. This was found to leak through the trap in the second family room we have on the bottom floor of our split level. The first spray held us off for a good 6-8 months. Recently, we had to do another coat. Very recently, I thought my cat was urinating in the shower, as it spelled just like cat pee. I kept the sliding doors closed, but it wasn’t going away after multiple showers. I did a vinegar and baking soda bomb in the drain and across the floor of the tub. A few days later it’s even MORE pungent… We know we have a leak, but why this odor?!? We really are not in a position to do the bathroom over right at this time, as we are getting married in 5 weeks… Please help!!

    • Bob Jackson August 10, 2016 at 8:01 am - Reply

      The odor is caused by mold & mildew in the wall or subfloor due. A crack in the wall tile can be sealed with caulk as you’ve already done but the symptoms suggest a leak in the plumbing is the real culprit. You’ll need to inspect the plumbing to see what’s really happening. A snake inspection camera can be inserted through a small hole drilled in the drywall to locate the leak:

  12. William August 31, 2016 at 2:18 pm - Reply

    Great site
    I have checked all the plumbing and nothing is leaking.
    My problem stems from poor drywall installation and poor support behind the tub surround. As soon as we run the shower and the person is over 180 lbs water runs down the back of the tub.
    I used caulking silicone based to repair it before but it continues?
    I have a large access panel. How or what do I use to add extra support for the juccuzi tub and the drywall? Without tearing out the old tub surround and the old dry wall?

    • Bob Jackson August 31, 2016 at 10:01 pm - Reply

      Fiberglass bathtubs and surrounds require extra support by closely spaced wall studs (e.g. 14-1/2 inch O.C.), extra corner studs and/or horizontal bracing between the studs. Otherwise the tub and surround isn’t properly supported, causing it to flex and bow under the weight of an adult opening the seam and leaks.

      I can’t think of a satisfactory quick fix because the surround overlaps the tub flange and has to be torn out to add 2×4 supports and fasten the tub. May as well remove the surround, drywall and install additional studs per the manufacturer’s instructions.

  13. Deb September 12, 2016 at 10:26 am - Reply

    Help please. I have a tub and shower combination. When anyone takes a shower I am getting water coming through my ceiling. It’s not just dripping it is streaming.

  14. Brig September 19, 2016 at 10:59 pm - Reply

    I am having an issue where my shower will leak to the downstairs ceiling. It originally looked like it could be from the drain calking corroding, so I calked the drain. I then poured water in the shower and drain to test and there is no leak. But when the shower is turned on and running the leaking appears. Is it possible it is leaking in the shower handles? Do I need to cut a hole in the drywall behind them to examine? Or should I cut a hole in the ceiling to examine?

    • Bob Jackson September 20, 2016 at 9:02 am - Reply

      Start with a non-invasive approach: Remove the shower handle and escutcheon to check for leaks around shower valve and pipes. Do not remove the shower valve cartridge unless you find it’s leaking. You might see water dripping from above indicating it’s coming from the shower arm elbow or maybe at the shower valve.

      If you don’t see a leak at the shower valve then cut a small access hole in the drywall behind the shower. Opening the wall is way more convenient than the ceiling and covering the hole with an access panel is more natural looking.

  15. Debbie December 13, 2016 at 4:48 pm - Reply

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  16. Isiah Briggs March 3, 2017 at 6:35 am - Reply

    I think your pictures are great , they show you just what to do ! Thank you !

  17. Joann June 23, 2017 at 6:56 pm - Reply

    shower leaking through ceiling next to wall/ placed funnel in drain pored water through drain/ no leak// sealed around drain with silicone/ p0red buckets of water onto shower pan/ no leaks/removed shower spout taped and placed new one/ no leaks/ removed divert er cover/ saw no leaks/ or wet pipes// water comes through ceiling when the shower is turned on// Any ideas where to look next//

    • Bob Jackson June 23, 2017 at 7:48 pm - Reply

      Saw an access panel in the drywall. Because the shower drain doesn’t appear to be leaking the source is probably on the supply side but you couldn’t see it with the diverter escutcheon off.

  18. Mark Amo September 19, 2017 at 7:08 am - Reply

    Wonderful tips. Thanks for sharing!

  19. Mark KAy November 4, 2017 at 2:36 am - Reply

    I have a 1920’s house with the entire 2nd floor bathroom done in those plastic beveled tiles a little bigger than 4×4 inches (I think) that use no grout. The bathtub/shower has 3 knobs, for Hot, Shower and Cold. The ceiling tiles on the 1st floor sagged and came down from a leak somewhere. I thought I saw water dripping–not dripping into the tub, but instead it followed the spout back to the wall. So I tightened the knobs and siliconed entirely around where the tub met the wall. I replaced the ceiling tiles and thought everything was fine. There is no access panel, just a door about 10×36″ for towel storage.

    I thought this was fixed but it’s about 3-4 years later and the ceiling is sagging again, enough to open the seam between the 12×12″ ceiling tiles. Now I notice that about 10-15 seconds after turning EITHER water knob on, water starts slightly trickling from only the Hot knob, near the wall. My neighbor, who was a great handyman but has since passed away, told me to turn the water off in the basement where the shutoff is, and remove the screw and the Hot knob, but I forgot what else to do! Does this sound correct if the water leaks only out of one side, regardless of which valve is turned on? Is this considered the packing, or the mixer valve? Can you give me the proper procedure? I’m alone & handicapped and it’s hard getting around across 3 stories/floors. Sorry for such a long post, I just think it’s better to include as much details. Thanks for any help!

    • Bob Jackson November 4, 2017 at 2:23 pm - Reply

      Most likely the washer on the hot water valve is worn out. Try replacing the hot & cold valve stem washers. Replace both because they’re equally old. See these videos:
      * How To Fix A Leaking Bathtub Faucet Quick And Easy
      * Shower Faucet Repair (thorough step by step.)

      Worst case the shower/tub valve may need to be replaced, see Shower Valve Replacement. For that you’ll need to call plumber.

      • Mark KAY November 7, 2017 at 3:23 pm - Reply

        Thanks for replying! I found a bunch of rubber washers, only 1 was flat, the rest were domed; the handles say GENERAL on them, the screw goes right through without any plastic cover. Anyway, I removed the screw but the handle is stuck; the bezel/escutcheon/tube behind it is one piece and I started unscrewing it and it appears that it threads easily but before it bottoms out on the back of the handle, it looks like when I turn it, the stem is unthreading with it! The nut isn’t moving, just the threaded stem. Does this seem correct? I hope I don’t have to get a puller or slide hammer. I’m only working on the HOT side that was leaking so far.

        • Bob Jackson November 7, 2017 at 7:29 pm - Reply

          You’ll need to buy a faucet handle puller tool. The Cobra PST168 Faucet Handle and Compression Sleeve Puller Kit and fits a wide variety of handle sizes. Home Depot has a faucet puller tool that should also work.

          See this YouTube video showing how to use a faucet puller tool.

          You don’t want to hammer or yank on the handle because it will stress the plumbing.

          • Mark KAY November 8, 2017 at 3:11 am - Reply

            Thanks for all your help and instruction, Bob! Turned out it was a pre-1940’s CENTRAL brand, NOT General. H-D had nothing (just the puller) they couldn’t get the slotted screw off the seat washer but they gave me a lead, Ed Young’s Plumbing in Williamsville, NY; I got there at 8:55pm and left there at about 20 minutes past closing with my stem newly repacked and a stubborn screw & seat washer replaced, plus a 2nd seat washer for the cold side, and the large o-ring type plastic washer between the seat & stem large nut. Total cost $6.27! I have never seen [on Youtube] a 1-piece chrome sleeve/escutcheon that threads onto the stem, neither did the 2 guys at H-D! The large nut is actually outside the wall and the chrome sleeve screws up against the wall & covers everything. Returned the puller and bought a cheap 12-inch adjustable wrench for $6.99 plus I had a 20% off coupon (Harbor Freight.) THANKS AGAIN!

  20. Problem Solver December 17, 2017 at 4:50 am - Reply

    I have a problem in my shower stall. Shower faucet handle is very difficult to move, after researching I believe the cartridge needs to be replaced. This is a new faucet put in by a plumber two years ago. At the time, it was not installed properly resulting in a serious leak into my dinning room on the main floor ceiling and wall. Plumbing company repaired it, I was thankful. A few weeks ago I started seeing paint slitting on the same ceiling area that occurred after the original problem. Plumbers left a hole in my linen closet next to the shower stall where they accessed the faucet to do the original repair so I went up and checked and pipes are dry, after shower use. My dad and I inspected and saw a small crack in the drain pipe on the floor, so silicone cauking was applied. I thought problem solved. Sadly, I continue to see more cracking in paint in the ceiling which I suspect means there continues to be water leaking somewhere. My question is ….it possible that water is leaking inside the wall from the stuck faucet/ cartridge? Can water not totally be shut off even though I do not hear a drip? Plumbing company is coming out Tuesday. We have not been using the shower for a week now. I am frustrated and wanting to be prepared for the appointment Tuesday. Is this a result of the original repair? This is getting to be an expensive problem. Appreciate any advice or insights.

    • Bob Jackson December 18, 2017 at 11:53 am - Reply

      > My dad and I inspected and saw a small crack in the drain
      > pipe on the floor, so silicone caulking was applied.
      That would be a shower drain leak, see How to Fix a Leaky Shower Drain. Based on your description, the drain flange is cracked and it’s worked loose causing a leak at the gasket under the shower pan. A leaky drain is unrelated to the shower valve repair.

  21. Brenda February 15, 2018 at 9:24 pm - Reply

    I noticed my closet behind the bath tub
    was getting wet as well as the outside
    wooden wall. I thought it my be a leak
    behind the drain.
    I started using another showet. until i
    can get the one with the leak fixed.
    Using the other shower causes the leak
    as well…
    Probably because its routed to the line
    the first bathroom which is routed to
    the sewer line in the back of the house…
    The house has had foundation repairs
    and the plumbing has been rerouted…
    i going to start on it soon…
    Any opinions from you would be helpful…

    • Bob Jackson February 16, 2018 at 5:05 pm - Reply

      First step is to cut an inspection hole in the closet wall behind the tub to determine if the leak is coming from the water supply lines or drain pipes. The pipes and joints may have been stress or bent when the plumbing was rerouted during the foundation repair. A small hole can be drilled in the wall to insert a snake inspection camera for minimal disturbance as discussed in my previous comments to other readers.

  22. mike April 11, 2018 at 7:35 pm - Reply

    great article. But in our situation, we cannot access the back of the shower — the front of the shower is an outside wall, not another room/closet. SO how will we examine the scene?

  23. mike tomecek April 11, 2018 at 9:33 pm - Reply

    One thing that s/b done first is to make sure there is an comprehensive adequate seal in the bath-shower stall where ver water hits wall or otherwise preeable surface where it can leak behind. we have a shower leak and we put plastic on the side of the tub that was getting the leak that we saw on the first floor and so far tests have shown no leaking. I had recently re-caulked and I bet there was a spot that was not sealed properly — I cd push the plastic wall a bit and see some daylight in the area of the leak and I wonder if this is the cause. The other possibilty is the spray direction. We cleaned the front of the shower head which was full of minerals and it now produces a cleaner spray which does put pile up water in the corner w/ the dubious caulking. so it cd be a twofer pair of causes here.

  24. Annie June 5, 2018 at 11:56 am - Reply

    There is a wet area in my bedroom where the shower wall abuts my bedroom wall. It is only wet in the corner, on the floor, not on the wall . We stopped using the master bath shower and the leak dried up. We went back to using the bathroom and it it got wet again. it took a few days to become obvious, I guess this means a very small, slow leak. I live in Florida so my house is concrete block on a slab. The house is 7 years old and i think it has been leaking for a very long time.Where should I cut the hole? At the floor like you show, or higher up, the level of the on/off valve? I have had a general handyman and a plumber come look at it but not cut the wall. One said the grout must be leaking, the other said the house did not appear to have a plumbing leak. I have a wet corner and have pulled up the carpet and see water staining on the slab. Your thoughts? Thank you. (the shower floor is a step down, not level with the rest of the house)

    • Bob Jackson June 5, 2018 at 6:27 pm - Reply

      I had a house in Florida on a concrete slab with concrete block walls. It also had a step down shower pan about 3 inches lower than the house slab. When I remodeled the master bath I discovered the shower pan did not have vinyl liner. The vinyl liner should go up the wall about 8 inches above the shower floor and behind the cement backer board. This prevents leaks through the grout joints which will seep under the moisture resistant drywall or cement backer board along the base of the pan.

      You can see where the paper face of the insulation has gotten wet at the base of the shower floor in this photo. I’d already torn off the drywall which was wet and crumbling along the bottom. The seepage was small enough that it didn’t run under wall.

      There are several ways you can verify water is leaking through the tile grout joints:
      1 – Cut an inspection hole in the drywall on the opposite side of the shower wall closest to the leak.
      2 – Or grind out the grout joints around a wall tile near the shower floor, then chip/break out the tile.
      You may find the moisture resistant drywall is soggy, or cement backer board is damp depending on construction. If soggy drywall, cut it out to see if there’s a shower pan liner behind it. Probably not. If you have cement backer board, drill a 3/4 inch hole to see what’s behind it. Vinyl liner or maybe nothing.

      If there’s no vinyl liner the fix is to either:
      A. [OK] Tear the tile and backer material off the lower 3 feet of shower wall; install cement backboard, new tile and seal the grout with grout sealer. You’ll need to reapply grout sealer every so often to water proof it. Given the difficulty of matching old & new tile, you may end up tearing out all the old tile wall.
      B. [Best] Tear out and rebuild the shower pan & wall with a vinyl liner. The Schluter®-KERDI-SHOWER-KIT is a great product.

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