How to Diagnose a Leaky Shower

Learn how to find out if that leak is really coming from your shower and exactly where and what may need fixing

Drip, drip, drip. It's one of the most irritating sounds in the world, but you're actually lucky if you can hear it. Leaks can happen anywhere, and there are plenty of places out of earshot. Just knowing that there's a leak is half the battle: you know there's something that needs fixing. The quiet types, though, can drip away for years in the muffled darkness of your walls and floors, threatening the wood as well as your wallet.

Showers are a common source of leaks, some of which can be difficult to pinpoint. If you've noticed a drip from the showerhead, damp spots on a wall, or stains on a ceiling below, it needs to be addressed: even a seemingly insignificant leak can waste a shocking amount of water over time, and extensive water damage doesn't require much. For more mysterious leaks, the various components of the shower need to be tested independently to hone in on the cause. When the source isn't apparent, it may not even be the shower, though all evidence might point to it. Leaks could be from the toilet, or plumbing in a completely different area - but it does help to eliminate what's moving the largest volume of water.


Finding the Leak

The first step? You must unlearn what you have learned. Well, sort of. Whenever we come upon a leak, we can't help formulating a theory about its origin, which is fine, but not necessarily helpful. The thing with water is that it travels easily: a leak originating in one spot can run along pipes and boards many feet, pooling in a completely different and misleading area. So wherever you see that puddle or stain, don't assume the actual leak is directly above or even nearby; start investigating.

That being said, there are cases where it's fairly obvious what's going on. If you have a wet floor after showering, take a good look at the caulking on the shower door. Close it, and spray water along the track and each corner to check for problem areas; go for at least a few minutes, in case yours is a slower leak. Should the leak be discovered, recaulk the door. Also take a look at the subfloor and any ceiling below, since it could be moldy or otherwise compromised if water made its way into any gaps at the base of the shower. If this looks to be the case, recaulk between the base and floor, as well.

Similarly, a leak coming out of the showerhead is unmistakable. These can be caused by limescale and other deposits clogging the spray holes, forcing water out of other openings. If yours is looking a bit crusty, cleaning it should help. Take the head off the arm so that you can also take a look at the O-ring inside, another common culprit (try to locate an owner's manual to find out how to properly take apart the head). If the O-ring looks a little rough, replace it. Make sure to apply new PTFE plumber's tape when you reattach the head to its arm.

Other times, a leaking showerhead is due to worn components in the valve. If cleaning the head and replacing the o-ring don't cut it, your next step would be to replace the stems or cartridges, and any compromised washers inside the valve. We have a handy DIY article for this procedure (though this deals with sink faucets, it applies to showers as well).

Sometimes, though, you don't get away that easy. Sometimes, you have a random stain on a ceiling. Or a damp spot, or a musty odor. If this is how your leak is presenting itself, there are a few possible sources, and it will take time and attention to pin it down.

One of the easiest spots to check first is around any escutcheons. When they're not properly sealed against the wall, it's easy for water to run down into gaps and move well beyond. You might notice loose tiles or discoloration in the general area; if no waterproof membrane was installed with the shower, stains or wet spots on the adjacent wall or a ceiling below could be from here, as well.

Some escutcheons come with a gasket – you'll want to replace this if it's no longer forming a tight seal. If your escutcheon doesn't have a gasket, use silicone caulk or plumber's putty to seal it against the wall. When resealing, leave a gap at the bottom of the escutcheon to allow any moisture that might get in a way out.

Is anyone in your home short or tall enough to have to adjust the showerhead each time they get in? That kind of regular movement can loosen the arm from the riser pipe, generating a leak that can drip down the plumbing behind the wall. If you have evidence of a leak on this or the adjacent wall, or a ceiling below, it's worth investigating. Remove your showerhead from the arm, and screw on a cap in its place. Remove the escutcheon(s) covering the valve, and run the water. The pressure from the capped end should expose any leak between the head and valve in fairly short order. Try reinstalling both the shower arm and head with a fresh wrapping of plumber's tape.

Are the walls of your shower tiled? As beautiful as it may look, that could be distracting you from a dark, destructive secret: cracked grout. Take a careful look at the corners of the shower, all the way up the top. Any cracks you see could be allowing water to move behind the wall, unobstructed, to do what it will. Newer showers may have their waterproof membrane going up the length of the walls to safeguard against these kinds of leaks, but unfortunately, most showers and tubs weren't installed with such foresight. Take out the cracking grout up the corners, and replace it with silicone or tile caulk. If you're worried about looks, caulks are available to match many grout colors.

Believe it or not, drains, too, can have a few things go wrong that will result in leaks. To check yours, remove the stopper, and either run a length of hose from the bathroom sink straight into the drain, or use a bucket. If you don't have a way to check directly underneath the bathroom (eg. a basement, crawlspace, or access panel in the adjacent wall/ceiling), you'll have to open up the wall or ceiling to look for the leak. Try to have someone walk around in the shower while you're checking: some leaks won't manifest until weight flexes the pan (plastic and fiberglass shower pans are especially prone to this).

Should you spot the leak, it's likely either a deteriorated or damaged gasket between the drain assembly and the shower itself, or a cracked flange. Replacement of both are addressed in our DIY guides for removing and installing a drain flange. If a whole new drain is in order, consider a WingTite drain, or Davke's Dream Drain, for quick and easy installation.

Maybe the drain looks good. That's good news, right? Right. So try to bask in that for a minute, because the final thing to check is also the most expensive and disruptive to fix: the shower pan. Pre-fabricated pans can crack, and the membranes in traditional pans can be punctured during and even after installation. The test for a compromised shower pan is not particularly involved, but can be excruciatingly long, so you'll need to plan accordingly.

Plumbers usually use a fancy rubber plug to stop the drain. They can be fairly inexpensive, depending on the style, but you can also get away with duct tape. Use plenty, and cover the drain completely, going out at least 6" from its edge. Once sealed, fill the shower up to about 1-1/2". In theory, a properly installed and operating shower should not lose any of that water. You could mark the level with a bucket or a stack of coins, but nothing beats visual confirmation of a leak (after all, the tape could loosen, or the dog may wander by and sneak a gulp). Then, you wait... for a very long time. The bare minimum is 8 hours, but some leaks haven't been discovered until hour 50 of a 3 day test. It's up to you how thorough you want to be, and that will likely be based on the amount of damage you've been able to find. Just keep in mind that the pan membrane is the last line of defense, and in a properly installed shower, leaks drip down to it, following its slope into the drain, away from the innards of your home. So it's kind of important.

Note: This test does not check the curb of the shower, which may or may not have that waterproofing membrane extended over it. If you notice discoloration or moisture on or around the curb, it may be due to a missing or damaged membrane, and could indicate serious water damage.


And with that, we've come to the end of the line (as far as the shower goes). With any luck, you've discovered the source of the leak, and arrangements have been made for its repair. You're happy, and your house is safe for years to come. True, with a shower pan replacement, you might be paying a pretty penny for that happiness, and it may not actually be happiness yet, but don't worry: it will come. You'll hear about somebody who let their leaks go and got a broken house in return, making your few thousand dollars a mere drop in bucket, comparatively. Leaks don't usually go away on their own, so unless the house is going to be abandoned, they'll need to be dealt with sooner or later… and what argument is there for later?


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