Three fixes when a shower leaks but not the tub

Last Updated on March 13, 2021 by Dave Farquhar

My sons have to take baths because their shower leaks but the tub doesn’t. I talked it over with a plumber, who kindly shared three relatively easy and cheap fixes for when a shower leaks but not the tub. In my case, the shower leaks into an unfinished basement utility room and not a finished ceiling, but in either case, you want to either fix the leak or not use the shower. Leaks lead to water damage and mold, and you don’t want those things.

My local plumber’s suggestions are to replace the faucet, caulk around the faucet and the overflow plate, and shore up the caulk between the tub and the surround. If the shower leaks all the time, it’s more likely to be the faucet. If it leaks just when certain people use it, the problem is more likely to be caulk. In most cases you can fix it yourself in less than an hour with less than $30 worth of materials.

Replacing the faucet when a shower leaks but not the tub

shower leaks but not the tub
If your shower leaks but not the tub, replacing your faucet is a good first thing to try. Replacing my 32-year-old faucet with this one solved my problem. It took less than 10 minutes and trust me, this one looks a lot nicer than the old, worn-out one. If I’d known it was that easy, I would have replaced the old one years ago.

My faucet was made by a company that went out of business in 1987, so it was probably due for replacement. That doesn’t seem that long ago to me, but 32 years is a good run. Replacing a faucet is something that looks hard if you’ve never done it before, but it’s much easier than it seems. And replacement bathtub faucets generally cost around $20.

The diverter on bathtub faucets does wear out over time. When you use the shower, it forces a lot of pressure behind the diverter, and if the diverter is worn out, it can direct water incorrectly, including into the wall behind your shower, where it leaks into the floor below.

Removing the old faucet

Most faucets have a set screw that holds them in place, either on the side or on the bottom. If you don’t see one on the side, look on the underside of the faucet. You can use a mirror or your phone’s camera to make this easier. In my case all I found was a bunch of nasty mineral deposits. That told me the faucet has been leaking.

If you have a set screw, loosen it. Usually set screws on the side loosen with a flat bladed screwdriver and set screws on the bottom loosen with an Allen wrench. After you loosen the set screw, the faucet slides straight out.

If yours doesn’t have a screw at all, like mine, just turn the whole faucet counter clockwise. I used a monkey wrench to get more leverage, because mine didn’t want to move after about a quarter turn. Don’t crank on it because you don’t want to strip any threads or break a pipe. When I put my wrench on it, my faucet turned without a great deal of effort.

Take your faucet with you to the hardware store or home center to get a replacement. You want a replacement that attaches the same way as your old one. Also pick up a spool of PFTE tape if your faucet attaches via threads rather than a set screw. Your faucet may or may not come with it.

You may also want to get yourself a tube of clear bathroom caulk, as a preventative measure.

A temporary fix

A temporary fix that sometimes works is to run your faucet through the dishwasher to blast out whatever gunk is inside it, then soak it in vinegar for a few hours to dissolve any chemical deposits that are inside. You’ll usually end up having to replace the faucet anyway after this, and it’s probably faster and easier to go to the store and buy a new one than to clean the old one and replace it. My research indicated this could work and I tried it.

But look at this as a way to put off a $20 purchase until your next paycheck, not as a long-term fix.

Replacing the faucet

Assuming you bought a faucet that connects the same way as your old one, take your replacement home and attach it. In the case of a set screw-type, slide it onto the pipe, then tighten the set screw. Don’t overtighten because you don’t want to damage the pipe. That turns a cheap repair into an expensive, time-consuming one. Tighten the screw just enough that you can’t rotate the faucet.

If your faucet screws on, clean off the threads with an old toothbrush. Once they’re clean, put a turn of PFTE tape around the threads. This helps seal them and give you a tighter fit. Then place the new faucet on the threads, give it a clockwise turn or two to make sure it caught, then tighten it down. Get a good tight fit, but don’t overtighten. The point where it won’t go on any further probably will leave it facing a weird direction, so turn it back counterclockwise until it faces down.

The universal one I got can connect at least four different ways, but it didn’t fit right out of the package. Read the instructions with your new faucet, especially if you get a universal one.

Using caulk to fix when the shower leaks but not the tub

The plumber asked if the problem happens all the time, or just when certain people take a shower. He said different people stand in different places, and that affects what the water does.

Caulking the spout and overflow plate to stop shower leaks

He suggested applying some clear bathroom caulk around the spout and around the overflow plate. Water hitting the wall of the shower can flow down and find any gaps in there, then eventually find their way down to the floor below. Caulk in a squeeze tube will give you a little more finesse than a caulk gun. Just apply a thin bead of caulk around the faucet and plate where they meet the wall, seal it down, then wipe away any excess.

If your spout and/or overflow plate have mineral deposits on them and you don’t want to replace them, and you also don’t want to immortalize the deposits in caulk, here’s an easy fix I’ve used in a few houses. Soak a paper towel in white vinegar. Put the towel over the mineral deposits and let the towel sit a good 15 minutes. When you come back, the mineral deposits will probably either wipe off or scrape off. Then they’ll look good enough that you can caulk them.

Caulking the shower surround

He also said to look at the caulk line where the top of the tub meets the shower surround, if it’s a one-piece surround. Water getting into that gap can also leak down onto the floor below. Either shore up the caulk, or better yet, remove the old caulk and re-caulk it.

If you have a tiled wall, he said that can be tougher. If you can find any spots in the grout that look problematic, patching those can help. But a leak in a tiled wall may require professional help if the other fixes don’t work.

Related questions

Much like fixing basement seepage or a leaky basement wall, when a shower leaks but not the tub, it looks like a bigger problem than it is. But it can still raise some other questions.

Shower leaking in or behind the wall

The most likely cause for a shower leaking in the wall or leaking behind the wall are the same things I listed above, plus possibly a poorly installed shower head. Check to make sure that the shower arm (the pipe that extends out of the wall that attaches to the shower head) is tight. If it’s tight and still leaks, remove the arm and make sure there’s PFTE tape on the threads. You might consider cleaning off the pipe, applying new tape, and replacing the shower arm and/or shower head. If those fixtures are dated, this can be an excuse to update them.

If you end up replacing the shower head and the shower arm, it can turn this into a much costlier project. But it’s also a quality of life upgrade, and if and when you go to sell the house, clean and up-to-date bathroom fixtures are something that buyers notice.

Should you caulk around a tub faucet?

Water will find its way into any gaps. Looking at my old faucet, which wasn’t caulked, there were visible places where the water corroded the old faucet over the years. So in addition to closing off a source of water getting into your wall, caulking around a tub faucet will also make the faucet last longer.

It makes the next faucet replacement a more time consuming project, but that’s a minor sacrifice for the other benefits.

Does replacing bathroom fixtures increase the value of your house?

Don’t expect to spend $100 on upgraded bathroom fixtures, save your receipts, then expect to get $100 more when you go to sell your house. I had a neighbor try that once, and that didn’t go over all that well.

Replacing dated and worn fixtures even with inexpensive fixtures will make your house more appealing. The $4 plastic shower head won’t impress anyone, but a middle of the road option will at least make your house easier to sell. Plumbing fixtures are things people will notice when they look at a house, and some people have no idea what’s involved in changing them. If you take away that reason for someone to keep looking, you’re more likely to get that second offer.

I don’t recommend moving into a house and changing everything immediately. But if you can afford to make a modest improvement, it makes more sense for you to do it while you’re living in the house so you can enjoy it, rather than paying at move-out for bathroom upgrades for someone else.

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