Shower Drain Leaking Into Basement: Causes and How To Fix

That dripping coming from the ceiling in the basement is enough to raise any homeowner’s blood pressure. If left unchecked, leaky plumbing can cause a home’s frame to rot or mold to form. And, with some plumber’s charging upwards of $200 an hour, fixing a shower drain leaking into the basement can be a significant expense.

Fixing a shower drain leaking into the basement is often a simple repair that the average homeowner can tackle himself with basic tools and a few inexpensive plumbing supplies.

In this article, we’ll discuss how to identify the source of a leak coming from the first floor shower drain. We’ll also provide instructions for how to fix that leak once you’ve determined where it’s coming from.

Shower Drain Leaking Into Basement

Why Is My Shower Drain Leaking Into the Basement?

To fix a shower drain leaking into the basement, the first step is to figure out exactly where it’s coming from. The leak could be coming from the drain flange or the rubber gaskets that create a watertight seal between the drain and shower pan. Sometimes the leaks do not come from the drain at all. A leaky P-trap under the drain or a cracked shower pan could also be the culprit.

Leaks can also originate from damaged bathroom tile or even a leaking shower faucet. In this section, we’ll cover how to identify exactly where that leak is coming from, so you can proceed with the necessary repairs.

1. Leaky Drain Pipe

The leak may not be coming from the shower drain itself but rather the drainpipe that runs from the drain to your home’s main drain pipe. Like the drains in all the sinks, tubs, and showers in your home, a shower drain runs into a P-trap, the curvy pipe just below the drain.

The P trap holds water in the pipe when the shower is not in use to prevent smelly sewer gases from entering the home. The plumbing connections between the P trap and the drains are common places where leaks can occur.

Checking the P-trap for a leak is a relatively easy process. First, head to the basement and wipe residual moisture from around the drain and the P-trap. Turn on the shower and observe the P-trap’s two lock rings. If water begins leaking from either of these connections, the leak is coming from the trap.

2. Cracked Shower Drain Gasket

Shower drains have rubber gaskets between the drain and the shower pan. These rubber gaskets are responsible for creating a watertight seal between pan and drain. Over time, these gaskets can eventually dry out and crack, especially if the shower is not used very often.

When the rubber dries out, the gasket ceases to do its job, allowing water to pass through the seam between the drain and the shower pan.

If you suspect the water leaking from the drain is coming from the connection between the drain and the shower pan, then check the gasket. Make sure the shower is off and there is no water in the pan.

There are two methods for removing the drain depending on the drain style. Some drains screw directly into the shower pan. For this style, remove the cover from the drain using a screwdriver.

Next, remove the drain using a drain wrench or locking a pair of vise grip pliers onto the drain. Unscrew the drain by turning counterclockwise.

For plastic shower pans, remove the shower drain by unscrewing the lock ring from the shower pan from the basement side.

Once the drain is removed, check the rubber gasket. If it appears dry and cracked, then the drain gasket has failed and must be replaced to stop the leak.

3. Damaged Shower Pan

Identifying a leaky shower drain takes more work. Since it’s difficult to see cracks in the shower pan, you’ll need to fill the shower pan with a few inches of water to identify it. As most showers do not have a shutoff for the drain, you’ll need to remove the drain cover and plug the drain.

Once the pan has a few inches of water in it, head to the basement to see if you can spot the leak. You may have to wait a while as shower pans can often take a while to leak. Leave the water in the drain pan for eight hours as shower pan leaks can take a long time to become visible.

Often, cracks in a shower pan only open when the pan flexes under the weight of an occupant, so you may need to have someone stand in the shower while you check for a leak.

You can also check to see if the water level in the shower pan is falling to determine if you have a leak. Once you’ve located the leak, you can move forward with a repair.

4. Leaky Drain Flange

A drain flange is the metal piece on the drain that overlaps the shower pan. There is typically a layer of plumber’s putty between the flange and the pan that creates a watertight seal, preventing the water from leaking below.

Water may also be leaking between the threads of the shower pan and the drain.

A leaky drain flange is one of the easier leaks to identify. To test for a leaky drain flange, plug the drain using the method described above, then fill the drain pan with water. Once filled, go to the basement and check the area around the drain for water. If you spot water leaking from the drain’s rim, then the putty seal between the flange and pan has failed or the drain has become partially unscrewed.

5. Leaking Shower Faucet

Sometimes the leak may not be in the drain at all. Sometimes it’s the shower faucet. A leaking shower faucet can cause water to run If you check in the basement and water is not coming from the drain; then chances are it’s coming from the shower faucet.

If the faucet is leaking, water will typically travel down the supply lines and drip to the floor near the drain. A leaky faucet typically indicates a bad connection between the shower faucet and the supply lines.

If this is the case, repair immediately. Unlike a drain that only leaks when the shower is in use, a leaky supply line will leak whether the shower is in use or not. Such a leak can quickly create major problems in the framing below, not to mention raise your water bill significantly.

6. Damaged Bathroom Tile

Bathrooms have tiles that are designed to prevent water from passing through them. This protects the subfloor should water escape the shower while someone is showering or when some carry water with them while exiting the shower.

However, if that tile is damaged, then water can pass through the tile and reach the subfloor, eventually saturating it, causing water to leak below through the basement.

If the leak does not appear to be coming from the drain or the shower, but rather the subfloor in the basement, then check the tiles above for cracks. Water that breaches the tiles can cause the subfloor and frame below to rot, so it’s crucial that it be fixed as soon as possible.

How Do I Fix a Leaking Shower Drain

Leaking shower drain

A shower drain is a relatively simple thing to fix but does require some knowledge of how a drain works.

A shower drain consists of the drain that fits into the hole in the shower pan. The drain typically has threads that screw into the hole. A rubber gasket fits between the drain and the pan to create a watertight seal. A strainer over the top of the drain catches larger particles before they’re allowed to enter the drain to prevent clogs.

After the water passes through the drain, it enters a P trap before beheading to your home’s main drain. This trap allows water to remain in the part of the drain pipe and serves as a barrier that prevents sewer gases from entering the home through the shower drain.

To remove the drain, you’ll need to begin by removing the stopper, which can be completed by simply unscrewing it, turning it counterclockwise. Once the stopper is removed, you’ll be confronted with the drain basket.

Removing the drain basket typically requires a tub wrench. A pair of locking pliers will also work. Turn the drain basket counterclockwise to unscrew it from the tub.

Some shower pans have a lock nut that attaches to the drain below the shower pan. In this case, you’ll need to loosen this nut from the basement side to remove the drain.

Repair Shower Drain

If the shower drain is leaking, it’s either between the threads of the pan and the drain or through the flange.

A leak between the threads is caused by a lack of plumber’s tape used to seal threads in plumbing connections, so they don’t leak.

Repairing this type of leak is typically a pretty simple fix. Once you have removed the strainer per the above instructions, clean off any old plumber’s tape from the threads. Wrap the screw threads in a fresh plumber’s tape, making sure to cover the entire circumference of the drain.

Screw the drain back into the tub. The plumber’s tape will create a water-tight seal between the threads of the tub and the flange, preventing water from passing through.

If the leak is coming from the flange, you’ll need to replace the plumber’s putty between the flange and the shower pan. Remove the drain, then scrape off any old plumber’s putty. Roll fresh putty into a snake shape and apply it to the entire circumference of the flange.

Screw the drain into the shower pan, then give it an extra quarter turn with a drain wrench or a locking pliers to make sure it tightens into place and creates a tight seal. Make sure not to over-tighten as it could crack the shower pan. Remove any excess putty with your fingers.

Replace Shower Drain Gasket

A rubber gasket is responsible for creating a water-tight fit between the connection of the drain and the drain pipe.

Sometimes this rubber gasket will become dry and cracked, especially if the shower is rarely used and the rubber is allowed to dry out. After removing the drain cover and the flange, carefully remove the rubber gasket using a pair of needle-nose pliers.

If the gasket is dry or cracked, it’s likely allowing water to flow through. Use the old gasket to help you purchase the proper size for a replacement. Before installing the new gasket, remove any debris caught between the drain pipe and the drain.

Next, palace the rubber gasket over the drain pipe, ensuring that the bevel side is up. Push the gasket down until it is at the bottom of the drain opening. Replace and tighten the flange and attach the drain cover.

For shower pans with a drain that threads directly into the pan, the gasket will be located between the rim of the drain and the surface of the shower pan. After removing the drain, pull the gasket off the threads and replace it with an identical new gasket.

Add plumber’s tape to the threads, replace the drain and tighten it to compress the new gasket and create a watertight seal.

Fix Damaged Shower Pan

Fiberglass, acrylic, and plastic shower pans are much easier and more affordable to install than ceramic tile bases that require mortar and some skill to set them at the proper angle. They do have their downsides, though. They aren’t as strong as ceramic shower pans and can sometimes crack, causing a leak.

Since these cracks are often only visible when the pan flexes under the weight of an occupant, they can be difficult to find. If the cracks are relatively small, it’s feasible. Larger cracks will require you to replace the entire shower pan.

To fix a small crack, you’ll first need to purchase an acrylic repair kit. Clean the area using household cleaner and a cloth, then remove any debris in or around the crack. Apply the putty or paste to the crack using an applicator stick or putty knife. Some repair kits may require you to mix a hardener and resin before applying.

Smooth the area using the putty knife or stick, so it’s flush with the rest of the shower pan. Allow the paste to cure based on the manufacturer’s instructions, then sand smooth with a fine-grit sandpaper. Use a cloth to polish the repair to a smooth finish.

Fix Leaking Shower Drain Pipe

Sometimes the leak coming from the drain of the shower isn’t the drain at all but rather the P trap that runs below the drain. This trap is curved, so it holds about a cup or so of water that creates an airtight seal.

A typical P trap has two connections, one end connects to the drain pipe and the other extends horizontally to the drainpipe that leads to your home’s main drain and the sewer.

Both connections cuffs that screw onto the P trap, creating a compression seal with both drain pipes. If these cuffs were not properly installed or have loosened over time due to the flexing of the shower pan above it could compromise the seal, causing a leak.

Often, fixing a P trap leak is an easy fix. Use a plumber’s wrench to tighten the locking rings a quarter turn or so to increase the pressure on the seal. If this fails, the seals in the compression fittings may have failed. In this case, you’ll need to replace the entire P trap.

To remove the P trap, simply loosen both locking rings. Make sure to have a towel or cup on hand to catch the water in the P trap. Take the old P trap with you to the store so you can purchase the right size.

To install the new trap, thread the drainpipes into both ends and tighten both compression rings by hand. Use a plumber’s wrench to tighten the rings an extra quarter turn, taking care not to overtighten the rings, which could damage the fittings.

Why Is It Important to Repair a Leaking Shower Drain Right Away?

While it may be tempting to wait on repairing a leaking shower drain, especially if it’s a relatively minor leak, don’t. If left unchecked, a minor leak can cause major damage to the structural framing underneath the shower.

This could quickly escalate the problem from an inexpensive minor repair to an expensive major one. The water will leak onto the framing below, causing rot. It can even create a mold problem that can impact the air quality throughout your home.

Conclusion

While water dripping into the basement from the shower above can cause alarm, it’s typically a repair that most DIYers can handle with basic tools and minimal expense. Unlike repairs to showers in the upper level of a home, repairs on a lower level are easier because they allow easy access to the plumbing from the basement below.

By following some simple steps, you can identify the problem and fix it, and have your shower back into service. Whatever the cause of the leak is, it’s crucial not to put it off. Delaying a leaky shower that still sees regular use can cause water to saturate and rot the framing below the shower, causing serious structural damage and an expensive repair bill.

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