Tub Faucet Leaks When Shower Is On: How To Fix It

When taking a shower, it’s usually preferable when the water comes out of the showerhead, not the tub spout. If you wanted to take a bath, you’d take one, so why is the water coming out of the tub spout when it should be pouring out of the showerhead?

This is a common problem in many homes – you turn on the shower, expecting a nice, toasty spray, only to find the water pressure lackluster and water pouring from the tub spout. So, how do you fix it? We put together a guide to help you navigate this process, so continue reading to learn more!

Why Does My Bathtub Leak When The Shower Is On?

Bathtub Faucet

If your leaky bathtub faucet is trying to steal the show during a shower by pulling water pressure, there’s likely one of three things happening. Some fixes are easier than others, but try these repairs before you call a plumber to wrangle the problem.

Partially Engaged Diverter

Sometimes, the problem is as simple as a partially engaged diverter. This happens when the little rod you pull up on is only partially in place, leading to a leaking tub spout. Inside the shower/tub setup, there’s a diverter, which directs the water to the tub spout or shower head (depending on how you work the mechanism).

So, if the rod on your tub spout is only partially pulled up, it might cause issues with water pressure during showers. Suppose you have a shower/tub combo featuring a different diverter-changing mechanism. In that case, the concept remains the same – if the valve is partially open, water will leak from the tub spout while you shower (or vice versa).

How To Fix It

If this is the culprit behind the issue, the fix is straightforward (it’s the easiest of the bunch!). When you turn on the water for the shower, ensure you pull all the way up on the rod controlling the diverter. Don’t crank on the rod forcefully – pull up firmly to ensure it’s in the correct position.

Mineral Deposits

Clogged Aerator

Hard water can cause a host of problems for the appliances and fixtures throughout your home. As the water evaporates in and on those fixtures and appliances, it leaves behind a special gift: minerals. These minerals appear as crusty, chalky white deposits coating various internal and external components.

Over time, these deposits can build up on the insides of pipes, faucets, appliances, and more, causing issues. So, as you might imagine, these deposits can wreak havoc on your tub faucet. Sometimes, these deposits build up in your showerhead, blocking the tiny water holes, which can cause water to leak out of the tub spout.

How To Fix It

Contending with mineral deposits isn’t a tricky process, but it is time-consuming. Luckily, you only need to participate in a small portion of the process (most of it is soak time). Here’s what you’ll need:

  • Plastic bag
  • Rubber band
  • White vinegar

To start, you’ll need to remove your showerhead. If it doesn’t easily come off, you can always tie a bag with vinegar to the showerhead. Either option works! So, if you’re removing the showerhead, fill a large gallon bag with enough vinegar to submerge the showerhead holes. Seal the bag (if possible), then let it sit for a few hours (preferably overnight).

Or, if the showerhead doesn’t easily unscrew from the shower arm, simply attach a bag with enough vinegar to submerge the offending area to the showerhead. You might need someone to hold the bag on the showerhead while you secure it with a rubber band, as it can be tricky. Once it’s on there, follow the same soaking instructions.

After a few hours or overnight, remove the bag from the showerhead and rinse the holes to remove debris. If the showerhead is still attached, do this by turning on the water. Or, if the showerhead is detached, simply rinse it in warm water.

Reattach the showerhead (if applicable), then check for leakage from the tub spout.

Failed Diverter Valve

Delta Shower Arm Diverter for Hand Shower, Chrome

In some cases, the problem isn’t so simple. Instead, the culprit could be the diverter valve, which is responsible for directing the water to the showerhead or the spout. If the diverter valve fails, it might not be able to redirect water from the tub spout to the showerhead fully. This results in water spilling from the tub spout even though the diverter is fully engaged.

You’ll need to buy a replacement diverter for the spout to remedy this problem. Avoid mixing brands, as many aren’t compatible. So, order a replacement part from the correct brand using the model number to select the right part.

How To Fix It

If you determine the diverter valve is the culprit behind the problem, you’ll need to access the assembly tucked inside the wall. While this project shouldn’t be an issue for avid DIYers, it is usually best left to a plumber if you’re unfamiliar with these projects.

Before you start tinkering with the tub spout, turn off the water supply to the area. In some cases, there might be a shut-off valve specifically designed for the bathroom (usually tucked away in a nearby closet). However, if you can’t find a shut-off valve, you’ll need to turn the water off to the entire home.

Once you turn off the water, you need to remove the tub spout by unscrewing it or removing the set screw. Once you remove the tub spout, you’ll see a sleeve covering the diverter, which you’ll need to remove. With the sleeve out of the way, you can remove the diverter with a socket wrench. Ensure you remove the seat washer with the diverter.

Replace the diverter, then retrace your steps to reinstall the assembly.

How Much Does It Cost To Have A Shower Diverter Valve Replaced?

Remember, you can always hire a professional to handle the task for you. In general, this type of project can cost anywhere from $225 to $575, although specific costs may vary based on several factors (location, labor costs, material costs, etc.).

In some cases, replacing the entire assembly might be necessary. This is common in older homes with equally ancient fixtures, so if your tub spout has seen a few decades of use, it might require replacing.

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