Shower Diverter Not Working? 5 Causes (Water Comes Out of Tub Spout)

You turn on the shower, pull up the diverter on the tub spout, and instead of full flow through the showerhead, water still pours from the tub spout. The diverter won't stay up, feels loose, or only redirects part of the flow. You end up with water coming from both the showerhead and the tub, and wasted water running straight down the drain.

A failing shower diverter is a common bathroom issue and one of the most irritating because it wastes water every time you shower. A diverter that doesn't fully redirect the flow can waste 15-30 gallons per shower, adding $100-$200 to your water bill each year.

The good news: most diverter failures have simple, predictable causes and relatively inexpensive fixes. After decades of diagnosing these issues across, we've found that the same handful of problems keep recurring. Below is a breakdown of the five most common reasons diverters fail, ranked by how often we encounter them, plus quick diagnostic checks, DIY repair options with cost ranges, and when it's time to call your pros at Dalmatian Plumbing.

What Is a Shower Diverter? (Understanding the Mechanism)

What a shower diverter does: A shower diverter is the valve that redirects water from the tub spout to the showerhead. When you pull a knob, press a button, or turn a handle, the diverter blocks the tub spout outlet and forces water up the shower pipe instead.

Main diverter types:

1. Tub spout diverters (most common):
   Built into the tub spout with a pull-up knob or gate. Pulling the knob lifts an internal mechanism that blocks the spout opening and redirects water to the shower. Common in single-handle and two-handle tub/shower setups.

2. Three-valve wall-mount diverters:
   A separate middle handle on the wall that diverts water from the tub to the shower. Found in older homes and higher-end fixtures.

Why diverters fail: Diverters are mechanical components that are constantly subjected to pressure, temperature fluctuations, and mineral buildup. The internal gate, seals, or valve surfaces wear out, corrode, or collect deposits. When they can't fully block the tub spout or can't stay engaged, water keeps leaking out of the spout during a shower.

Core symptom: Water continues to flow from the tub spout while the shower is on. This wastes water, reduces showerhead pressure, and signals that the diverter needs repair or replacement.

The 5 Causes of Shower Diverter Failure (Ranked by Frequency)

Based on three decades of repairing shower diverters in surrounding communities, here are the five causes ranked from most to least common. Starting with #1 gives you the highest probability of quickly identifying your problem.

Cause #1: Worn Diverter Gate or Seal (Tub Spout Type) - 60% of Cases

Tub spout diverters with pull-up knobs have an internal gate that blocks water from exiting the spout. The gate is usually made of rubber or plastic, and over time, it becomes brittle, warped, or coated with mineral deposits. Once the gate can't seal tightly, water continues to flow from the tub spout even when the diverter is engaged.

Why is this the top cause: Local water is moderately hard (60-120 mg/L). Over 5-10 years, mineral buildup accumulates on the gate and seal, preventing a watertight closure or locking the mechanism in place.

How to diagnose a worn tub spout diverter:

• Pull the diverter knob while water is running. If the knob won't stay up, the internal spring or lock has failed.

• If water continues flowing from the spout with the knob raised, the gate isn't sealing.

• If water flow is reduced but not stopped, the gate is partially closed, with gaps.

• Visible mineral buildup, rust, or corrosion inside the spout suggests the seal has been compromised.

DIY fix: Most tub spout diverters aren't designed for internal repairs. Replacing the entire spout is the practical solution.

Most tub spouts either screw off counterclockwise or release via a set screw underneath. Bring the old spout to the hardware store to match attachment style and pipe size (usually 1/2" or 3/4").

Pro tip: Measure the distance from the wall to the center of the tub spout opening. If the pipe sticks out too far or too little, you'll need a spout designed for that projection or one with an adjustable connection (common ranges: 1/2" to 4").

Cause #2: Mineral Buildup Inside Diverter Mechanism - 20% of Cases

Even if the diverter gate isn't worn out, mineral deposits from moderately hard water can keep it from moving or sealing correctly. Calcium, magnesium, and iron accumulate over time, creating a white or orange/brown crust that binds the moving parts.

How to diagnose mineral buildup:

• White crust or orange/brown staining is visible inside the tub spout

• The diverter knob feels stiff or requires extra force

• Diverter works inconsistently, sometimes seals, sometimes doesn't

• Grinding or scraping sounds when pulling the knob

DIY fix: You can sometimes restore the diverter by deep-cleaning it instead of replacing the spout.

Vinegar soak (best early-stage option):

1. Remove the tub spout (use the same removal steps as Cause #1).

2. Submerge it in white vinegar (5% acidity) for 2-4 hours.

3. Scrub with a toothbrush to remove loosened deposits.

4. Rinse thoroughly and reinstall.

5. If the spout can't be removed or the buildup is heavy, replacing the spout is more reliable.

Prevention tip: Some homes have water hardness above 100 mg/L. A whole-house water softener reduces mineral deposits across all plumbing fixtures and extends the lifespan of shower components, water heaters, and dishwashers.

Cause #3: Broken or Corroded Diverter Stem (Wall-Mount Type) - 12% of Cases

In three-valve setups with a separate diverter handle, the internal stem that operates the diverter valve can corrode, strip, or break. When that happens, the handle can no longer engage the valve, so water keeps flowing from the tub spout.

How to diagnose a broken diverter stem:

• The diverter handle turns, but nothing changes; water keeps coming from the tub spout

• The handle feels loose, wobbly, or "slips" when turning

• The handle spins endlessly without a stop point

• Water leaks behind the wall around the diverter escutcheon (valve body corrosion)

• You hear water running inside the wall when the diverter is engaged

DIY fix: Repair requires replacing the stem or cartridge inside the wall.

Replacement steps:

1. Shut off the water to the bathroom.

2. Remove the diverter handle (usually a screw hidden under a cap or behind the lever).

3. Remove the escutcheon plate.

4. Pull or unscrew the old cartridge/stem (corroded ones may require pliers or a cartridge puller).

5. Install the new cartridge with the included washers and O-rings.

6. Reassemble all trim and test.

Common complication: If you don't know the valve brand or the cartridge has been discontinued, finding the correct replacement becomes the biggest challenge. This is where a pro is worth it: experienced plumbers can identify valves by trim style and have access to suppliers that carry hard-to-find or obsolete cartridges.

Cause #4: Incorrect Pipe Length (New Installation or DIY Error) - 5% of Cases

Tub spout diverters require a very specific pipe length protruding from the wall, usually 2.5 to 3.5 inches, depending on the spout design. If the pipe is too long or too short, the diverter gate inside the spout can't align with the pipe opening, so it can't seal properly. The spout will still run, but the diverter will never block the flow.

Why this happens: During DIY installations or renovations, people often choose a spout solely based on pipe diameter, ignoring pipe projection. The spout fits the threads just fine, but the water outlet doesn't line up with the diverter gate internally. Even "universal" spouts can fail if the pipe projection is wrong.

How to diagnose incorrect pipe length:

• The issue began immediately after installing a new tub spout

• Spout doesn't sit flush against the wall (pipe too short)

• Spout is pressed tightly against the wall (pipe too long)

• When you pull the diverter, strong water still exits the spout, not just a small bypass trickle

• The replacement spout was a "universal fit" model instead of one matched to your setup

Solution and costs:

If the pipe is too long, a plumber must cut it inside the wall to the correct length.

If the pipe is too short, you'll need a spout designed for short pipe projections, or the pipe must be extended.

This repair usually requires a plumber unless you're comfortable cutting and extending copper or PEX inside the wall and have the right tools.

Cause #5: Failed Pressure Balance Valve (Behind the Wall) - 3% of Cases

Modern single-handle tub/shower systems use a pressure-balancing valve or a thermostatic mixing valve behind the wall to regulate temperature and pressure. When the diverter portion of this valve fails, it can't fully shift water from tub mode to shower mode, even if the tub spout diverter is brand-new.

How to diagnose pressure balance valve failure:

• You have a single-handle tub/shower setup (not separate hot/cold handles)

• Engaging the diverter causes wild temperature swings

• You hear banging or hammering inside the wall when switching to shower mode

• The issue continues even after replacing the tub spout

• Water drips from the tub spout or showerhead even when the valve is "off," indicating internal valve leakage

Professional repair: Fixing this requires opening the wall to access the valve body; there's no front-side repair.

This is a professional-only job. Pressure balance valves are safety devices that prevent scalding, and incorrect installation can cause dangerous temperature spikes or violate plumbing code.

The Hidden Cost of a Failing Shower Diverter

Many homeowners ignore a weak diverter for years, letting some water run from the tub spout during showers. The waste adds up fast.

• Water waste: If 20% of the flow leaks from the tub spout, you lose about 4 gallons during a 10-minute shower. Family of four, one shower each per day = 5,840 gallons wasted per year.
• Cost impact: Atlanta's water + sewer rate averages about $0.005 per gallon. 5,840 gallons = ~$30/year wasted on water alone. Delay the repair 5-10 years and you've thrown away $150-$300, far more than the cost of a new spout ($15-$40).
• Energy waste: If the leaking water is hot, you're also wasting the energy used to heat it. That adds another $20-$40 per year to a typical household's budget.
• Pressure impact: Reducing the flow by 20% at the tub spout reduces shower pressure by the same amount. Lower pressure leads to longer showers, which wastes even more water and energy.

The bottom line a DIY fix or a professional repair pays for itself quickly, usually within 2-3 years, and immediately restores full shower pressure and proper function.

Expert Shower Diverter Repair Throughout Metro Atlanta

At Dalmatian Plumbing, we've spent more than 30 years diagnosing and repairing shower diverter issues across Atlanta, Marietta, Roswell, Alpharetta, Sandy Springs, and nearby areas. Because we've seen every type of diverter failure, our plumbers can usually identify the cause within minutes and give you an upfront, accurate estimate before any work begins.

We know homeowners want straight answers, whether a repair is simple enough to handle on your own or whether professional service is the smarter move. That's why we offer clear diagnostic service calls, and we pinpoint the exact problem, explain your options, and provide fixed pricing for any repairs.

A functioning diverter saves water, improves shower pressure, and pays for itself quickly. Call Dalmatian Plumbing or schedule service online. We'll diagnose the issue, explain your options clearly, and get your shower working properly.