Quick Answer:
If water still leaks from the tub spout after you replaced the diverter, the most common causes are a mismatched part or a missing/faulty seal (O-ring or washer). First shut off the water, confirm the replacement diverter is the correct type for that spout or valve, and inspect for missing seals. If parts don’t match or sealing surfaces are damaged, call a plumber.
Why This Happens
There are a few simple reasons a new diverter keeps leaking:
- The replacement diverter doesn’t match the original spout or valve type. Diverters come in different lengths, diameters and mounting styles (slip-on, screw-on, internal cartridge types).
- A required O-ring or washer was missing, damaged, or not seated properly when the new diverter was installed.
- Debris, mineral buildup, or corrosion on the spout seat or diverter body prevents a full seal.
- The spout or valve body itself is worn or cracked, so a replacement diverter can’t make a watertight seal.
If the leak only appears after the shower has run a long time, check pressure and seal condition and consider the note about constant flow in the linked guide: Leak only when shower on long.
Step-by-Step What to Do
1. Turn off the water and test
- Shut off the shower or the whole-house supply if you can’t isolate the line. Open the tub spout briefly to relieve pressure.
- Run the shower briefly to confirm where the leak is coming from (spout, behind wall, or valve area).
2. Remove the spout and inspect parts
- Carefully take the tub spout off (or remove the diverter trim) to see the diverter assembly and seating surface.
- Look for missing or damaged O-rings, rubber washers, or split rings. These are small and easy to miss.
3. Confirm the replacement diverter matches the spout/valve model
- Compare the new diverter to the original: check length, diameter, and the way it attaches (slip-on, screw-in, or cartridge). Part numbers or model markings help if available.
- If the new part sits too shallow, too deep, or wiggles in the seat, it’s probably the wrong model and won’t seal.
4. Verify seals and reinstall correctly
- Replace any worn O-rings or washers. Even if the new diverter came with seals, the old ones might have left residue—clean the mating surfaces first.
- Lightly lubricate rubber O-rings with a plumber’s silicone grease (not petroleum jelly) so they seat without tearing.
- Reinstall the spout/diverter per the manufacturer’s instructions. Hand-tighten and test before finishing up; avoid over-tightening.
5. Test for leaks and observe
- Turn water back on and run both the tub and shower diverter several times. Watch for drips immediately and after a few minutes of flow.
- If a leak persists, remove the diverter and re-check seating surfaces for corrosion or irregularities that prevent sealing.
What Not to Do
- Don’t assume any diverter fits any spout—compatibility matters.
- Don’t continue using mismatched parts; if parts don’t match, a plumber is appropriate.
- Don’t force or hammer parts into place—you can damage the spout or valve seat.
- Don’t ignore small drips; they usually get worse and can hide damage behind the wall.
When to Call a Professional
- If you’ve confirmed the diverter matches the spout and you replaced seals but the leak continues.
- If the spout or valve seat is corroded, cracked, or badly worn so a new diverter can’t seal against it.
- If the leak appears to come from behind the wall, or you can’t access the diverter without cutting into finished surfaces.
- If the job requires removing tile, opening the wall, or replacing internal valve components you’re not comfortable handling.
If the leak started during or after nearby work, there can be hidden issues from changes in piping—see this related note: Leak started after remodel.
Safety Notes
- Shut off water supply before disassembling any plumbing. If you can’t isolate the shower, shut the main off.
- Protect the tub and fixtures with a towel to avoid scratches while working.
- Use the right tools: pipe wrenches and pliers can damage fittings if misused. Use padded jaws when possible.
- Don’t use heat or open flame near plumbing. Avoid chemical drain products near seals you’re reinstalling.
Common Homeowner Questions
- Why is it still leaking after I installed a new diverter?
Often the replacement is the wrong style or an O-ring/washer is missing or damaged. - Can I reuse the old O-ring?
It’s usually better to replace O-rings; they compress and age, and new ones ensure a proper seal. - How long should this fix take?
If parts match and seals are replaced, expect 30–60 minutes; mismatched parts or internal valve issues take longer or need a pro.
For more related articles, see the Tub Spout Leaks When Shower Is On hub.