Quick Answer:
If a newly installed tub spout leaks during showers the most likely causes are a mismatched connection type (threaded vs slip-on), the spout not seating properly against the wall, or a missing adapter or seal. Start by checking whether the spout matches the pipe stub and that the spout sits fully against the wall rather than bottoming out on the pipe. These checks often reveal a simple fit or alignment issue you can fix without replacing plumbing behind the wall.
Why This Happens
- Two common spout inlet types exist: a threaded female inlet that screws onto a male threaded pipe, and a slip-on inlet that slides over a smooth pipe stub and is held by a set screw or O-ring. If you install the wrong type, water can spray or run behind the spout.
- If the spout is installed but doesn’t seat fully against the wall — for example because it’s hitting the pipe stub too early — the interior path won’t line up and water can escape around the base.
- Missing adapters, worn O-rings, or a loose set screw on slip-on spouts can let pressurized shower water leak out during use.
Step-by-Step What to Do
Step 1 — Observe and isolate when the leak happens
- Run the shower and note whether the leak occurs only with the shower on or also when the tub valve is used. This helps pinpoint whether the spout or a diverter is involved.
- Turn off the shower when you plan to work on the spout. You don’t usually need to shut off the whole house water to inspect a tub spout, but use caution if you must remove the spout.
Step 2 — Remove the spout for inspection
- Identify how the spout is attached. For slip-on spouts, there will usually be a small set screw on the underside; loosen that and pull straight off. For threaded spouts, rotate counterclockwise to unscrew from the pipe stub.
- Inspect the pipe stub: is it threaded or smooth? Is there a short metal adapter or a rough end that would prevent the spout from seating flush?
Step 3 — Verify threaded vs slip-on connection matches the pipe stub
- Confirm the spout inlet type matches the pipe stub. A slip-on spout won’t seal on a threaded stub without an adapter; a threaded spout won’t screw on a smooth stub.
- If the wrong style was purchased, getting the correct spout or the proper adapter usually resolves the leak.
Step 4 — Check seating and for bottoming out
- Before reinstalling, look inside the spout inlet for any obstructions or missing parts (O-rings, sleeves, or diverter seals).
- Slide or screw the spout back on gently and watch how it meets the wall. Confirm the spout seats fully against the tile or escutcheon and isn’t stopping early because it’s bottoming out on the pipe stub. If it bottoms out, the inlet won’t align and water can leak.
Step 5 — Reinstall correctly and test
- For threaded connections, wrap a few turns of plumber’s (PTFE) tape on the male threads and screw the spout on until it seats snugly — not overly tight.
- For slip-on spouts, ensure the O-ring or rubber sleeve is present and the set screw is tightened to hold the spout in place without deforming it. Aim for a flush fit against the wall, then run the shower and observe for leaks.
What Not to Do
- Don’t overtighten a new spout to fix leaks—misalignment can worsen it and damage threads or fittings.
- Don’t assume extra force or shims will solve a mismatched inlet type; the wrong spout style needs the correct adapter or a replacement spout.
- If fitment is unclear, a plumber is appropriate. Trying to force parts on without the right adapter can lead to more expensive repairs.
When to Call a Professional
- If you find that the pipe stub behind the spout is damaged, corroded, or cut too short, that often requires a plumber to repair or install the correct adapter.
- Call a pro if you’ve confirmed the inlet type matches, the spout seats fully, and you still have leaks — particularly if the leak gets worse after you worked on it: Leak worsened after plumbing repair.
- If the leak is limited to one water temperature or seems related to the valve rather than the spout, get help — for example if only hot water causes dripping: Tub spout leaks only on hot water.
Safety Notes
- Work carefully around tile and fixtures to avoid chipping or cutting yourself. Wear gloves and eye protection when removing corroded parts.
- Do not use excessive force when removing or installing spouts; snapping a brittle spout or stripping threads can create a larger leak or require wall access.
- If you must access plumbing behind the wall, turn off the water supply and consider hiring a professional to avoid water damage.
Common Homeowner Questions
- Why does the spout drip only when the shower is on? A misaligned inlet or loose fitting can let pressurized shower water escape at the spout base; check seating and the inlet type.
- Can I fix a leaking spout myself? Often yes — if it’s a simple mismatch, missing O-ring, or loose set screw. Replace the spout with the correct type or add an adapter if needed.
- How can I tell if the spout is bottoming out? Remove the spout and slide it on without tightening; if it stops short of the wall or rocks, the pipe stub is likely contacting the inside before the spout can seat.
For more related articles, see the Tub Spout Leaks When Shower Is On hub.