To replace a tub spout, check underneath for a set screw. If there is one, loosen it and slide the slip-on spout off its copper pipe. If not, unscrew the threaded spout counterclockwise. Measure the pipe sticking out of the wall, buy a spout that matches the connection and length, then seal and install it.
Slip-on, threaded, or diverter: know which one you have
There are three things to identify, and the box you buy has to match all three.
| Feature | Slip-on (slip fit) | Threaded (IPS) |
|---|---|---|
| How to spot it | Set screw on the underside near the wall | No set screw; spout turns off as one piece |
| Pipe it needs | Smooth 1/2-inch copper tube | 1/2-inch pipe threads (a threaded nipple, or copper with a threaded adapter) |
| How it seals | O-ring inside the spout grips the copper | Threads, sealed with thread seal tape |
| Removal | Loosen the set screw, pull straight off | Turn counterclockwise |
| Common failure | Set screw overtightened, O-ring cut on a burr | Corroded nipple, cracked plastic spout body |
### Diverter or no diverter
The third thing is the diverter. A diverter spout has a knob on top (or a pull-down ring at the tip) that blocks the spout and sends water up to the showerhead. If you have a tub and shower on one valve and no separate diverter handle on the wall, you need a diverter spout. If the switching is done by a handle or knob on the wall trim, a plain non-diverter spout is fine. Delta's installation sheet notes that non-diverter tub spouts can be used with shower diverter systems.
If your diverter is the reason you're here, the spout is the repair. On most spouts the diverter is built into the body, so the whole spout gets replaced. Our guide to a shower diverter not working covers how to tell a spout diverter from a valve diverter.
### Copper stub-out or threaded nipple
Once the old spout is off, look at the pipe. Moen's instructions spell out the difference. A threaded spout connects to the valve with 1/2-inch pipe, or 1/2-inch copper tubing with a threaded adapter. A slip-fit spout connects with copper tubing only, and no threaded adapter is needed.
So a slip-on spout needs bare copper. It won't seal on a threaded nipple, and it won't seal on PEX or CPVC. A threaded spout needs threads, either a brass or galvanized nipple or copper with a male threaded adapter soldered on. If the pipe you find doesn't match the spout you want, universal adapters exist. Delta's RP92217 adapter, for example, is listed "for use with threaded 1/2" NPT Iron Pipe, 1/2" CWT Copper Sweat and Slip-On applications."
Measure the pipe before you buy
This is the step people skip, and it's why a new spout ends up sitting an inch off the wall or leaking at the O-ring. Measure from the finished wall surface (the face of the tile) to the end of the pipe.
### Slip-on spouts
Moen's one-handle tub and shower instructions say to "ensure 1/2" copper water tube is at least 1-1/2" min to 3" max for slip fit tub spout." Too short and the O-ring inside the spout never reaches the pipe. Too long and the spout can't sit flush against the tile. Other brands use different numbers, so check the instruction sheet for the spout you're buying. Delta's slip-on adapter sheet, for example, has you position its adapter to a dimension shown in the drawing.
The end of the copper matters as much as the length. Moen says the pipe end "must be free from burrs inside and out" and the outside "must be free from nicks and scratches." Delta says the end of the copper tube must be chamfered free of burrs to prevent O-ring damage. If you cut the pipe shorter, deburr and lightly bevel the outside edge before you slide the spout on.
### Threaded spouts
For threaded spouts, the length that matters is how far the threads reach into the spout. Moen gives a simple formula: measure from the inside elbow shoulder to the wall (y), and from the threaded adapter inside the spout to the base of the spout (x), then add 1/4 inch. In Moen's words, "(y) + (x) + 1/4” = Pipe Length." If your nipple is the wrong length, replace it with one that fits. Nipples come in fixed lengths, so bring the old one to the store.
### The pipe behind the wall
Spout manufacturers are also specific about the piping between the valve and the spout, because it affects whether the diverter works. Delta says the supply between valve and spout "must be a minimum of 1/2” (13 mm) copper or iron pipe in a straight drop 8” (203 mm) minimum and 18” (457 mm) maximum long with only one iron pipe or copper 90° elbow to the tub spout nipple," and adds: "Do not use PEX tubing for a tub spout drop." Moen's troubleshooting says its tub spout can be no less than six inches and no greater than eleven inches below the valve. You can't change that without opening the wall, but it explains some problems a new spout won't fix.
Step by step: replacing the spout
A spout is downstream of the valve, so as long as the shower is off, there's no pressure on it. You don't need to shut off the house water.
- 1Protect the tub. Lay a towel in the tub under the spout so a dropped screw or tool doesn't chip the finish or go down the drain.
- 2Remove a slip-on spout. Loosen the set screw underneath with a hex key (Moen's slip-fit spouts use a 5/32-inch hex). Back it out a few turns, then twist and pull the spout straight off. Old caulk may hold it; cut it with a utility knife.
- 3Or remove a threaded spout. Turn it counterclockwise. If it won't move by hand, wrap it in a rag and use a strap wrench or padded pliers. Go slow. If the nipple starts turning with the spout, stop, because you're unscrewing the pipe from the fitting inside the wall.
- 4Clean up. Scrape off old caulk and putty. On a threaded nipple, clean the threads with a wire brush and check for corrosion or cracks. On copper, check for nicks and deburr the end.
- 5Measure and buy. Use the numbers above. Bring the old spout with you.
- 6Install a threaded spout. Wrap the threads with thread seal tape, clockwise. Moen also calls for a sealant (plumber's putty or caulk) around the base of the pipe "to prevent leaking behind the wall." Screw the spout on by hand until it's snug and pointing straight down at the tub. Moen notes that some plastic (ABS) spouts can crack from certain pipe thread compounds, so read the sealant label or stick to tape.
- 7Or install a slip-on spout. Lubricate the O-ring if the instructions say to, slide the spout over the copper until the base meets the wall, and tighten the set screw. Moen says to tighten it until it "just starts to bind," then finish by hand. Delta warns not to overtighten, because you could puncture the tube and cause a leak.
- 8Seal and test. Seal where the spout meets the tile if the spout's instructions call for it; Delta's sheet for one threaded model, for example, says to add sealant to the groove in the back of the wall escutcheon as needed. Turn on the tub, then pull the diverter and check that the shower gets full flow.
Done. If water still pours from the spout while the shower runs, read the next section before buying another spout.
Is the leak the spout, the diverter, or the valve?
A new spout only fixes spout problems. Here's how to sort it out.
| Symptom | What it usually means |
|---|---|
| Spout drips with the shower and tub both off | Worn valve cartridge or washers, not the spout |
| Water pours from the spout while the shower runs | Worn spout diverter, or a piping problem behind the wall |
| A small trickle from the spout while showering | Can be normal on some valves |
| Water runs out behind the spout or along the wall | Failed O-ring or loose threads at the pipe, or missing caulk |
| Water comes out of the showerhead while you fill the tub | Restriction or piping problem, called "stacking" or "shower rise" |
A drip with everything off is the valve. The spout can't hold water back; it only directs what the valve lets through. Moen's own troubleshooting table lists a leak or drip from the spout with the fix "Replace cartridge." See our guide on how to replace a shower cartridge. If the drip is coming from inside the wall rather than the spout, read about a leaking shower valve behind the wall.
Some spout flow while showering can be normal. Kohler says its Rite-Temp valves don't have a positive shut-off diverter, and that "ANSI standards allow for .1 to .3 gallons per minute to flow from the spout when diverted to the showerhead." A light trickle is within that. A steady stream is a worn diverter.
Water from the head while filling the tub is a restriction, not a bad spout. Moen says this "is caused by either a restriction in the system or an installation issue." Its checklist includes debris inside the spout, PEX or CPVC used from the tub port, too many elbows, and a spout mounted too far from the valve. Pull the spout and check for debris first, since that one's free.
In Phoenix, hard-water scale is a common reason a spout diverter stops sealing. If the diverter is stiff or crusted, a new spout is usually quicker than trying to clean it.
When to call a plumber
Most spout swaps are fine as DIY. Call a licensed plumber if the threaded nipple twists or breaks inside the wall, if the copper stub-out is too short to reach the O-ring (it has to be extended with a soldered fitting), if the piping behind the wall is PEX or CPVC where the spout manufacturer requires copper or iron, or if water shows up inside the wall instead of at the spout. Those mean opening the wall or soldering, and a mistake there turns into water damage.
HQ Plumbing & Air is licensed and insured, gives upfront pricing and free estimates, and handles tub and shower repairs 24/7 if a leak can't wait.