What Adapter For
Your answer

Is my tub spout slip-on or threaded?

A small set screw under the spout, in a slot or hole right where it meets the wall, means a slip-on spout, held on 1/2" copper pipe by that screw. With no screw, it’s a threaded spout that screws onto 1/2" pipe thread, and you turn the whole spout to take it off.

Look under the spout, where it meets the wall. What’s there?

Use a flashlight. The screw sits in a small slot or hole on the underside.

A small screwTakes a hex (Allen) keyNo screwJust a smooth spoutThe spout is already offCheck what sticks out of the wall

What sticks out of the wall?

Smooth copper pipeNo threads on the endA short brass fitting with an O-ringFixed on the end of the pipeA pipe with threads on the endThreads with no O-ring, or copper with a threaded fitting
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Your tub spout

Slip-on spout, for 1/2" copper

A slip-on (slip-fit) spout slides over 1/2" copper pipe, held by the set screw underneath. Loosen that screw, then twist and pull the spout off.

On the package: Slip-on or slip-fit, 1/2 in. copper

Available on Amazon

Slip-on tub spout for 1/2" copper Hex key set
  • The copper must stick out of the wall by the length the new spout’s instructions give. It differs from one model to the next.
  • Smooth any burrs off the pipe end so it can’t cut the O-ring inside the spout, and snug the set screw without overtightening.

See also

Shower head thread size
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Your tub spout

Threaded spout, for 1/2" pipe thread

It screws onto a pipe nipple with 1/2" male pipe thread. To take it off, turn the whole spout counterclockwise, with a strap wrench if it’s tight.

On the package: 1/2 in. IPS, also sold as 1/2 in. NPT

Available on Amazon

Threaded tub spout, 1/2" IPS PTFE thread seal tape
  • Unscrew it first. If you find a brass adapter with an O-ring instead of a plain threaded pipe, you need a spout made for that adapter. A standard IPS spout won’t fit it.
  • The thread can sit deep inside a spout, so a new one may need a longer or shorter nipple. Check its instructions.
  • Wrap the nipple’s threads with thread seal tape before the spout goes on.

See also

Shower head thread size
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Your tub spout

A tub spout adapter

Many Delta spouts screw onto an adapter like this. The adapter is threaded, soldered or clamped with a set screw onto the pipe, and an O-ring on it seals inside the spout.

  • A replacement has to be a spout made for that adapter. Delta’s tub spout instructions list which spouts go with each of its adapters.
  • Screw the spout on by hand until it’s firm against the wall.

See also

Shower head thread size
Start over

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Slip-on and threaded compared

Slip-on and threaded tub spouts
Slip-on (slip-fit)Threaded (IPS)
Under the spoutA set screw in a slot or holeNo screw
Goes on1/2" copper tube, 5/8" acrossA 1/2" pipe nipple, 0.840" across the threads
Seals withUsually an O-ring inside the spoutThread tape or sealant on the nipple
To removeLoosen the screw, twist and pullTurn the whole spout counterclockwise, with a strap wrench if needed

Some spouts are sold both ways under different part numbers. Moen’s 3830 is the threaded (IPS) version of a 7" spout and the 3831 is the slip-fit one, which Moen labels CC. When choosing a replacement, look for the words slip-on, slip-fit or IPS on the box or the listing.

Delta’s adapter spouts

Many Delta spouts don’t fit the pipe directly. They screw onto a short brass adapter, and the adapter is fixed to the pipe in one of three ways: threaded onto a 1/2" NPT nipple, soldered to copper, or slid onto copper and held with its own set screw. Because that set screw is hidden inside the spout, a Delta spout with no screw underneath can still be sitting on copper. Unscrew it and look: a brass fitting with an O-ring on the pipe end is the adapter, and the new spout has to be one made for it.

How far the pipe sticks out

Each spout needs the pipe to stick out of the finished wall by a set amount, and the amount changes from model to model, even within one brand. Find the length in the new spout’s instructions before cutting anything.

Pipe length past the finished wall, from the makers’ instructions
SpoutTypePipe out from the wall
Kohler K-15135 to K-15138Slip-fit1-1/2" to 2-7/8"
Kohler K-15135 to K-15138Threaded, standard length4" (1/2" NPT nipple)
Kohler K-15135 to K-15138, 8" spoutThreaded7-1/8"
Moen, slip fit (tub/shower trim kit)Slip-fit1-1/2" to 3"
Moen, IPS (tub/shower trim kit)ThreadedElbow to wall, plus spout base to its thread, plus 1/4"
Delta RP48718, RP41591, RP64721, RP81273Slip-on1-3/8" to 2-1/2"
Delta RP36497Slip-on2-3/4" to 4-1/4"
Delta, threaded with no adapterThreaded1/4" to 4-3/16", by model

Switching from one type to the other

The pipe from the valve down to the spout should be 1/2" copper or threaded iron pipe. A slip-on spout needs copper. Don’t use PEX for that drop.

Putting the new spout on

  1. Shut off the main water supply.
  2. Take the old spout off the way its type comes off.
  3. Slip-on: cut the copper to the length the new spout calls for, then smooth the end with emery paper so no burr can nick the O-ring. Slide the spout on, push it against the wall and tighten the set screw firmly, without overtightening.
  4. Threaded: fit a nipple of the length the instructions give, wrap its threads with thread seal tape, and screw the spout on until it sits flush against the wall. Tighten it the way the spout’s instructions say: Kohler’s are snugged with a clean strap wrench, Delta’s are hand tightened firmly against the wall.
  5. Seal around the spout’s base where the instructions say to, with plumber’s putty or caulk, so water can’t leak behind the wall. Then run the tub and check for leaks.

Working on the shower head too?

Shower head thread size

Common questions

What size hex key fits a tub spout set screw?

Moen and Kohler call for a 5/32 inch hex key on their slip-on spouts. Delta's instructions list a 1/8 inch one.

What does IPS mean on a tub spout?

It marks the threaded version: the spout has a 1/2 inch pipe thread inside and screws onto a threaded pipe nipple. Kohler and Delta call the same nipple 1/2 inch NPT.

Keep going

Shower head thread sizeWhat pipe do I have?Pipe thread sizeP-trap sizeIdentify it

Where we get our information from

The sizes on this page come from published standards and the makers’ own documents. Checked against published data from Moen, Delta, National Bureau of Standards, Copper Development Association and Kohler.

See all 8 sources
  • National Bureau of Standards, Handbook H28 (1957) Part II: Table VII.2 (American Standard taper pipe threads, NPT) and Tables X.1–X.3 (hose coupling threads, NH)
  • Copper Development Association, Copper Tube Handbook (ASTM B88 tube dimensions)
  • Moen, Tub Spout Gate Assembly instructions (INS708): slip fit spouts have a set screw underneath, IPS spouts don't
  • Moen, one-handle tub/shower valve trim installation instructions (INS2153E): IPS spouts on 1/2" male pipe thread, slip fit on 1/2" copper only, pipe lengths
  • Moen, 3830 and 3831 7" diverter tub spout specification sheet: IPS or slip fit-CC connection, by part number
  • Kohler, Bath Spouts installation guide (K-15135 to K-15138, 1011610-2-D): 1/2" NPT nipple, slip-fit copper tube length, setscrew
  • Delta, Tub Spout Installation (107700 Rev. M): threaded, slip-on and adapter spouts, pipe lengths by model, no PEX drop
  • Delta, RP48718 tub spout product page: slips onto 1/2" copper water tube

General guidance from manufacturer and standards data. Parts vary by brand, so check the size printed on the package against what you measured. For gas lines or anything inside a wall, use a licensed plumber.