What thread size is a handheld shower hose?

A handheld shower’s hose has a nut at each end. On American Standard, Delta and Moen wall elbows, the hose screws onto 1/2" NPSM, a straight thread. Kohler uses G1/2 instead, the same thread as 1/2" BSP. The elbow itself screws onto the pipe with 1/2" NPT. Match a new hose to the thread on your elbow and handset.

Threads by maker

NPSM is the American straight pipe thread for free-fitting joints on fixtures. Because it’s straight rather than tapered, it doesn’t seal on the threads: the washer, seal or O-ring in the joint does. Moen’s A720 side outlet is NPSL, another straight 1/2" pipe thread, the one meant for locknut joints.

Kohler’s G1/2

Kohler’s K-9514 hose, K-72594 handshower and K-976 and K-22175 elbows are threaded G1/2 on its US and Canadian sheets, the parallel thread also called 1/2" BSP. For the K-72594 handshower, Kohler lists its own K-8593 or K-9514 metal hoses, or its K-45981 or K-45982 ribbon hoses, as required parts.

1/2" NPSM and G1/2 are easy to confuse. Both have 14 threads per inch, and across the male thread they measure 0.818" and 0.825" (20.78 and 20.96 mm), less than a hundredth of an inch apart. The thread angle differs: 60° on NPSM, 55° on G1/2. When parts come from different makers, check that both spec sheets name the same thread.

Where the hose gets its water

• A wall elbow (Moen calls it a drop ell) screws onto a 1/2" NPT pipe nipple coming out of the finished wall and gives the hose a male outlet facing down.
• A shower arm diverter goes on the end of the shower arm. The fixed head screws onto one outlet and the hose onto another, and a control sends water to the head, the hand shower or both.

Delta’s diverters screw onto the arm with a female 1/2-14 NPSM thread. A male NPT thread like the arm’s fits into a female NPSM one, but the reverse doesn’t work: a male NPSM outlet isn’t compatible with a female NPT fitting.

Which end goes where

• Delta: one hose nut is conical, the other hex. On Delta’s In2ition hose, the hex nut goes on the shower head’s outlet (the supply end) and the other end on the hand shower, with a hose washer in each nut and every joint hand tight.
• Kohler: a screen washer goes into the handshower’s inlet and the hose collar threads onto it. The hose nut at the other end goes on the shower outlet, wrench tight but not overtightened.
• American Standard: a seal goes into each hose end. The hand shower end is hand tight; the wall supply end is tightened with an adjustable wrench, not overtightened.
• Moen: for its bracket-mounted handheld, the hose and its washers go on hand tight at the bracket and the handheld.

Kohler’s handshower guide and American Standard’s 8888 instructions put a wrench on the wall end, while Delta’s In2ition and Moen’s INS10819 instructions keep every hose joint hand tight. Follow the sheet that came with your parts.

Tape goes on the pipe threads only

Sealant or tape belongs on the tapered NPT joints. American Standard’s 8888.068 and .069 wall supplies go on a taped or sealed 1/2" NPT nipple, and Delta’s U4929 diverter goes on a taped shower arm. The hose joints seal on their washers. None of these sheets tapes them, and Moen’s bracket handheld goes on without thread seal tape.

How to tell which you have

1. Look for the brand and model on the handset, the wall elbow or the diverter, or find the box or manual.
2. Look the model up on the maker’s spec sheet, which prints the thread on its drawing.
3. With no model to go on, choose a hose from the same maker as the elbow or diverter it hangs from.

Turn off the water before you take off a shower head or open a hose joint, and check each end of the hose for leaks when it’s back on. Plumbing codes may require a vacuum breaker or backflow preventer in line with a handheld shower; check your local code.