Garden hose thread and pipe thread don’t mix, even at the same “3/4 inch” size, so joining them takes a brass adapter with hose thread on one end and pipe thread on the other. Hose thread is about 1-1/16" across with 11.5 threads per inch, and 3/4" pipe thread is 1.05" across with 14.
The end that screws onto a faucet, with threads inside and a rubber washer
Male pipe thread (MIP), 1.05" across
What fits
3/4" MHT x 3/4" FIP adapter
On the package: 3/4 in. MHT x 3/4 in. FIP
male hose thread x female pipe thread, brass
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Reading adapter names
Adapters are named by their two ends. F means female (threads inside), M means male (threads outside). HT is hose thread; IP (also written PT or NPT) is pipe thread.
Not sure of the pipe size? Measure across the male pipe threads: about 0.84" is 1/2", about 1.05" is 3/4". Brass adapters are sold under exactly these names, e.g. “3/4 in. FHT x 1/2 in. MIP”.
Why they don’t fit
They differ in three ways:
- Thread count. Garden hose thread has 11.5 threads per inch. 1/2" and 3/4" pipe thread have 14. Threads with different spacing don’t mesh.
- Shape. Pipe thread (NPT) is tapered: it narrows slightly toward the end of the pipe, and the seal is made by the threads wedging together with tape or sealant. Hose thread keeps one diameter and doesn’t seal on the threads at all.
- Seal. A hose joint seals on the rubber washer inside the female end. Garden hose thread doesn’t work with any other thread system.
3/4" hose thread (1.0625") and 3/4" pipe thread (1.050") are only 1/80" apart across the threads. You can’t tell them apart with a tape. Count the threads over one inch instead: 11½ is hose, 14 is pipe.
Where you’ll find each thread
- Garden hose thread: the spout of an outdoor faucet (Woodford’s wall faucets have a “3/4" male hose thread nozzle”), both ends of a garden hose, washing machine valves and hoses (BrassCraft’s washer hoses are 3/4" female hose thread at both ends), and the parts at the start of a drip system.
- Pipe thread: the back of an outdoor faucet where it joins the house pipe (Woodford and Watts sell 1/2" and 3/4" pipe-thread inlets), galvanized and brass pipe fittings, and the threaded ends of valves.
- Same pitch, different size: 1" pipe thread also has 11.5 threads per inch, but it’s 1.315" across, much too big for a hose.
Sealing an adapter
- Pipe-thread end: wrap Teflon thread tape (PTFE tape) around the threads, or use pipe thread sealant (pipe dope). Tapered pipe threads “always need a sealant”.
- Which threads get the tape: the male ones (threads outside), whether that’s the pipe or the adapter. Use tape only on male pipe threads, wrapped the way the threads spiral. For standard threads, that’s clockwise as you look at the end. Start at the first thread and don’t let the tape hang over the end.
- Hose-thread end: no tape. Make sure the female end has a good rubber washer and tighten it by hand. The same goes for hose-thread drip parts: no Teflon tape on the threads.