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Guide 01 · About four minutes

Check your thread before you order.
It takes ninety seconds.

Nearly every "doesn't fit" complaint in this category is preventable. The threads look almost identical in photos, they measure within a millimetre of each other, and by the time you find out you've already burned a return.

The short version

If you only read one paragraph

Commercial pre-rinse spray heads in the United States almost universally use 7/8”-20 UNEF — that's roughly 22.2 mm outside diameter with 20 threads per inch. Household faucets use 1/2” NPT (tapered) or European fixtures use G 1/2” BSPP. Those measure within about one millimetre of each other, which is exactly why people mistake them.

The important part: there is no home-faucet adapter. Nothing stocked anywhere turns a household faucet thread into a 7/8”-20 UNEF hookup. People have gone to hardware stores and searched industrial suppliers like McMaster-Carr and come back empty-handed. If your connection isn't already 7/8”-20 UNEF, a commercial spray head is not the solution, and no amount of PTFE tape will change that.
Already holding a caliper? Skip the reading and run the thread checker — one measurement, one verdict.
One exception within our own lineup: besides the standard 7/8”-20 UNEF head, the Achelous Brass Chrome model also offers an optional 3/4”-14 end thread for installations that run without the handle. If your hose end measures 3/4” with 14 threads per inch, check that model instead →
Adapter note, so nobody is surprised: the head-only models (CFPJ / CFPJ-01 / JFPJ-02) ship without adapters, exactly as packaged. The 38” and 45” head-plus-hose assemblies do include three adapters — 7/8” to 1/2” (garden hose), 7/8” to M22×1 (commercial faucet spout) and 7/8” to 3/4” (commercial faucet). None of the three adapts a home faucet, and the replacement hoses carry female 7/8”-20 UNEF on both ends.

The four connections you will actually meet

ThreadOutside dia.TPITapered?Where you find it
7/8”-20 UNEF ~22.2 mm20No — parallel The end of a commercial pre-rinse hose. The US standard.
3/4”-14 UNS ~19.1 mm14No The inlet into certain spray valve bodies themselves, including many B-0107 style units.
1/2” NPT ~21.2 mm14Yes Household faucets, many residential side sprayers.
G 1/2” BSPP ~21.0 mm14No European and some imported fixtures.

Nominal dimensions. Always confirm against your own part.

Note the trap in row two. A lot of confusion comes from mixing up two different positions on the same assembly: the thread that goes into the valve body, and the thread on the end of the hose. They are different sizes and desperate measurements get mixed up constantly. A replacement spray head only cares about the hose end.
Spec diagram of a real pre-rinse head labeled 7/8-20 UNEF male thread inlet
What a proper spec label looks like. If a listing cannot show you this, ask.

How to tell them apart with a $15 caliper

You do not need to be a plumber. You need a digital caliper and about ninety seconds.

  1. Close the supply stop under the sink, then unscrew the old spray head from the hose by hand. If it's seized, use a strap wrench — don't use pliers on the chrome.
  2. Measure the outside diameter across the male threads. Anything from about 20.8 to 22.4 mm falls in the ambiguous zone, so diameter alone will not give you the answer.
  3. Count threads per inch. Lay the caliper across exactly one inch of thread and count the peaks. Or count across a quarter inch and multiply by four — usually easier.
    Five peaks per quarter inch → ~20 TPI → almost certainly 7/8”-20 UNEF. Three to four peaks per quarter inch → ~14 TPI → it is a pipe thread, not your part.
  4. Check for taper. Measure the diameter at the tip and again near the base. If it gets measurably wider toward the base, that is a tapered pipe thread (NPT) and it will never properly seal in a straight UNEF fitting.
7/8”-20 UNEF 22.2 mm / 20 TPI / parallel this is the one you want 3/4”-14 UNS 19.1 mm / 14 TPI / parallel different position in the assembly 1/2” NPT 21.2 mm / 14 TPI / tapered narrows toward the tip
Diameter alone will not separate these. Pitch and taper will.

The two answers you can get

~22.2 mm, fine pitch, parallel → you're clear

That's a standard commercial pre-rinse hose end. Any direct-fit head of this type threads on by hand and gets snugged a quarter turn with a wrench. No adapter, no plumber.

~21 mm, coarse pitch, or tapered → stop

You have a household or European fixture. Ordering a commercial head will cost you the part, the shipping both ways, and about two weeks. There is no adapter that solves this.

Common mistakes worth avoiding

Still not sure?

Take a clear, well-lit photo of the hose end with something for scale — a coin or a ruler — and ask before you buy. Any seller who sells in this category should be able to look at that photo and tell you yes or no. If the answer comes back as "probably fits" or "should work", treat that as no.

Watch for this specific response: "Without more specifics on what fittings are referenced, I can't definitely confirm compatibility." A buyer in this category publicly gave a seller one star for exactly that non-answer — the review wasn't about the product, it was about being unable to get a straight reply. Vagueness here is expensive for everyone.
Check current price and full specs

Or first read what to try before you buy anything at all.

Common questions

Questions people ask before ordering

Is 7/8”-20 UNEF the same as 1/2” NPT?

No. They are close enough in diameter to look alike and different enough never to seal. UNEF is a parallel thread at 20 threads per inch; NPT is tapered at 14 threads per inch. If your fitting gets noticeably narrower toward the end, it is NPT and this head is not the part you need.

Can I just use an adapter to fit a household faucet?

Not reliably. People do go looking for one - hardware chains generally do not stock it, because the two threads use different sealing principles. A parallel thread seals on a washer; a tapered thread seals on the taper. An adapter between them is a leak waiting for pressure. Measure first instead.

How do I tell UNEF from BSPP?

Count thread peaks across one quarter of an inch. Five peaks means 20 TPI, which is UNEF. Three or four means 14 TPI, which puts you in pipe-thread territory - BSPP if parallel, NPT if tapered. When the count is unclear, a caliper across the male thread helps: about 22.2 mm points to UNEF.

My spray head screws onto a hose that has a handle. Does that change anything?

Yes, and in your favour. With the handle fitted, the connection is 7/8”-20 UNEF. Remove the handle and the valve body presents 3/4”-14 UNS instead. Both are covered by this head, so you have two ways to make it fit.

What if I still cannot tell what I have?

Do not guess. Send the brand and a photo through the fit-question form, or use the thread checker and pick the option that matches what you can measure. A wrong order costs you a return and a second wait.