If your fixture ends in a 1" G (BSPP) female thread and the pipe you're connecting it to runs 1 1/2" NPT male, this is the piece that bridges the two without cutting into your existing plumbing. It's cast from lead-free brass and comes with a washer already sized for the G thread side.
Thread Types
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Female end: 1" G (BSPP), parallel thread
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Male end: 1 1/2" NPT, tapered thread
Why This Combination
A 1 1/2" NPT male end is larger than the standard 3/4" or 1 1/4" sizes in this range, so it's typically used where higher flow matters — main supply runs, larger shower valve bodies, or commercial-grade fixtures feeding into a G-threaded component.
What's In The Box
- 1 adapter (1" G female × 1 1/2" NPT male)
- 1 sealing washer
Technical Details
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SKU: CSSL56160970
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Material: Lead-Free Brass
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Finish: Brass
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Installation: Screw-In
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Overall Length: 1 1/2" (38.5mm)
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Male Thread Diameter: 1 1/2" (Ø38.5mm)
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Male Thread Length: 5/8" (18.5mm)
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Hex Size: 1 7/8" (50mm)
Fitting It Together
- Check both ends against your existing pipework before threading anything in — 1" G female on one side, 1 1/2" NPT male on the other.
- Set the washer into the G thread side first. That's where the seal actually happens, not on the NPT side.
- Thread by hand, then bring it up snug with a wrench sized to the hex.
- Tape or sealant on the NPT threads is optional, not required for the seal.
- Turn the water on and check the joint before you call it done.
Common Questions
Q) Why does the G side need a washer but the NPT side doesn't?
G (BSPP) threads run parallel and can't seal on their own, so they rely on a washer. NPT threads taper and bite down as they're tightened, which creates the seal on that end.
Q) Is 1 1/2" NPT bigger than the 1 1/4" version you sell?
Yes — this is the larger of the two. Double-check the size stamped or labeled on your existing fitting before ordering, since they're not interchangeable.
Q) Can I use this on a main water line, not just a fixture?
It's suited to that — the larger NPT end is generally chosen for higher-flow or supply-line applications rather than a single small fixture.
Q) Does the brass contain lead?
No, it's lead-free brass, suitable for potable water.
Q) What size wrench do I need?
The hex measures 1 7/8" (50mm) across the flats.
Q) What if my thread is G 1" but slightly different from BSPP?
G thread and BSPP refer to the same British Standard Pipe Parallel standard, so if your fitting is marked G1" or 1" BSPP, it should match.
