One side runs G thread, the other runs NPT — this adapter connects them. It takes a 1" G (BSPP) female parallel thread and joins it to a 1¼" NPT male tapered thread, so you can tie two different plumbing standards together without touching existing pipework.
Lead-free brass construction, rated for potable water. A washer ships in the box — G thread seals against a flat face, not with tape, and everything you need is already included.
Thread Connections
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Female side: 1" G (BSPP) — parallel thread
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Male side: 1¼" NPT — tapered thread
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Seal method: Washer on G side (included); tape optional on NPT side
Where It Gets Used
- Larger-diameter supply lines where G and NPT standards meet
- Shower systems connecting imported BSPP fixtures to US NPT pipework
- Hose-to-fixture hookups requiring a thread step-up
- Commercial and residential fixture retrofits — anywhere a 1" G outlet needs to connect to 1¼" NPT
Features
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Lead-free brass — safe for drinking water and potable water systems
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Washer included — proper seal on the G thread side, right out of the box
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Steps up thread size — 1" G female to the larger 1¼" NPT male in one fitting
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Screw-in install — no special tools, standard wrench only
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1¾" hex — fits a standard 45mm wrench for final tightening
Specifications
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SKU: CSSL56160960
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Material: Lead-Free Brass
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Finish: Brass
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Female Thread: 1" G (BSPP) — parallel
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Male Thread: 1¼" NPT — tapered
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Overall Length: 1⅜" (38mm)
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Male Thread Diameter: 1¼" (Ø34mm)
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Male Thread Length: ⅝" (18mm)
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Hex Size (Female End): 1¾" (45mm)
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Installation Method: Screw-In
Package Includes
- 1 × Adapter — 1" G Female to 1¼" NPT Male
- 1 × Washer
How to Install
- Check both sides — female connection must be 1" G (BSPP), male side must accept 1¼" NPT. Measure first.
- Place the included washer on the G thread (female) side before threading. This creates the seal.
- Hand-tighten first to avoid cross-threading, then snug with a 1¾" (45mm) wrench. Don't overtighten.
- Plumber's tape on the NPT male side is optional but won't cause any issues.
- Run water for a minute and inspect the joint before closing up the installation.
FAQ
Q) What's the difference between G (BSPP) and NPT thread?
G thread is parallel — diameter stays constant the full length. NPT tapers slightly and seals by compression. They don't connect directly, which is what this adapter is for.
Q) Do I need plumber's tape?
Not on the G thread side — the washer handles that seal. Tape is optional on the 1¼" NPT male side.
Q) Is this safe for drinking water?
Yes. Lead-free brass, rated for potable water use.
Q) What wrench fits this?
1¾" (45mm) across the flats on the female hex end.
Q) Is this the same as the 3/4" NPT version?
No — the male end here is 1¼" NPT, which is larger. If you need 3/4" NPT male, that's a different adapter. Check your fitting size before ordering.
Q) Will this work with my shower system?
If your shower has a 1" G female outlet and connects to a 1¼" NPT male supply line, this is the right fit. Confirm both thread sizes before purchasing.
