Showerhead Arm Threads vs. Toilet Rough-In & Flange
Comparing 2 standards across 14 specifications. 14 key differences identified.
Residential shower arms and flexible handheld hoses utilize standardized 1/2-inch pipe interfaces governed by ASME A112.18.1. The fixed wall supply arm uses a 1/2"-14 NPT tapered male thread that seals into an in-wall drop-ear elbow, while the exposed showerhead outlet features a 1/2"-14 NPSM straight thread sealing via a compressed rubber washer.
Toilet rough-in dimensions under ASME A112.19.2 define the exact centerline distance from the finished rear wall to the closet bolts on the floor flange. While 12.0 inches (305 mm) is the universal modern standard, 10-inch and 14-inch rough-in toilets accommodate legacy plumbing and thick tile remodels, sealing to a 4"×3" closet flange via a wax ring or rubber gasket.
Specification Comparison Table
14 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standard
|
ASME A112.18.1 / CSA B125.1 / NSF 61 | — |
|
Wall Inlet Thread
|
1/2"-14 NPT (Male Tapered Pipe Thread, 60° flank) | — |
|
Showerhead Outlet Thread
|
1/2"-14 NPSM (Male Straight Mechanical Pipe, 60° flank) | — |
|
Handheld Hose Female Swivel
|
1/2"-14 NPSM / ISO 228 G 1/2" conical swivel nut | — |
|
Maximum Showerhead Flow Rate
|
1.8–2.0 GPM (6.8–7.6 L/min) @ 80 PSI (EPA WaterSense) | — |
|
Wall Sealing Method
|
3–5 wraps of PTFE thread tape on 1/2" NPT wall nipple | — |
|
Showerhead Sealing Method
|
EPDM mesh filter screen / flat rubber washer in swivel nut | — |
|
Governing Standards
|
— | ASME A112.19.2 / CSA B45.1 / ANSI A112.19.5 |
|
Standard Rough-In Distance
|
— | 12.0 inches (305 mm) from finished wall to center of flange |
|
Alternative Rough-Ins
|
— | 10.0 inches (254 mm) compact | 14.0 inches (356 mm) legacy |
|
Closet Flange Size
|
— | 4" × 3" (fits inside 4" DWV pipe or over 3" DWV pipe) |
|
Closet Bolt Spacing & Size
|
— | 6.0 inches (152 mm) apart | 5/16"-18 or 1/4"-20 brass bolts |
|
Finished Floor Flange Height
|
— | Flange bottom must rest flush on top of finished flooring (1/4" proud) |
|
Sanitary Water Closet Seal
|
— | 100% pure petroleum wax gasket with poly horn or silicone elastomer |