Pipe to hose · 2 pack
POWERTEC 70125-P2 pipe-to-hose adapter, 2 pack
The one fitting on this shelf that publishes all four of its diameters — which is the whole of what a nominal size hides.
Every figure below names its source. Each one is a manufacturer
specification read off the listing itself. The judgments are ours.
Four diameters, on one part
Narrow end: 4 in outside, 3-49/64 in inside.
Large end: 4-7/32 in outside, 3-31/32 in inside.
The two ends do opposite jobs. The narrow one is a male spigot that goes inside a
four-inch-internal hose; the large one is a female socket that goes over a
four-inch-external port.
So one part turns a hose into a port and a port into a hose — which is the
conversion a branched duct needs at every machine.
No other fitting on either half of this shelf publishes more than one diameter.
Why nominal is not a measurement
A four-inch fitting is not four inches anywhere on it.
The POWERTEC listings on this shelf publish the actual figures: a four-inch
nominal end measures 3-31/32 in across the outside and 3-39/64 in across the
inside — 100.8 mm (3.97 in) and 91.7 mm (3.61 in). The difference between those two is the wall, and
the difference between one maker’s outside and another’s inside is the leak.
That is what the shelf’s own intro means by the adaptors that never quite fit.
Nominal sizing is a naming convention; the join is decided by the sixty-fourths.
And this part proves it
Within one four-inch-nominal fitting: 3-49/64, 3-31/32, 4, and 4-7/32 inches.
A fitting from another maker whose outside measures 4-1/16 will not enter this
one’s socket, and nothing on either label would have said so.
Two of them
Which is the right quantity, because a ducted shop needs one at each end of
every flexible drop.
The published Y-piece on this shelf comes with three hose clamps. This comes
with none, and the listing says non-threaded — so the joint is a friction fit and
a worm-drive clamp is the missing part.
On a four-inch duct a loose joint is not a leak. It is an open inlet, and the
system draws from the room instead of the machine.
Availability
Read on the day this page was built: $18 at the American Amazon shop.
Read from Keepa on the day this page was last revised; stock and price both move without notice.
Prices quoted in this text were read on 2026-10-07. The live price is at the top of the page.
