Galvanized Bushings

A galvanized hex bushing steps a threaded connection down from a larger size to a smaller one. Its outside male threads screw into the larger fitting and its inside female threads take the smaller pipe, so one short fitting does the reduction. The zinc coating fights rust, which is why you’ll find these on water and air lines and on outdoor piping that sees weather. For a gas line, use the fittings your gas code and inspector call for; the zinc doesn’t make a fitting right for gas.

How to read a bushing size

Bushings are named male size first, female size second. A 1 x 3/4 bushing has 1-inch male threads on the outside and 3/4-inch female threads on the inside. So the first number matches the fitting you’re screwing into, and the second matches the pipe you’re bringing to it.

Both numbers are nominal pipe sizes. Pipe is named by nominal size, so “3/4-inch” is the trade name for that pipe, not a measurement you’ll get by putting a tape across the threads. The easy way to get it right is to bring the old fitting, or the end of the pipe, to the counter and match it there.

A bushing reduces; a nipple extends. If you need more length between two fittings, you want a nipple, not a bushing.

WBC’s galvanized hex bushings

These are the reductions WBC carries:

Male thread (into the larger fitting)	Female thread (takes the smaller pipe)
1/4 inch	1/8 inch
3/8 inch	1/4 inch
1/2 inch	1/4 inch
1/2 inch	3/8 inch
3/4 inch	1/4 inch
3/4 inch	3/8 inch
3/4 inch	1/2 inch
1 inch	1/2 inch
1 inch	3/4 inch
2 inches	1-1/2 inches

The 1 x 3/4 drops a 1-inch fitting to a 3/4-inch line; the 3/4 x 1/2 does the same job one size down.

The hex body is there for a reason. It gives your wrench a flat surface to bite on, so you can tighten the bushing into the larger fitting without chewing it up.

Get the threads right: NPT

Galvanized bushings for American pipe are threaded NPT, the American tapered pipe thread with a 60-degree thread angle. British fittings use BSPT, a 55-degree tapered thread, and G threads are straight, unsealed threads. They can look alike, and they don’t seal to each other. When you’re tying into an existing line, the thing to check is that the fitting you’re screwing into is NPT too. If it came off a piece of imported equipment, don’t assume.

Seal it and tighten it right

Wrap the male threads with PTFE plumber’s tape or brush on pipe dope. Screw the bushing in by hand until it’s snug, then finish it with a wrench on the hex. Hold the fitting it’s going into with a second wrench so you don’t twist the whole line while you tighten.

Galvanized, malleable iron and the zinc

“Galvanized” tells you about the coating, not what the fitting is made of. The body can be malleable iron or steel; the zinc is the surface treatment. Hot-dip galvanizing leaves a thicker, firmly bonded zinc layer; electro-galvanizing leaves a thinner, even one.

Either way, the zinc wears away over time. On an old galvanized water line, look hard at the fitting you’re threading into. If it’s rusted at the threads, a new bushing won’t save it. Montana’s winter is interior renovation season, and opening up an old line during a remodel is the time to find that out, not in the middle of a frozen-pipe repair.

The Pick

Buy the 1-inch male by 3/4-inch female galvanized hex bushing to step a 1-inch fitting down to a 3/4-inch pipe. For the other reductions, pick the bushing whose first number matches the fitting and whose second matches the pipe. Make sure both sides are NPT, tape or dope the threads, and tighten with a backup wrench.

Frequently Asked Questions

What is a galvanized bushing used for?

A galvanized bushing screws into a larger threaded fitting and takes a smaller pipe, so it steps the connection down a size. You’ll see them on water and air lines; for gas, follow your gas code. The zinc coating resists rust, which makes them a sound choice where the piping sees weather.

How do you read galvanized bushing sizes?

The male size comes first and the female size second, so a 1 x 3/4 bushing has 1-inch outside threads and 3/4-inch inside threads. These are nominal pipe sizes, the names of the pipes, not measured thread diameters. Match the first number to your fitting and the second to your pipe.

Do galvanized bushings need thread sealant?

Yes. Use PTFE plumber’s tape or pipe dope on the male threads, hand-tighten, then finish with a wrench while a second wrench holds the fitting steady. That keeps the joint tight without twisting the rest of the line.