Brass Pipe Fittings for Pressure Washers

Half the leaks we diagnose at the counter come down to the wrong two dollar fitting, not a bad pump or gun. Brass pipe fittings handle the plumbing on nearly every cold and hot water machine because brass threads clean, seals tight, and shrugs off plain water for decades. Bring your old fitting to the store or call 301-519-9274 and we will match threads on the spot.

How to Read Brass Fitting Sizes Without Guessing

Pipe thread sizing trips up almost everyone once. The sizes are nominal, which means a 1/4" NPT male fitting actually measures about 0.54" across the threads. If you measure the outside diameter with a ruler and shop by that number, you will buy one size too big every time. Go by the marked size on the old fitting, count threads per inch if you have to, or just bring it in. MPT means male pipe thread, the threads are on the outside. FPT means female pipe thread, threads inside. Both are tapered NPT threads, and the taper is what seals: the flanks wedge tighter as you turn until metal binds against metal.

That taper also sets the rule for tightening. Run the fitting hand tight, then wrench it 1.5 to 3 more turns for sizes up to 1". You want roughly four to six threads engaged. Past that you are not sealing anything, you are splitting the female fitting or galling the threads. If it still weeps after three turns, back it out, clean the threads, and reseal. More muscle is never the fix.

Know Your Shapes: Adapter, Bushing, Plug, Barb

The names matter when you order over the phone. An adapter has a female thread on one end and a male on the other, and it changes size or gender in a straight line. A bushing is male outside and female inside, made to step a big port down to a smaller thread while staying almost flush. An Allen head plug closes an unused port, sitting recessed so it will not snag, which is why pump makers use them on spare inlet and gauge ports. A hose barb converts pipe thread to a push-on hose connection, clamped with a band. Elbows and street elbows turn corners, and a locknut backs a bulkhead or panel mount. Every one of those does a slightly different job, and swapping one for another is how leaks start.

Common Jobs and the Brass Fitting That Does Them

These are counter staples, but quantities swing with the season. Call first if you need a handful today.

Brass, Steel, or Stainless

Brass is the default for water plumbing on pressure washers, hot or cold. It will not rust, it machines to clean threads, and it costs a fraction of stainless. Move to stainless steel fittings when the line carries strong chemicals, softwash mix, or lives near salt air, because brass slowly loses zinc in that service and turns pink and brittle. Plated steel fittings earn their keep on high pressure discharge plumbing where strength matters most. One caution on mixing: brass threaded into steel is normal and fine on a washer frame, but keep sealant on every joint so corrosion never gets a dry start.

From the Field

Watch what leaves this shelf and you learn how rigs actually fail. Allen head plugs sell constantly, mostly to people who removed a gauge or injector and need to close the port before the next job. Bushings outsell straight adapters because pumps keep coming with bigger ports than the plumbing people already own. And the heavy-wall adapters go to the contractors who cracked a standard fitting at the unloader from vibration. If a joint on your machine shakes, buy the heavy version the first time. The other thing we see weekly is tape shreds inside injectors and unloaders. Two wraps of tape, started one thread back from the end, is plenty. Wrap the whole nose and the excess ends up in your check valves.

Related Collections

• All fittings if you are not sure what family you need
• 90 degree elbows and street elbows
• Hex bushings and hex couplers
• Close nipples and nipple fittings
• Allen head plugs and caps
• Tees and adapters
• Hose barbs and quick connects
• Thread locker and sealants
• Prefer to match threads in person? Visit the Gaithersburg store

Frequently Asked Questions

What do MPT and FPT mean on brass fittings?

MPT is male pipe thread, cut on the outside of the fitting. FPT is female pipe thread, cut inside. Both are tapered NPT threads, so they tighten and seal as the taper wedges together.

Why does my 1/4" fitting measure more than 1/4" across?

Pipe thread sizes are nominal, based on old pipe bore standards, not actual measurements. A 1/4" NPT male runs about 0.54" across the threads. Match the marked size or bring the fitting in rather than trusting a ruler.

How tight should a brass pipe fitting be?

Hand tight plus 1.5 to 3 full turns with a wrench for sizes up to 1", which lands about four to six threads engaged. If it leaks past that, the fix is cleaning and resealing the threads, not more torque.

Should I use thread tape or paste on brass fittings?

Either seals a tapered joint. Use two wraps of tape started one thread back from the end, or a thin coat of paste. Skip the heavy wrap jobs, since shredded tape ends up in injectors and unloader valves.

Are brass fittings OK for hot water pressure washers?

Yes. Brass handles burner outlet temperatures without complaint and is standard on hot water machine plumbing. Just confirm the fitting's pressure rating covers your machine's max PSI.

When should I use stainless instead of brass?

Any line that carries bleach mix, strong degreasers, or lives in coastal air. Chemicals leach zinc out of brass over time and leave it brittle. For plain water, brass lasts for years at a lower cost.

Can you match an odd fitting I cannot identify?

That is a daily event here. Bring it to the counter or text a photo with a coin for scale to 301-519-9274 and we will identify the thread and hand you the mate.