Garden Hose Thread (GHT) Size Guide: Dimensions & NPT Adapters

Garden hose thread (GHT) is one of the most common threaded connections in the world — found on every outdoor spigot, washing machine supply port, and industrial washdown station. Yet it confuses buyers every day because it looks similar to NPT pipe thread but is fundamentally different. At Apex Flow Solutions, we stock brass GHT fittings and GHT-to-NPT adapters so you can bridge the gap cleanly without leaks or cross-threading headaches. This guide covers GHT dimensions, how GHT compares to NPT, how to choose the right adapter, and answers the questions our customers ask most.

What Is Garden Hose Thread (GHT)?

Garden Hose Thread — formally designated NH (National Hose) thread per ASME B1.20.7 — is a straight (non-tapered) thread standard developed specifically for garden and industrial hose couplings. There is effectively only one nominal size: 3/4 in. – 11.5 NH. Every standard garden hose, every standard outdoor spigot, and every standard washdown nozzle uses this single size, which is why the term "garden hose thread" can refer to the thread without specifying a diameter.

You will also see two abbreviations used interchangeably with GHT:

  • MHT (Male Hose Thread) — the external (male) threaded end; found on spigots, nozzles, and the male end of adapters.
  • FHT (Female Hose Thread) — the internal (female) threaded end; found on hose couplings, supply-line connectors, and the female end of adapters.

GHT, NH, MHT, and FHT all describe the same 3/4–11.5 thread form. The prefix simply tells you whether the fitting is male or female.

GHT Dimensions & Thread Specifications

Because there is only one GHT size, the specification table is straightforward:

Parameter Value Notes
Standard designation 3/4 in. – 11.5 NH Per ASME B1.20.7
Thread form Straight (parallel) Not tapered like NPT
Threads per inch (TPI) 11.5 Unique to GHT — not shared with any NPT size
Major (outside) diameter — male 1.0625 in. (1-1/16 in.) Measured at thread crests
Minor (root) diameter — male ~0.9597 in. Approximate
Thread angle 60° Same angle as NPT/UNF
Sealing method Hose washer (gasket) Compression seal at face; NOT thread-seal
Equivalent ISO designation 3/4 in. GHT IEC/DIN markets may use "W 26.44 × 1/11.5" notation

The 11.5 TPI pitch is unique to GHT — no NPT or UN thread shares it — which is one reason GHT and NPT are not interchangeable even though the thread angle and approximate diameter look superficially similar.

GHT vs. NPT: Key Differences

This is the question that generates the most field confusion. The short answer: GHT and NPT will NOT thread together reliably and should never be forced. Here is why:

Property GHT (3/4 – 11.5 NH) 3/4 in. NPT 1/2 in. NPT
Thread form Straight (parallel) Tapered (1 in./ft taper) Tapered (1 in./ft taper)
Threads per inch 11.5 14 14
Major OD 1.0625 in. 1.0500 in. 0.8440 in.
Sealing method Rubber washer / gasket Thread engagement + sealant Thread engagement + sealant
Teflon tape required? No — washer seals Yes Yes
Interchangeable with GHT? — No No

Because the OD of 3/4 NPT (1.050 in.) is close to GHT (1.0625 in.), a male NPT fitting will partially engage a female GHT coupling and vice versa — but the threads will cross immediately, causing galling and a guaranteed leak or fitting damage. Always use a proper GHT-to-NPT adapter when connecting these two thread types.

Selecting a GHT-to-NPT Adapter

The right adapter depends on the gender of each connection point and the NPT pipe size you are connecting to. The most common combinations are:

Adapter Type GHT End NPT End Typical Use Case
MHT × 3/4 FNPT Male GHT Female 3/4 NPT Connecting a hose to a 3/4 in. pipe valve or manifold
FHT × 3/4 MNPT Female GHT Male 3/4 NPT Attaching a hose coupling to a 3/4 in. threaded pipe nipple
MHT × 1/2 FNPT Male GHT Female 1/2 NPT Smaller pipe systems, utility sinks, drain ports
FHT × 1/2 MNPT Female GHT Male 1/2 NPT Equipment drain connections with 1/2 in. NPT ports
Double FHT coupler Female GHT × Female GHT — Joining two male hose ends
Double MHT coupler Male GHT × Male GHT — Joining two female hose ends / extending a line

All Apex Flow brass GHT adapters include a pre-installed rubber washer on the GHT female end. Brass is the preferred material for industrial and commercial use: it resists dezincification better than low-grade alloys and withstands the chlorine and mineral content of municipal water supplies.

Browse our full Garden Hose Fittings collection to see current MHT, FHT, and adapter inventory.

Washer & Seal Maintenance

GHT connections seal differently than NPT connections, and treating them incorrectly is the leading cause of leaks on hose connections:

GHT ends — use a washer, not tape

  • GHT is a face-seal connection. The rubber (or EPDM) hose washer sitting inside the female coupling is what creates the seal, not thread engagement.
  • Do NOT apply Teflon tape or pipe dope to GHT threads. Tape on a straight thread cannot create a seal and will merely build up on the threads, making the connection difficult to tighten.
  • Inspect washers regularly. A cracked, flattened, or missing washer is the cause of almost every GHT drip. Replacement washers are inexpensive — keep a handful on hand.
  • Hand-tighten GHT couplings, then snug with pliers (one-quarter turn). Over-tightening deforms the washer and accelerates leaks.

NPT ends — sealant is required

  • On the NPT side of any GHT-to-NPT adapter, the taper-thread engagement is the primary seal, and a thread sealant is mandatory.
  • Teflon (PTFE) tape is the most common choice for water service. Pipe dope (anaerobic or PTFE paste) is preferred for higher-pressure or gas service.
  • See our guide: Teflon Tape vs. Pipe Dope — When to Use Each.

Common Applications

GHT and GHT-to-NPT adapters appear across a wide range of industrial, commercial, and residential uses:

  • Industrial washdown stations — GHT hose bibs connect to 3/4 or 1/2 NPT plumbing lines via adapters; stainless or brass washdown guns thread directly onto MHT spigots.
  • Irrigation and agriculture — Drip emitter lines, sprinkler heads, and soaker-hose manifolds use FHT inlets; quick-connect adapters speed up field changes.
  • Water transfer pumps — Many portable centrifugal and diaphragm pumps include GHT suction and discharge ports; GHT-to-NPT adapters let you mate them to pipe or cam-lock systems.
  • Equipment drain connections — Boilers, water heaters, air compressor moisture traps, and cooling towers often have 1/2 or 3/4 NPT drain ports; an FHT × MNPT adapter lets you run a standard garden hose to the floor drain during seasonal blowdown.
  • Pressure washers and chemical injectors — Most pressure washer supply lines are GHT; adapters to 3/8 or 1/2 NPT connect chemical supply tanks and chemical injector manifolds.
  • RV and marine fresh-water fill ports — Shore-water inlets on RVs and dock water supply stations use MHT spigots so standard garden hoses connect without tools.

Standards & References

  • ASME B1.20.7 — Hose Coupling Screw Threads (Inch) — the governing standard for GHT/NH thread dimensions and tolerances in the United States.
  • ASME B1.20.1 — Pipe Threads, General Purpose (Inch) — the governing standard for NPT dimensions; useful for comparison when specifying adapters.
  • NFPA 1963 — Fire hose coupling threads (NST/NH) — note that fire-service NH threads share the NH designation but have different dimensions from garden-hose NH; verify application before ordering.

Frequently Asked Questions

What size is garden hose thread?

All standard garden hose thread is one size: 3/4 in. – 11.5 NH (National Hose), as defined by ASME B1.20.7. The major (outside) diameter of the male thread is approximately 1-1/16 in. (1.0625 in.) and the thread pitch is 11.5 threads per inch. This single size covers virtually every residential, commercial, and light-industrial hose connection in North America.

Is garden hose thread the same as NPT?

No — GHT and NPT are not interchangeable. GHT is a straight thread that seals with a rubber washer; NPT is a tapered thread that seals via thread engagement and sealant. The thread pitch also differs: GHT uses 11.5 TPI while 3/4 NPT uses 14 TPI. Forcing them together will cross the threads and damage both fittings. Use a GHT-to-NPT adapter to connect the two systems.

Do garden hose fittings need Teflon tape?

Not on the GHT (hose thread) side. GHT connections seal with a rubber face washer inside the female coupling — tape on a straight thread does nothing to improve the seal. However, if your GHT fitting also has an NPT end (as on a GHT-to-NPT adapter), you must apply Teflon tape or pipe dope to the NPT male threads before installation. Always check which thread type is at each end of the fitting.

What does MHT and FHT mean?

MHT stands for Male Hose Thread and FHT stands for Female Hose Thread — both refer to the same 3/4–11.5 NH (GHT) thread form. MHT describes an external (male) threaded connection, such as a spigot or a nozzle. FHT describes an internal (female) threaded connection, such as a hose end coupling. The letters simply indicate gender, not a different thread standard.

Can I connect a garden hose to a 1/2 in. pipe?

Yes, with the right adapter. A FHT × 1/2 MNPT adapter screws into a 1/2 in. NPT female pipe fitting (apply sealant to the NPT male threads), and the female GHT end accepts a standard male garden hose coupler. Going the other direction, a MHT × 1/2 FNPT adapter threads onto a 1/2 in. NPT male pipe nipple and presents a male GHT spigot for hose connection. Both configurations are common for draining equipment, connecting portable pumps, and supplying washdown stations from 1/2 in. branch lines.

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