Thread Standards

Thread Cross Reference

Thread Standards
When attaching two threaded devices together, there are a number of factors that come into play, the critical ones are size, thread standard and gender. Material composition is also a factor -- aluminum, brass, copper, plastic, iron, galvanized, etc. In fire fighting, coupling devices are mainly aluminum or brass. Plastic is not common but can be used selectively. Galvanized and iron should be avoided due to the rusting factor. Typically, copper is not used in firefighting systems.
When talking threads, you will encounter numerous types or systems. Generally speaking, NPSH is used in Canada for the smaller hoses (1" & 1½") with NST (NH) used in USA. Forestry applications typically use NPSH or quarter turn quick connect fittings. The charts below will outline characteristics of various thread standards.

THREAD	SYSTEM NAME	SEAL METHOD	THREAD COMPATIBILITY
NPT	American Standard Taper Pipe Thread (National Pipe Tapered)	Thread Seal or Washer Seal*	Male NPT - Female NPT, NPTF, NPSM, NPSH Female NPT - Male NPT, NPTF
NPSH	American Standard Straight Pipe for Hose Couplings (National Pipe Straight Hose)	Washer Seal	Male NPSH - Female NPSH, NPSM Female NPSH - Male NPSH, NPT, NPTF, NPSM
NH or NST	American Standard Fire Hose Coupling Thread (National Hose Thread also known as National Standard Thread)	Washer Seal	Male NH (NST)- Female NH(NST) Female NH (NST)- Male NH (NST) Not compatible with other systems. Thread pitch and diameters of fire threads may vary according to local and municipal regulations.
GHT	Garden Hose Thread	Washer Seal	Male GHT - Female GHT Female GHT - Male GHT Not compatable with other systems.
NPTF	American Standard Taper Pipe Fuel Dry Seal Thread (National Pipe Tapered)	Thread Seal or Washer Seal*	Male NPTF - Female NPTF, NPT, NPSM, NPSH Female NPTF - Male NPTF, NPT
IPS	Iron Pipe Straight Thread	Washer Seal	Generic Name for Straight Pipe Thread (NPSH)
IPT	Iron Pipe Thread		Generic Name for All Pipe Thread More information is needed.
TIPT	Tapered Iron Pipe Thread	Thread Seal	Generic Name for Tapered Pipe Thread (NPT)
CHT	Chemical Hose Thread (also known as Booster Hose Thread). Same as 1" National Hose Thread (NH) or American Standard Fire Hose Thread (NST)	Washer Seal	1" Male NH (NST) with 1" Female NH (NST) 1" Female NH (NST) with 1" Male NH (NST) 1" Thread is used on both ¾" hose and 1" hose. Not compatible with other systems
BSPP	British Standard Pipe Parallel	Washer Seal	Male BSPP - Female BSPP Female BSPP - Male BSPP Female BSPP - Male BSPTr M-BSPP not compatible /w F-BSPTr
BSPTr	British Standard Pipe Tapered	Thread Seal or Washer Seal*	Male BSPTr - Female BSPTr, BSPP* Female BSPTr - Male BSPTr F-BSPTr not compatible /w M-BSPP
Numerous other thread standards may be encountered. In USA, larger cities or specific municipalities may use unique standards for municipal water and fire fighting services. Examples are New York City Fire Department Thread and Chicago Fire Department Thread. One reason for these unique threads may be to reduce occurrences of theft of hoses and accessories. Canada also has unique threads -- often by province. You may encounter CSA, BCT, QST, NFLD, NSST, WCT, etc. If you need to be compatible with your local fire department, you should determine what they use and what you would need to attach to their equipment.

COMMONLY USED THREADS

	National Standard Thread NH/NST		Straight Iron Pipe NPSH/IPT		Standard Pipe Thread NPT/TIPT		British Standard Pipe Thread BSP
Size	ODM	TPI	ODM	TPI	ODM	TPI	ODM	TPI
¾"	1.375	8	1.035	14	1.050	14
1"	1.375	8	1.295	11.5	1.315	11.5	1.309	11
1½"	1.990	9	1.878	11.5	1.900	11.5
2"	2.515	8	2.352	11.5	2.375	11.5	1.882	11
2½"	3.068	7.5	2.841	8	2.875	8
3"	3.623	6	3.470	8	3.500	8	2.960	11
3½"	4.243	6	3.970	8	4.000	8	4.125	3
4"	5.010	4	4.470	8	4.500	8	4.625	3
4½"	5.760	4	4.970	8	5.000	8	5.125	3
5"	6.260	4			5.563	8	5.625	3
6"	7.025	4			6.625	8	6.625	3

Note:
Residential garden hose fittings are ¾" GHT with 1.0625" ODM x 11½ TPI

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Thread Standards

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