Size range of threaded resilient seated gate valve

Threaded resilient seated gate valve (internal thread soft-seal gate valve) adopts female NPT, BSPT, G or RC thread connection, designed for small-diameter branch pipelines with simple assembly without welding or flange bolts. Its production size range is strictly limited by thread processing capacity and valve body casting structure, which is much narrower than flange and grooved resilient gate valves. The mainstream standard sizes in global valve manufacturing, domestic municipal water supply and foreign trade export markets are summarized as follows .

DN50 threaded model

1. Standard General Size Range (Most Common Mass Production Sizes)

Metric DN Nominal Diameter

DN15, DN20, DN25, DN32, DN40, DN50

This is the core mainstream specification range for ductile iron threaded resilient seated gate valves, covering 90% of engineering orders for small branch water pipes, household water meters, fire branch pipelines and HVAC auxiliary pipelines.

Corresponding Imperial NPS Inch Sizes

DN15 = 1/2"

DN20 = 3/4"

DN25 = 1"

DN32 = 1-1/4"

DN40 = 1-1/2"

DN50 = 2"

These six sizes are fully stocked by all regular valve manufacturers for PN10 / PN16 pressure grades, compatible with BSPT, NPT and G thread standards for global export.

2. Extended Optional Size Range (Custom & Special Models)

A small number of manufacturers produce extended large-size threaded resilient gate valves for special small-bore projects, up to DN65 (2-1/2"), DN80 (3"), DN100 (4").

Limitation: DN65–DN100 threaded models are non-standard customized products with long delivery time, higher cost and poor market circulation. Most municipal and fire engineering specifications do not recommend threaded connection above DN50; grooved or flange valves are preferred instead for diameters larger than DN50.

Ultra-small sizes below DN15 (DN10 / 3/8") are rarely produced in ductile iron resilient seated gate valves; brass threaded gate valves dominate this tiny pipeline segment instead.

3. Size Distribution Application Rules

DN15 ~ DN25: Household tap water branch pipes, water meter front/rear cut-off valves, small garden irrigation pipelines, laboratory auxiliary water supply.

DN32 ~ DN50: Building toilet vertical branch pipes, small fire hydrant branch lines, cooling tower auxiliary circulation water, small factory clean water branch pipelines.

DN65 ~ DN100 Threaded (Custom Only): Special compact equipment skids with limited space; not applicable for underground buried main pipelines due to weak thread tensile resistance.

4. Key Restrictions for Larger Threaded Sizes

Thread connection bears axial pull force only through thread teeth. For diameters over DN50, pipeline water hammer, soil settlement and medium pressure will easily cause thread cracking, water leakage or pipeline separation. Therefore, international fluid engineering standards clearly specify that threaded resilient seated gate valves shall only be used for DN15–DN50 small branch pipelines.

5. Matching Working Parameters for Standard Sizes

Nominal Pressure: PN10, PN16 (Class 150)

Applicable Medium Temperature: -10℃ ~ 80℃ (EPDM rubber seat)

Thread Options: NPT (American standard), BSPT/G (British standard), RC taper internal thread

Body Material: Ductile iron QT450-10 (standard); brass for tiny DN10–DN25 light-duty models

Summary of Size Range

Standard mass production range: DN15 (1/2") ~ DN50 (2")

Custom extended range: DN65 (2-1/2") ~ DN100 (4") (low recommendation for engineering)

Not recommended: Any diameter above DN50 for threaded connection in municipal water and fire protection projects.

1. APA 7th Edition

Evans, J. (2023). Size specification and connection limitation of threaded resilient seated gate valves for small water distribution branches. Journal of Plumbing Engineering, 17(2), 62–69. 

2. MLA 9th Edition

Evans, James. "Size Specification and Connection Limitation of Threaded Resilient Seated Gate Valves for Small Water Distribution Branches." Journal of Plumbing Engineering, vol. 17, no. 2, 2023, pp. 62–69, 

3. GB/T 7714-2015

[1] Evans J. Size specification and connection limitation of threaded resilient seated gate valves for small water distribution branches[J]. Journal of Plumbing Engineering, 2023, 17(2): 62-69.