Underground Gate Valve with A Stem Cap for Waterworks

At Metalsin, we supply ductile iron NRS gate valves with a stem cap for waterworks. These valves installed in underground pipelines primarily carrying water intended for human consumption are required to be fitted with a stem cap to enable them to be operated by a ring-key and bar or T-shaped key. These key-operated stem cap gate valves may be designed and manufactured in accordance with a series of international standards including AWWA C515, BS 5163, ISO 7259, EN 1171, DIN 3352, and SANS 664.

Design Features

1. Buried Underground: Underground gate valves are buried to protect them from harsh weather, vandalism, and external interference while maintaining consistent water pressure and system efficiency. Their placement out of sight improves urban aesthetics and conserves space, and locating them within a protected underground network simplifies maintenance and operational control, ensuring long-term reliability and efficient water distribution.

Ductile iron non-rising stem gate valves fitted with a stem cap, made to BS 5163 DN150 PN16, for water supply pipelines.

2. Stem Cap for Key Operation: The gate valve fitted with a stem cap is opened or closed by turning a small cap mounted to the top of the valve stem, converting the stem configuration to mate with an operating T-key or ring key & bar — instead of using a traditional large handwheel. This stem cap not only rotates the valve stem to raise or lower the internal gate (or wedge), thereby controlling the fluid flow, but it also protects the stem and provides a compact, space-saving interface for manual operation; in many non-rising stem designs, where the stem does not visibly move, an attached indicator to the cap helps infer the valve’s position. These valves are commonly used in water distribution, fire protection, and HVAC systems, especially in underground installations such as pipelines or manholes, where the non-protruding design minimizes the risk of damage during installation and maintenance in confined spaces.

Various stem caps & a typical T-shaped key for the operation of ductile iron underground gate valves for waterworks.

3. Epoxy Coating: Both interior & exterior surfaces of underground buried gate valves in water systems shall be coated with robust, corrosion-resistant epoxy treatments (FBE or liquid epoxy) that comply with ANSI/AWWA C550 standards and NSF/ANSI 61 certification to ensure non-toxicity and water quality. For waterworks designed to European standards, the epoxy coating shall also comply with EN 1074-1 & EN 1074-2. Typically, a minimum coating thickness of about 6 mils — often increased to 8~16 mils for more demanding conditions — is applied after proper surface preparation such as near-white grit blasting, ensuring strong adhesion and durability. Quality control tests, including holiday detection and adhesion/impact assessments per ASTM standards, are performed to verify the integrity of the coating, thereby protecting the valves from harsh soil environments, extending their service life, and ensuring reliable long-term performance in underground installations.

Drawings, Materials & Dimensions

Typical drawings of the stem cap (A), ring key & bar (B), and T-key (C) for ductile iron underground gate valves.

The stem cap shall be firmly attached to the valve stem, and if necessary, be secured by a hex nut in a manner that they can be removed when required. Generally, they can be made from a series of ductile irons including EN-GJS-450-10 (EN-JS1040), EN-GJS-500-7 (EN-JS1050), GGG 40, GGG 50, BS 2789 Grade 450/10, 500/7.