Gate valves for water mains: chamber and direct-buried installation
On water networks gate valves sit untouched for years and then must close first time during a burst. The right design and installation method decide whether they do.
TAZ Engineering Team · · 6 min
Valve design
For cold water the standard is a ductile-iron resilient-seated gate valve with a non-rising stem, such as 30ch39r. The straight bore without a seat pocket does not trap sand, and the elastomer wedge achieves rate A tightness. Bodies are fusion-bonded epoxy coated inside and out; for drinking water the coating and rubber need approval for potable contact in the destination country.
Chamber or direct-buried
A valve in a chamber is accessible for inspection and repair, but chambers are expensive and flood or silt up. Direct burial is increasingly common: the valve is buried, a telescopic extension spindle reaches the stem cap and a surface box sits at ground level. This needs a non-rising stem, robust multiple stem seals and a durable external coating.
Operation and closing direction
Buried valves are operated with a key through the extension. Specify the closing direction (clockwise in most networks, though some utilities use anticlockwise) and the cap size. The number of turns to close should be on the datasheet so crews can confirm the valve is shut.
Maintenance
Exercising each valve regularly, for example once a year, prevents seizure. Keep a register with location, DN, turns, last exercise date and condition to speed up burst isolation.
Ordering
State DN, PN, installation type, burial depth for the extension, closing direction, coating requirements and drinking-water approval. TAZ will supply the valve and the buried-service kit.
Checklist
- DN and PN
- resilient wedge
- non-rising stem
- coating and potable approval
- chamber or buried
- burial depth
- extension and surface box
- closing direction
- turns to close
- exercising programme