Valve Operations on Live Mains

Valve operations on live water and gas mains involve opening, closing, or throttling valves on pressurised pipes.
Incorrect valve operation can cause water hammer, pressure surges, and pipe burst affecting the network.
Water main valve operation can disrupt supply to thousands of customers and affect fire hydrant availability.
Gas valve operations on live mains carry explosion risk if valves are operated incorrectly or too quickly.
Valve chambers are often below ground in manholes — confined space and manual handling hazards apply.
Valve keys and operating handles can be heavy and require significant physical effort to turn.
Cross-contamination of the potable water supply can occur if valves are operated in the wrong sequence.
Network operators must authorise and often supervise valve operations on their distribution systems.
Communication with the network control centre is essential throughout multi-valve operations.
Some valves have been closed for years and may seize, break, or leak when operated.

Network disruption	Incorrect valve operation causes loss of supply, pressure transients, and burst mains affecting communities.
Explosion risk	Gas valve operations on live mains can cause uncontrolled gas release and potential explosion if mishandled.
Confined space	Most network valves are in underground chambers requiring confined space assessment before entry.

Do

Don't

Obtain authorisation from the network operator before operating any valve on their system
Follow the valve operation sequence specified by the network control centre precisely
Assess valve chambers for confined space hazards before opening covers and descending
Communicate with the control centre throughout multi-valve switching operations
Operate valves slowly to prevent water hammer and pressure surges in the network
Use the correct valve key or handle for the valve type and size being operated
Confirm the valve identity and number before operating — wrong valve operations are common
Wear appropriate PPE including gloves and eye protection when operating valves
Report any seized, broken, or leaking valves to the network operator immediately
Complete manual handling assessment for operating stiff or heavy valve mechanisms

DON'T operate network valves without authorisation from the network operator
DON'T slam valves open or closed — operate slowly to prevent pressure transients
DON'T enter valve chambers without confined space assessment and gas monitoring
DON'T operate the wrong valve — always confirm the identity and number before turning
DON'T deviate from the switching sequence specified by the control centre
DON'T force a seized valve — report it for specialist attention rather than risking breakage
DON'T leave valve chambers open and unattended — guard them to prevent public falls
DON'T operate gas valves without understanding the network pressure and flow consequences
DON'T assume old valves will operate smoothly — they may leak, break, or seize
DON'T carry out multi-valve operations without continuous communication with network control

See also: Water Main Installation Safety | Gas Main Installation Safety

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