Water Hammer

Understanding Water Hammer

Water hammer is a serious issue in South Africa’s water networks, particularly in municipalities where ageing infrastructure and high-pressure systems are common. It occurs when the forward velocity of water in a pipeline is suddenly decelerated—for example, when a valve is closed too quickly. This sends a shock wave through the pipe, creating hammering noises and potentially damaging pipes, pumps, and fittings.

The shock wave can cause localised spikes in pressure, which travel along the pipeline until the energy dissipates. Over time, repeated surges can lead to fatigue failures, bursts, and costly repairs challenges South African utilities are already struggling to manage.

Reducing Water Hammer

The risk of water hammer can be greatly reduced by:

• Operating valves in a controlled, slow manner
• Using automatic valve systems designed to absorb or prevent surges
• Selecting the correct valve type for each application
• Key Valve Solutions for South African Networks

Air Valves

• Prevent vacuum conditions during pump trips or water column separation
• Allow controlled air intake and release to dampen pressure surges
• Essential for long pipelines and pump stations in rural and urban areas
• Automatic Control Valves (Series 869)
• Surge anticipating valves detect high-pressure events in pumped systems
• Automatically open to relieve pressure, then close slowly to prevent hammering
• Ideal for municipalities with large pumping operations, such as Johannesburg Water or Umgeni Water

Non-return Valves

• Prevent reverse flow into pumps, wells, or intakes
• Correct valve selection is critical in high-flow reversal scenarios
• Hydraulic dampers can cushion valve closure, reducing check valve slam

Pressure Wave Surges in South African Systems

When pumps stop suddenly, reverse flow can slam check valves shut, creating loud hammer noises and stretching pipes under extreme pressure.

This surge can cause:

• Pipe cracks and bursts
• Cavitation and implosion from vacuum pressures
•  Long-term fatigue failures from repeated surges

Given South Africa’s reliance on ageing infrastructure, these risks are particularly high in municipalities where pump reliability is inconsistent.

Safe and Trouble-Free Operation -To prevent check valve slam:

• Valves should close quickly enough to stop reverse flow, or slowly with hydraulic dampers to cushion closure
• Pump systems must be assessed for suitability to handle reverse spin and flow
• Proper valve selection and maintenance are essential to protect upstream fittings and extend asset life

Why This Matters for South Africa

• Supports DWS priorities on reducing non-revenue water and protecting infrastructure
• Extends lifespan of ageing pipelines in metros and rural towns
• Reduces costly repairs from bursts and fatigue failures
• Improves reliability of water supply for communities under stress from drought and demand growth

Contact AVK South Africa
For technical guidance on preventing water hammer and improving network efficiency, contact David Hurley directly. Call him or click the email icon to connect.