Backup Power for Water & Wastewater Sites

What site teams need to know about generators, ATS, fuel, telemetry and emergency response

Water and wastewater sites depend on reliable power.

When electricity is interrupted, the impact can be more serious than a temporary inconvenience. Pumps can stop. Telemetry can be lost. Treatment processes can be disrupted. Emergency overflows may become more likely. Site teams may need to respond quickly, sometimes during storms, flooding or wider network disruption.

For water treatment works and wastewater pumping stations, backup power is not simply a “nice to have”. It is part of operational resilience.

A well-planned standby power system helps keep essential assets running during mains failure. It can support pumps, control panels, telemetry, instrumentation, lighting, security and other critical systems until the incoming supply is restored.

This article looks at what site teams, asset managers and electrical engineers should consider when planning backup power for water treatment and wastewater pumping stations, including generator sizing, automatic transfer switches, fuel autonomy, access constraints, telemetry, maintenance and temporary power during upgrades.

Why backup power matters on water and wastewater sites

Water infrastructure is often exposed to several risks at once.

A mains power failure may happen during poor weather, high rainfall, flooding or wider grid disruption. At the same time, the site may be managing increased flows, storm conditions or operational pressure elsewhere on the network.

For wastewater pumping stations, loss of power can stop pumps from moving flows through the system. For treatment works, power loss can affect process equipment, control systems and site monitoring. In both cases, the ability to maintain operation or recover quickly is essential.

The regulatory and public focus on storm overflows, emergency overflows and pollution incidents has also increased. Government guidance states that all storm overflows operated by water and sewerage companies in England are now fitted with event duration monitors, and that monitoring data should be used to inform daily operation, maintenance and upgrades to the sewerage system. (GOV.UK)

For site teams, this means backup power planning should not be seen in isolation. It sits alongside wider responsibilities around resilience, environmental protection, monitoring, maintenance and incident response.

What can happen when power fails at a pumping station?

A wastewater pumping station depends on power to move flow from one part of the network to another. If that power is lost, the impact depends on the station design, available storage, incoming flow, weather conditions and how quickly backup arrangements are activated.

Potential consequences can include

• Pumps stopping unexpectedly
• Rising wet well levels
• Loss of telemetry or control visibility
• Alarms being triggered
• Increased risk of emergency overflow operation
• Increased tanker or site response requirements
• Increased risk of pollution incidents
• Operational pressure on upstream or downstream assets

The risk is not always the same. A small site with limited incoming flow may have more time to respond than a heavily loaded pumping station during storm conditions. However, the principle is the same: the backup power arrangement needs to match the operational risk of the asset.

Environment Agency and Ofwat guidance on water industry regulation incidents notes that emergency overflows at some sewage pumping stations and wastewater treatment works are permitted for use in an “emergency” as defined by the permit, provided relevant permit conditions are met. It also states that if a water company becomes aware of a discharge entering water from an emergency overflow, it should be self-reported to the Environment Agency as an incident, because emergency overflows are high-risk assets from an environmental perspective. (Ofwat)

That makes power resilience especially important for sites where loss of power could increase the likelihood of an overflow or environmental incident.

What systems may need backup power?

One of the first steps in planning backup power is understanding what actually needs to stay operational.

On a water or wastewater site, the critical load may include more than the main pumps. Site teams should consider the full system, including controls, monitoring and safe access.

System or asset	Why it may need backup power
Duty and standby pumps	To maintain flow and reduce risk of storage being exceeded
Control panels	To manage pump operation, sequencing and protection
Telemetry and alarms	To maintain visibility and alert response teams
Level instruments	To monitor wet well or process levels
Motor control centres	To support controlled operation of electrical plant
Lighting	To allow safe access and emergency attendance
Security systems	To maintain site protection during an outage
Communications equipment	To support remote monitoring and escalation
Dosing or treatment equipment	To protect process continuity where applicable
Heating, ventilation or kiosk systems	To protect equipment and maintain safe operating conditions

Water UK’s specification for package wastewater pumping stations highlights that a pumping station includes more than pumps alone. It covers the wet well, valve chamber, pump units, valves, electrical equipment, controls, telemetry and kiosk. (water.org.uk)

That is a useful reminder: backup power needs to be planned around the complete asset, not just the largest motor.

Generator sizing: why pump starting loads matter

Correct generator sizing is critical on water and wastewater sites.

Pumps, motors and control equipment can create high starting currents. A generator that appears large enough for the running load may still be undersized if it cannot handle the starting demand of pumps or other motor-driven equipment.

When sizing a generator for a pumping station or treatment site, engineers need to understand:

• The running load of each pump or item of equipment
• Starting current requirements
• Whether pumps start direct-on-line, soft start or via variable speed drives
• Duty/standby arrangements
• Which pumps may need to run together
• Control panel and telemetry loads
• Any lighting, heating or auxiliary loads
• Whether the generator needs to support the whole site or only critical loads
• Future load growth or planned asset upgrades

Your existing generator sizing content already makes the point that businesses need to account for running and starting loads, especially where motors or compressors are involved. That principle is particularly important for pumping stations because pump start-up demand can be significantly higher than normal running demand.

An undersized generator can cause voltage dips, failed starts, nuisance trips or unstable operation. An oversized generator may increase capital cost, fuel use and long-term running issues if it regularly operates at very low load.

The right answer is a properly assessed generator size based on the site’s actual electrical demand and operational requirements.

Fuel autonomy: how long does the generator need to run?

Generator runtime is another key consideration.

For water and wastewater sites, it is not enough to ask, “Does the generator start?” Site teams also need to ask, “How long can it support the asset if the outage continues?”

Fuel autonomy should be based on site risk and operational response times. Important factors include:

• Criticality of the site
• Incoming flow rate
• Wet well storage time
• Weather and storm conditions
• Distance from fuel supply or response teams
• Access during flooding or severe weather
• Whether the site is remote or unmanned
• Expected generator load
• Fuel tank size
• Refuelling arrangements
• Fuel quality and storage condition

A generator may technically support the load, but if the fuel strategy is weak, the backup power plan may still fail. This is especially important for remote pumping stations or treatment sites where access may be difficult during storms or flooding. If fuel deliveries cannot reach the site, the generator’s practical runtime may become the limiting factor.

Fuel quality and contamination risk

Stored diesel can degrade over time, especially where generators are used infrequently. Water, sediment, microbial growth and poor storage conditions can all affect generator reliability.

For standby generators on water and wastewater sites, this risk is particularly relevant because fuel may sit unused for long periods. The generator may only be called on during a power cut, which is exactly the wrong time to discover fuel contamination.

Poor fuel condition can contribute to:

• Hard starting
• Blocked filters
• Reduced engine performance
• Increased smoke
• Fuel system damage
• Unplanned shutdown
• Failed generator start during an outage

This is why fuel testing, polishing and tank checks should be considered as part of the wider maintenance strategy. Your existing fuel management content already covers the risks of water, sediment and microbial contamination in stored diesel, making it a useful internal link from this article. For critical water and wastewater assets, fuel management should be treated as part of resilience planning, not just a maintenance task

Automatic transfer switches and changeover arrangements

An automatic transfer switch, or ATS, is often central to a reliable backup power system.

The ATS monitors the mains supply and transfers the electrical load to the standby generator when mains power fails. Once the mains supply returns and stabilises, the system can transfer back in a controlled way.

For water and wastewater sites, this automatic changeover can be important because many assets are unmanned or remotely monitored. If a site depends on manual intervention, the response time may be too slow during a live outage.

Key ATS considerations include:

• What load should transfer to generator power
• How quickly the generator needs to start
• Whether the system needs automatic or manual changeover
• How pump controls behave during transfer
• Whether alarms and telemetry remain live
• Whether there is a safe return-to-mains sequence
• Whether the ATS is tested as part of the maintenance regime
• How the system behaves after repeated power interruptions

The generator is only one part of the backup power system. If the ATS, controls or distribution arrangements are not correctly specified and maintained, the site may still be vulnerable.

Telemetry and remote monitoring

Telemetry is essential for modern water and wastewater operations. Site teams need to know when power has failed, when a generator has started, whether pumps are operating and whether levels are rising.

Backup power planning should therefore include telemetry and communications equipment, not just pumping plant.

A generator may keep the pumps running, but if the site loses communications, control teams may not have the visibility they need to manage risk. In some cases, telemetry may need UPS support to bridge short interruptions, support communications equipment or protect sensitive controls while the generator starts.

The government’s storm overflow guidance places significant emphasis on monitoring data and how it can inform operation, maintenance, upgrades and compliance. (GOV.UK)

For site teams, the practical message is simple: backup power should support visibility as well as operation.

Access, location and environmental constraints

Many pumping stations and treatment assets are not straightforward sites.

Generators may need to be installed or deployed in locations with limited access, restricted space, noise constraints, flood risk, uneven ground, security issues or challenging cable routes.

For permanent standby generators, site planning may need to consider:

• Vehicle and crane or Hiab access
• Generator base or plinth requirements
• Cable routes and connection points
• Fuel tank location and bunding
• Noise and acoustic enclosure requirements
• Ventilation and exhaust discharge
• Flood risk
• Security and vandalism protection
• Safe access for maintenance
• Safe access during poor weather
• Proximity to control kiosks and electrical panels

For temporary generator hire, the same issues still matter. The response may need to happen quickly, but the temporary setup still needs to be safe, correctly sized and practical for the site.

Pumping station design guidance also notes that parts of wastewater pumping stations can be hazardous zones under DSEAR considerations, so site-specific risk assessment is important where electrical or powered equipment is being installed or maintained. (water.org.uk)

Temporary generator hire during maintenance, upgrades or emergencies

Not every backup power requirement is permanent.

Water and wastewater sites may need temporary generator hire during:

• Planned electrical shutdowns
• Control panel upgrades
• Pump replacement works
• Generator servicing or replacement
• Treatment process upgrades
• Emergency power failures
• Flood or storm response
• Cable or switchgear works
• Site resilience improvements

Temporary power can help keep operations running while permanent infrastructure is maintained, replaced or upgraded.

For pumping stations, the temporary generator must be matched carefully to the site load and operational requirement. It may also need suitable cabling, distribution, fuel management, safe positioning and access planning.

In some cases, temporary generator hire can act as a bridge while a permanent generator replacement project is planned. This can be useful where an existing generator is ageing, unreliable or no longer sized correctly for the site.

Maintenance and testing: proving the system before it is needed

Backup power systems should not be assumed ready simply because the equipment is installed.

Routine maintenance and testing are essential. This includes the generator, ATS, batteries, fuel system, controls, alarms and any associated telemetry or UPS equipment.

A good maintenance programme may include:

• Routine generator servicing
• Battery checks
• Fuel testing and polishing
• ATS function testing
• Load bank testing
• Visual inspection of cables and connections
• Control panel checks
• Alarm and telemetry verification
• Run testing under suitable load
• Service reports and recommendations

The water sector is also under growing pressure to demonstrate proactive management of assets and pollution risk. From 2026, water companies are required to publish annual Pollution Incident Reduction Plans, setting out steps to reduce pollution incidents and their environmental impact. (GOV.UK)

Reliable backup power is only one part of that wider picture, but for critical sites it can be an important part.

Common backup power mistakes on water and wastewater sites

Backup power issues often come from small assumptions made early in the planning process.

Common mistakes include:

Mistake	Why it creates risk
Sizing only for running load	Pump starting currents may overload the generator
Ignoring telemetry and controls	Pumps may run, but visibility and alarms may be lost
Assuming manual changeover is enough	Unmanned sites may need automatic response
Not allowing enough fuel autonomy	Generator runtime may be too short for real outage conditions
Poor fuel maintenance	Stored diesel may degrade before it is needed
Not testing the ATS	Generator may work, but transfer may fail
Poor site access planning	Emergency response or refuelling may be delayed
No temporary power plan	Planned works or generator failure may leave the site exposed
No load testing	The generator may not be proven under realistic demand
Outdated site load information	Generator may no longer match the site’s actual needs

Avoiding these mistakes starts with a proper site assessment.

Practical checklist for site teams

When reviewing backup power for a water treatment works or wastewater pumping station, site teams should ask:

Question	Why it matters
What assets must remain powered during an outage?	Defines the critical load
What are the pump starting requirements?	Prevents undersizing
Is the generator sized for current and future demand?	Avoids capacity issues
Is automatic changeover required?	Supports unmanned or remote sites
How long does the generator need to run?	Defines fuel autonomy
Is fuel quality being tested?	Reduces risk of generator failure
Are telemetry and alarms backed up?	Maintains operational visibility
Can engineers and fuel deliveries access the site?	Supports emergency response
Has the generator been tested under load?	Proves performance
Is there a temporary power plan?	Supports upgrades and emergencies
Are records available for audits and reviews?	Supports compliance and asset management

This table could work well on the website as a simple visual checklist.

How P&I Group can help

P&I Group supports water, wastewater and utility sites with practical, engineer-led critical power solutions.

We can help assess, install, maintain and support backup power systems for treatment works, pumping stations and wider utility infrastructure.

Our support can include:

• Standby generator supply and installation
• Temporary generator hire
• Generator sizing and site surveys
• ATS and changeover support
• Generator servicing and maintenance
• Load bank testing
• Fuel testing, polishing and fuel management
• Emergency response
• Generator replacement planning
• UPS support for controls, telemetry or sensitive equipment
• Critical power reviews for water and utility sites

Whether you are planning a permanent standby generator, reviewing an ageing asset, arranging temporary power during upgrades or improving resilience across multiple sites, the right backup power plan can reduce operational risk.

In Summary

Backup power for water treatment works and wastewater pumping stations needs to be practical, site-specific and properly maintained.

It is not just about placing a generator on site. The system needs to be correctly sized, safely connected, fuelled, tested and integrated with controls, telemetry and emergency response procedures.

For wastewater pumping stations, power resilience can help reduce the risk of pump failure, loss of visibility and emergency overflow events. For treatment works, it can support process continuity, site safety and operational recovery during outages.

The best backup power plans start with a clear understanding of the site, the critical loads, the likely outage scenarios and the consequences of failure.

Speak to P&I Group about backup power for water and utility sites.

FAQs

Need backup power support for a water or wastewater site?

P&I Group supports water, wastewater and utility sites with generator hire, standby generator installation, servicing, fuel management, ATS support and emergency response.

Speak to P&I Group about backup power for water and utility sites.