How Many Pump Starts per Hour Should an Adoptable Pumping Station Have?

The number of times a sewage pump starts each hour is an important part of adoptable pumping station design.

If a pump starts too frequently, it can increase wear on motors, starters and mechanical equipment, potentially affecting long-term reliability and maintenance costs.

However, reducing pump starts is not simply a case of increasing the wet well size. The design also needs to consider pump running time, wastewater retention, control levels and the requirements of the intended adopting organisation.

For developers, consultants and groundworkers, the key is making sure the pumps, wet well and controls are designed together rather than treating pump cycling as a separate calculation.

What is the maximum number of pump starts per hour?

For relevant adoptable pumping stations, Water UK’s Design and Construction Guidance (DCG) specifies a maximum of 15 pump starts per hour, with a minimum pump running time of 60 seconds.

However, this does not mean every pumping station should be designed to achieve 15 starts per hour.

The permitted starting frequency can depend on:

• Pump and motor manufacturer requirements.
• Motor size and starting method.
• Pump discharge rate and incoming wastewater flow.
• Wet well operating volume.
• Duty and standby pump arrangements.
• Water Authority or NAV requirements.

Some adopting organisations apply stricter limits.

For example, Yorkshire Water’s published Local Practice has specified lower starting frequencies for certain non-framework pumps, depending on motor size.

The important point is to establish the relevant requirements before the pumps and wet well dimensions are finalised.

How are pump starts per hour calculated?

Pump starting frequency depends on how quickly wastewater enters the wet well and how quickly the selected pump removes it.

For a simplified single-pump, fixed-speed arrangement, the cycle time can be estimated using:

T = V/q + V/(Q − q)

Where:

• T = time between pump starts, in seconds.
• V = wet well operating volume, in litres.
• q = incoming wastewater flow, in litres per second.
• Q = pump discharge rate, in litres per second.

The number of starts per hour is then calculated as:

Starts per hour = 3,600 ÷ T

Example pump cycling calculation

Consider a pumping station with:

• Pump discharge rate: 12 l/s.
• Incoming wastewater flow: 6 l/s.
• Wet well operating volume: 1,800 litres.

The wet well takes 300 seconds to fill and a further 300 seconds to draw down while wastewater continues entering.

That gives a total cycle time of 600 seconds.

3,600 ÷ 600 = 6 starts per hour.

Under these simplified conditions, the pump would start approximately six times per hour.

The calculation provides a starting point, but an actual adoptable pumping station also needs to account for changing inflows, multiple pumps, control arrangements and equipment-specific limits.

Why wet well sizing matters

The wet well operating volume directly influences how frequently the pumps start.

A smaller operating volume generally results in more frequent cycling. Increasing that volume can reduce the number of starts, but it may also increase the time wastewater remains within the system.

This creates a balance between:

• Keeping pump starts within permitted limits.
• Achieving suitable minimum running times.
• Avoiding excessive wastewater retention.
• Maintaining appropriate pump submergence.
• Providing reliable duty and standby operation.

Long retention periods can increase the risk of septicity, odours and maintenance problems.

The DCG also includes a combined wet well and rising main retention criterion of no more than six hours for relevant adoptable pumping stations.

Simply increasing the wet well size to reduce pump starts may therefore create other design issues.

Pump controls need to be considered alongside the hydraulics

For adoptable foul water pumping stations, duty and standby pumps are commonly used to maintain resilience if one pump becomes unavailable.

The control arrangement determines when each pump starts, stops and takes over duty.

The design needs to consider:

• Duty pump start and stop levels.
• Standby pump activation.
• Pump alternation.
• High-level alarms.
• Minimum running times.
• Electrical starting arrangements.

These decisions affect the wet well operating volume and the performance of the wider pumping station.

This is where coordination between hydraulic and M&E design becomes important.

At Advantage, we work alongside consultants and groundworkers to help ensure the pumping equipment, control philosophy and wet well arrangement are developed together.

Our manufacturer-independent approach also gives us flexibility to select suitable equipment around the actual hydraulic and operational requirements of the site.

Adoption requirements should be established early

Where a pumping station is intended for adoption, the future asset owner may have specific requirements for pump cycling, equipment selection, controls and telemetry.

Water Authorities can apply approved Local Practices alongside the national DCG, while NAVs may have their own technical and operational requirements.

If those requirements are identified after the pumps or wet well have already been specified, the design may need to be revised.

A change to the selected pump, for example, can affect its discharge rate and permitted starting frequency, which may then influence the operating levels and required wet well volume.

The earlier these interfaces are considered, the easier it is to develop a coordinated pumping station design.

Explore Water Authority & NAV Pumping Station Guidance

See how this works in practice

At Avant Homes’ Bishops Quarter development in Leeds, Advantage delivered both foul and surface water adoptable pumping stations serving 150 new homes.

The project required the pumping systems to meet Yorkshire Water’s technical and adoption requirements while remaining aligned with the wider development programme.

Our team supported the design and delivery process through to installation and commissioning, coordinating the equipment and technical requirements with the project team.

Although the published project information does not specify the actual pump starting frequencies, it demonstrates the wider principle: pump selection, operating arrangements and adoption requirements need to be considered together rather than in isolation.

Read the Bishops Quarter Case Study

Working on an adoptable pumping station design?

If the pump selection, wet well operating volume or control arrangements have not yet been fully resolved, this is a good point to involve Advantage.

Our engineers can work alongside your consultant and groundworker to review the hydraulic requirements, assess suitable equipment and help coordinate the design around the intended adopting organisation.

Discuss Your Pumping Station Design