What Size Pumping Station Do I Need for a Housing Development?

For a new housing development, establishing the correct pumping station size is an important part of the drainage design.

Whether the scheme involves 20 homes or several hundred, the required pumping station depends on more than the number of properties being served.

Wastewater flows, site levels, rising main length, storage requirements and the intended adopting organisation can all influence the final design.

The risk comes when a pumping station is sized around early assumptions before those requirements have been fully established. Changes later in the project can affect pump selection, wet well dimensions, civil works and technical approval.

For developers, consultants and groundworkers, the key is to consider the pumping station alongside the wider drainage infrastructure before important design decisions become fixed.

How is a pumping station sized for a housing development?

Pumping station sizing begins with understanding the development and the wastewater flows it needs to manage.

The design then needs to establish:

• Design flow: The expected wastewater contribution and required pumping discharge.
• Pump duty: The flow the pumps must deliver against the calculated total dynamic head.
• Wet well operating volume: The capacity needed to manage normal pump cycles.
• Emergency storage: The additional capacity required during pump or power failure.
• Rising main design: The pipe diameter, length, levels and hydraulic losses.
• Adoption requirements: The standards of the intended Water Authority or NAV.

These factors are connected.

A change to the rising main route can affect pump duty. A change to incoming sewer levels can affect wet well depth and available storage. Different adopting organisations may also require different equipment or hydraulic arrangements.

That is why the complete pumping station should be considered before pumps or chamber dimensions are finalised.

What size pumping station is needed for 100 or 150 homes?

The number of homes helps establish the design flows and emergency storage requirements, but it does not determine the complete pumping station size.

For example, two developments of 150 homes may require very different pumping arrangements if one has a longer rising main or a greater static lift to the discharge point.

One calculation that can be estimated from dwelling numbers is emergency storage.

For qualifying foul pumping stations serving fewer than 500 dwellings, Water UK’s Design and Construction Guidance (DCG) includes a minimum emergency storage criterion of 160 litres per dwelling.

Using that criterion:

• 50 homes: 8,000 litres (8 m³)
• 100 homes: 16,000 litres (16 m³)
• 150 homes: 24,000 litres (24 m³)
• 200 homes: 32,000 litres (32 m³)

These figures are illustrative emergency storage requirements, not the total wet well volume or pump capacity.

The actual storage arrangement must satisfy the current applicable guidance and the intended adopting organisation’s requirements. Suitable upstream sewer capacity or separate storage structures may be needed.

How is pump capacity calculated?

Once the design wastewater flow has been established, engineers need to calculate the head the pumps must overcome.

This is known as total dynamic head and includes:

• Static head: The vertical hydraulic lift between the relevant wet well and discharge levels.
• Friction losses: Resistance as wastewater travels through the rising main.
• Local losses: Additional resistance through valves, bends and fittings.

For a simplified system:

Total Dynamic Head = Static Head + Friction Losses + Local Losses

For example, if the static head is 7 metres, rising main friction losses are 3 metres and valve losses are 1 metre, the total dynamic head would be 11 metres.

If the required pumping flow is 10 litres per second, the preliminary duty would be 10 l/s at 11 metres head.

This is an illustrative calculation rather than a design for a particular development.

The selected pumps must then be checked against their performance curves, the complete hydraulic system and the applicable adoption requirements.

Why wet well and rising main design matter

Pump capacity is only part of the calculation.

The wet well needs sufficient operating volume to manage pump starts and running time, while avoiding unnecessarily long wastewater retention.

The rising main also affects the duty and operation of the station. Its length, diameter, route and levels influence friction losses, velocity and the time wastewater remains within the system.

The design therefore needs to balance:

• Pumping flow and total dynamic head.
• Wet well operating volume and emergency storage.
• Pump starting frequency.
• Rising main velocity and wastewater retention.
• Long-term maintenance and operational requirements.

A larger wet well or rising main is not automatically a better solution.

For example, increasing the rising main diameter may reduce friction losses but increase wastewater retention time. Similarly, increasing the wet well volume can reduce pump cycling while creating septicity concerns.

These decisions need to be developed together rather than treating each element as a separate design exercise.

Adoption requirements should be considered early

Where a pumping station is intended for adoption, the future asset owner’s requirements can influence the size and arrangement of the entire station.

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

These can affect:

• Pump selection and hydraulic duty.
• Emergency storage.
• Wet well and valve chamber arrangements.
• Rising main design.
• Electrical controls and telemetry.
• Access and maintenance provisions.

If the proposed adopter changes after the design has progressed, the pumping station may need to be reviewed against different requirements.

Advantage works with developers, consultants and groundworkers to identify these considerations early and develop pumping station solutions around the intended adoption route.

Explore Water Authority & NAV Pumping Station Guidance

When should you involve a pumping station specialist?

Ideally, once it becomes clear that pumped drainage will be required, but before the detailed civil design and drainage layout have been fixed.

At that stage, a technical review can help establish:

• What information is needed to complete the hydraulic design.
• Whether the proposed pumping station location is suitable.
• How the rising main affects the required pump duty.
• What emergency storage needs to be allowed for.
• Which Water Authority or NAV requirements may influence the design.

Early involvement does not mean every aspect of the pumping station needs to be fully designed immediately. It means understanding the requirements while there is still flexibility to accommodate them.

Working on a housing development?

If your development requires a sewage pumping station but the hydraulic requirements, storage or adoption route are still being established, this is a good point to involve Advantage.

Our engineers can work alongside your consultant and groundworker to review the design requirements and help develop a pumping solution that fits the wider development.

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