In short

  • Sizing a commercial booster system means matching flow rate, pressure, storage and control to the building — not just picking a high-pressure pump.
  • Get the incoming supply, break-tank requirement and pump configuration right before anything else.
  • Both oversizing and undersizing carry a cost; the specification you start with determines reliability and running cost for years.

Reliable water pressure is essential in any commercial building. Whether the project involves an apartment block, hotel, office, school, care facility, hospital or industrial site, the water supply must be capable of meeting demand throughout the building, including at the busiest times and at the highest or most remote outlets.

Where the incoming supply cannot provide the required flow and pressure, a commercial booster system may be needed. However, selecting the right system involves much more than choosing a pump with a sufficiently high pressure rating.

1What Does A Commercial Booster System Do?

A commercial water booster system increases and regulates the pressure within a building’s cold water distribution system. It will typically include one or more pumps mounted on a common base, together with suction and discharge manifolds, valves, pressure sensors, controls and associated safety equipment.

Depending on the project, the booster set may draw water from:

The purpose is not simply to create the highest possible pressure. It is to deliver the required flow rate at a controlled pressure, wherever and whenever water is being used.

2Start With The Required Flow Rate

The first consideration is the building’s peak water demand. This is not normally calculated by adding together the maximum flow from every tap, shower, WC, appliance and outlet. In most buildings, not every outlet will operate simultaneously. Instead, the design should account for probable simultaneous demand based on factors such as:

A hotel, for example, may experience a concentrated period of demand during the morning. An office building may have a lower but more consistent requirement, while an industrial application could include machinery or processes with clearly defined flow rates. This is why booster-system selection should be based on a calculated design flow rather than a rough estimate or the maximum capacity shown on a product data sheet.

Booster-system selection should be based on a calculated design flow — not a rough estimate, and not the maximum capacity printed on a product data sheet.

3Calculate The Pressure Requirement

Once the design flow has been established, the next step is to determine the pressure the system must provide. The required pump head will usually need to account for:

In simplified terms:

Required pump head = static lift + required outlet pressure + system losses – usable inlet pressure

The calculation must be made at the required design flow. A pump may be capable of producing a high pressure when very little water is moving, but its available pressure will reduce as the flow rate increases. The correct booster set must therefore achieve the required flow and pressure at the same operating point.

4Assess The Incoming Water Supply

The performance of the incoming supply should be established before a booster system is selected. A static pressure reading alone is not enough. Static pressure is measured when no water is flowing and can appear perfectly adequate even when the available flow rate is limited. The investigation should consider:

Where the incoming main cannot support the building’s peak demand, a cold water storage tank can provide a buffer between the incoming supply and the booster pumps. The tank fills at the rate available from the main, while the booster system draws from the stored water to satisfy periods of higher demand.

Pumps and boosters drawing more than 12 litres per minute from a supply pipe are generally classed as notifiable work under the Water Supply (Water Fittings) Regulations. The proposed installation and method of connection should therefore be checked with the relevant water undertaker.

5Does The System Need A Break Tank?

Many commercial booster installations use a break tank or dedicated cold water storage tank. This can:

The tank should not simply be sized according to the maximum flow rate of the pumps. Its usable capacity should reflect the incoming refill rate, anticipated peak demand, duration of peak usage and the operational requirements of the building.

Water turnover is also important. Excessively large tanks can result in unnecessary storage and reduced turnover, while a tank that is too small may empty during peak demand. Tank access, insulation, overflow arrangements, inlet control, cleaning and ongoing water hygiene must all be considered as part of the design.

For projects with limited plant-room access, tanks may be supplied as one-piece, two-piece or sectional configurations. Packaged booster systems can also be supplied with the booster set, tank, valves and connecting pipework assembled as an integrated solution.

6Single, Twin Or Triple Pump Booster Set?

Commercial booster systems are commonly supplied with one, two or three pumps, although larger systems can incorporate additional pumps. The correct arrangement depends on both the required capacity and the importance of maintaining the water supply.

Single-pump systems

A single-pump booster set can be suitable for smaller or less critical applications where one pump can meet the full design duty. It is generally the simplest and most compact option, but it provides no pump redundancy. If the pump is unavailable because of a fault or maintenance, the boosted supply will also be unavailable.

Twin-pump systems

A twin-pump set can be configured in several ways. In a duty/assist arrangement, one pump meets lower demand and the second pump starts when additional flow is required. Alternatively, both pumps may be selected so that either can provide the required duty, creating a duty/standby arrangement with greater resilience. Automatic pump alternation can also balance operating hours and reduce the risk of one pump remaining unused for long periods.

Triple-pump systems

Triple-pump systems are often used for larger buildings, higher flow rates or applications requiring greater resilience. They can operate as duty/assist/assist systems, with additional pumps brought into operation as demand rises. They may also be configured to retain standby capacity should one pump become unavailable.

The system should be selected according to the building’s acceptable level of risk. An office, hotel, hospital and manufacturing facility may each require a different level of redundancy, even where their calculated flow rates are similar.

7Fixed-Speed Or Variable-Speed Control?

Traditional fixed-speed booster sets switch pumps on and off in response to changes in pressure. These systems can still be appropriate for some applications, particularly where demand is relatively stable or where a straightforward control arrangement is preferred.

However, demand in many commercial buildings changes continually. A variable-speed system can adjust pump speed to maintain the selected pressure as water usage rises and falls. Potential benefits include:

Variable-speed operation does not remove the need for correct pump selection. A badly oversized variable-speed pump may still operate inefficiently at low demand. The pumps should be selected so that the expected operating range remains within a suitable part of their performance curves.

8Horizontal Or Vertical Multistage Pumps?

Commercial booster sets frequently use horizontal or vertical multistage centrifugal pumps. Horizontal multistage pumps can provide a compact and cost-effective solution for lower and medium duties. Vertical multistage pumps are often selected where higher flows or pressures are required, or where plant-room floor space is restricted. Their vertical construction can provide a relatively small footprint while allowing several hydraulic stages to generate the required pressure.

The final choice should consider:

For wholesome water applications, all relevant components should be suitable for contact with drinking water. Stainless-steel pumps and manifolds are widely used because of their durability and corrosion resistance, but the complete installation – not only the pump casing – should be assessed.

9Controls, Protection And Building Management

The control system is a major part of a commercial booster set. Depending on the application, useful control and protection features may include:

For critical applications, the design should avoid unnecessary single points of failure. This may influence the number of pressure transducers, the control architecture and whether each pump has its own drive and protection. The required BMS signals and remote alarms should be agreed before the equipment is ordered rather than treated as an afterthought during installation.

10Consider The Plant Room And Installation Conditions

A technically suitable booster set may still be unsuitable if it cannot be installed, accessed or maintained properly. The site assessment should include:

The electrical supply is particularly important. Smaller systems may be available with a single-phase supply, while larger commercial booster sets will normally require three-phase power.

Pipework should be correctly sized and supported. Poor suction conditions, undersized pipework or excessive restrictions can reduce pump performance and increase the risk of noise, vibration and cavitation. Where possible, the booster set should have a positive, unrestricted supply from the storage tank, with suitable low-level protection to prevent dry running.

11Avoid Oversizing The Booster System

Selecting a larger system “to be safe” can create its own problems. An oversized booster set may:

A sensible allowance for uncertainty or future development may be appropriate, but this should be engineered into the design rather than added as an arbitrary percentage. Where significant future demand is expected, a modular system that can stage multiple pumps may offer a better solution than installing one unnecessarily large pump.

12Look Beyond The Initial Purchase Price

The lowest-cost booster set is not always the most economical choice over its working life. Whole-life considerations include:

A properly selected system should operate efficiently across the building’s normal demand range while still meeting its peak requirement. It should also be possible to isolate, inspect and service the equipment without creating unnecessary disruption.

13Information Needed To Select A Commercial Booster System

Providing accurate project information at the beginning allows a booster-system supplier to recommend equipment with greater confidence. Useful information includes:

Where some of this information is not yet available, an experienced supplier can work with the project team to identify what needs to be measured or calculated before equipment is selected.

14Get The Specification Right From The Start

The right commercial booster system is one that delivers the required flow and pressure without being unnecessarily large, complex or expensive. Its design should bring together the hydraulic duty, incoming supply, storage requirements, controls, resilience, installation conditions and long-term maintenance needs.

Need help specifying a commercial booster system?

Bespoke Water Solutions offers far more than the supply of commercial booster equipment. Drawing on more than 35 years of industry experience, our team can assess your existing water system, identify pressure, flow or storage issues and design a solution around the specific requirements of your building or application — from offices, hotels and apartment developments to healthcare facilities and industrial sites.

Solutions can include single, twin and triple-pump booster sets, variable-speed controls and fully packaged systems with WRAS-approved GRP cold water storage tanks. Larger and fully bespoke water systems can also be designed to meet more complex project requirements.

For straightforward, unbiased advice or assistance selecting a commercial booster system, get in touch or call us on 01226 782049.

Written by the team at Bespoke Water Solutions, drawing on more than 35 years of experience with water systems, booster applications and bespoke packaged solutions.