WaterBoost Compact
WaterBoost WB-Compact 4.5 ACW1 – Accumulator Booster Pump (Wall Mounted)
- Established 1975
- Trusted by thousands of customers
The WaterBoost WB-Compact 4.5 ACW1 is a wall-mounted, variable-speed accumulator booster pump. Paired with an external accumulator or pressure vessel it delivers up to 4.5 bar of smooth, constant pressure to showers, taps and appliances — the pump handles pressure, the vessel handles peak flow. Fits GWS, WaterBoost, Lowara, Grundfos and Stuart Turner vessels, vertical or horizontal, and can sit away from the vessel for a tidy install.
Suitable for heat pump systems. Paired with an accumulator vessel, gives an unvented hot water cylinder the pressure and stored flow it needs where the mains supply falls short.
Wall mounting keeps the floor clear where space is tight. Pressure is set on the LCD display; built-in WiFi and the DAB DConnect app give remote control, wireless updates and optional Google Home and Alexa voice control. WRAS approved and exceptionally quiet.
Accumulator ready
LCD control
Google · Alexa
Quiet running
More about this product
Key Features
Improved – Features a new three-rotor hydraulic design with wireless update capability, allowing future performance and functionality enhancements.
Constant – Advanced inverter technology automatically regulates pump speed to maintain smooth, consistent water pressure.
Efficient – Variable-speed motor technology delivers energy savings of up to 50% compared with conventional fixed-speed pumps.
Quiet – Housed in a sound-absorbing casing with anti-vibration design, operating at just 45 dB(A) at 1 metre.
Simple – Designed for straightforward wall-mounted installation, intuitive setup, and easy day-to-day operation.
Compact – Space-saving wall-mounted footprint measuring 439 × 263 × 236 mm (H × W × D) and weighing only 15 kg, ideal for tight installation spaces.
Reliable – WRAS approved for potable water use and backed by a three-year manufacturer’s guarantee.
Standard delivery:
Standard delivery is free on most orders. Some items may incur a delivery charge depending on weight, size or value. Any applicable charge will be displayed at checkout.
Deliveries will typically be made between 7am and 6pm, Monday to Friday (excluding public holidays).
Next day delivery:
Next working day delivery is available for a £16.50 + VAT delivery charge.
Orders must be placed before 12 noon to qualify for next working day delivery. Orders placed after 12 noon on Thursday but before noon on Friday will be delivered the following Monday. Orders placed after 12 noon on Friday will be delivered on Tuesday.
Pallet/Large/Difficult items:
Some large, heavy or difficult to transport items may incur an additional delivery charge. Please contact us for a delivery quote before ordering.
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Frequently Asked Questions
Quick answers to common questions about the WaterBoost WB-Compact 4.5 ACW1 – Accumulator Booster Pump (Wall Mounted). For technical specifications, see the product details above; for sizing or installation advice, contact our team. If you have any other questions, we're happy to help.
What is an accumulator tank?
An accumulator tank is a pressurised vessel that connects directly to the mains supply and stores water under pressure. When a tap or shower opens, water discharges immediately from the vessel at full mains pressure rather than drawing only from the street main. This delivers stronger, more consistent flow at peak times. Accumulators have no pump and no moving parts so they are maintenance free and silent.
When should I use an accumulator instead of a pump?
An accumulator is the right solution when static mains pressure is adequate – above 2 bar – but flow is poor or drops during peak demand. It boosts available flow without adding a pump, energy use or noise. If static pressure is below 2 bar, a booster pump is needed instead, or an accumulator combined with a charge pump such as the WaterBoost ACF1.
What size accumulator do I need?
Accumulators are typically sized on a 60 per cent usable rule – a 300 litre vessel delivers around 180 litres of boosted water per cycle. As a guide, a 2 to 3 bedroom home suits a 300 litre vessel such as the GWS GCB-300LV. Larger 4 to 5 bedroom homes or properties with multiple bathrooms typically need 450 to 600 litres. Vertical models save floor space, horizontal models suit lofts and roof spaces.