WaterBoost – CAT 5 range
WaterBoost WB-INT CAT 5 Slimline 300 Variable Speed 2402310CT5
- Established 1975
- Trusted by thousands of customers
The WaterBoost WB-INT CAT 5 Slimline 300 is the fluid category 5 version of our WB-INT Slimline 300: the same complete, pre-built variable-speed boosting system, fitted with a Type AB air gap and weir overflow grille so it can be connected to the mains where the Water Regulations demand Cat 5 backflow protection. A 300-litre WRAS-approved upright slimline tank with the DAB Esybox Diver internal variable speed pump delivers up to 100 litres per minute at up to 5 bar, in a format that fits through a standard doorway.
Cat 5 protection built in. The screened weir overflow sits above the spillover level, so the tank itself provides the air gap. No separate break tank or RPZ valve, and no annual RPZ test.
The Esybox Diver sits inside the tank, making the system exceptionally quiet and compact. It connects directly to the mains via the pre-fitted ¾” float valve, and WiFi connectivity via the DConnect app enables remote monitoring and voice control via Google Home and Amazon Alexa.
At 600mm diameter × 1200mm high, the Slimline tank is ideal for a plant room, garage, utility room or under stairs. It arrives fully pre-assembled with the PWB-2LX expansion vessel; the overflow needs piping to a visible drain on site. The tank carries a 5-year warranty and the pump a 3-year DAB warranty. Please contact us for delivery timescales.
WRAS tank & pump
WiFi · Google · Alexa
Internal pump
Direct mains
Pre-assembled
PWB-2LX expansion vessel
5yr tank · 3yr pump
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More about this product
Product overview
The WaterBoost WB-INT CAT 5 Slimline 300 is a complete boosted water system for premises where the incoming mains must be protected against backflow to fluid category 5, the highest level in the Water Supply (Water Fittings) Regulations 1999. It takes the WB-INT Slimline 300, our 300-litre upright tank with the DAB Esybox Diver variable speed pump inside it, and adds a Type AB air gap with a screened weir overflow grille, so the tank itself becomes the backflow protection.
Water enters from the mains through the pre-fitted ¾″ float valve, falls through the air gap into the tank, and is drawn from there by the Esybox Diver at up to 100 litres a minute and 5 bar. Nothing downstream of the tank can ever reach the mains. It suits commercial, agricultural, medical and horticultural premises that a water company would otherwise require to fit a separate break tank or an annually tested RPZ valve.
What Cat 5 means
The Water Regulations grade water by how harmful it would be if it were drawn back into the public supply. Fluid category 5 is water that could carry a serious health hazard: anything that has been in contact with animals, soil, chemicals, sewage, medical waste or industrial processes. Where a supply feeds outlets like that, the regulations require a physical break between the mains and the system, not just a valve.
A Type AB air gap is the accepted way to provide that break in a tank. The float valve discharges above the water, and a weir overflow with a screened grille is set below the valve outlet so the tank can never fill high enough to reach it, even with the float valve stuck open and the overflow running. The WB-INT CAT 5 has this built in, so the whole installation is compliant as delivered, with no separate break tank, no RPZ valve and no annual RPZ inspection.
Key features
Where Cat 5 is required
Technical specifications
| Model | WaterBoost WB-INT CAT 5 Slimline 300 |
| Part code | 2402310CT5 |
| Backflow protection | Fluid category 5 — Type AB air gap with screened weir overflow grille |
| Tank | 300 L upright slimline, WRAS approved |
| Tank dimensions | 600 mm diameter × 1,200 mm high |
| Pump | DAB Esybox Diver, variable speed, submerged in tank |
| Maximum flow | 100 l/min |
| Maximum pressure | 5 bar |
| Mains inlet | ¾″ float valve, pre-fitted |
| Overflow | Screened weir overflow — to be piped to a visible discharge point on site |
| Expansion vessel | GWS PressureWave PWB-2LX, supplied |
| Power supply | 230 V single-phase |
| Connectivity | WiFi, DAB DConnect app, Google Home and Amazon Alexa |
| Approvals | WRAS-approved tank and pump; Water Supply (Water Fittings) Regulations 1999 fluid category 5 |
| Warranty | Tank 5 years, pump 3 years (DAB) |
| Delivery | Fully pre-assembled; please contact us for timescales |
Frequently asked questions
Do I need the Cat 5 version or the standard WB-INT 300?
For a normal house feeding taps, showers and a hot water cylinder, the standard WB-INT Slimline 300 is fine. You need Cat 5 where the boosted water feeds outlets that could contaminate it: animals, irrigation, medical, laboratory, vehicle washing or industrial processes, or where your water company has asked for fluid category 5 protection. If in doubt, ask them or ask us.
What does the grille do?
It’s the screened weir overflow of the Type AB air gap. It sits below the float valve outlet, so the water level can never rise to the valve even if the valve fails open. The screen stops insects and debris getting into the tank. The overflow must be piped to a visible discharge point so a running overflow is noticed.
Does it replace an RPZ valve?
Yes. A Type AB air gap is the alternative to an RPZ valve for Cat 5 and doesn’t need the annual test and certificate that an RPZ does.
Is it noisy?
No. The Esybox Diver runs submerged in the tank, which muffles it almost completely. It’s one of the quietest boosting systems we sell.
Is 300 litres enough?
The tank buffers demand rather than storing a day’s water; the float valve refills it continuously from the mains. 300 litres suits premises drawing up to around 100 l/min in bursts. For heavier or longer draw-offs, look at the WB-INT Slimline 500.
Can you install it?
Yes, our own engineers install WaterBoost systems across Suffolk, Norfolk, Essex and Cambridgeshire. Ask us for a quote when you order.
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DAB Esybox Diver PDFDownload
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Data Sheet PDFDownload
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Manual PDFDownload
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-INT CAT 5 Slimline 300 Variable Speed 2402310CT5. 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 a mains pressure boosting system?
A mains pressure boosting system increases the pressure and flow of water from the incoming mains supply into a property. It typically combines a pump and a storage or expansion tank, drawing water from the mains and delivering it to taps, showers and appliances at a stronger, more consistent pressure. They are used where the incoming mains is too weak to serve modern outlets reliably.
When do I need a mains booster pump?
You normally need a mains booster if static mains pressure is below 1.5 to 2 bar, if showers run weakly when other taps are open, or if combi boilers struggle to deliver hot water. Anglian Pumping recommends checking static pressure at the stop tap before specifying a system, then choosing a model rated for the number of bathrooms and outlets in the property.
What size mains booster do I need for my home?
Sizing depends on the number of bathrooms, the type of fittings and the static mains pressure. As a guide, a 1 to 2 bathroom property with combi boiler or single shower often needs 1.6 to 3 bar boost. A 2 to 3 bathroom property typically needs 3 to 4.5 bar with an integral break tank. Larger homes need a tank-and-pump system such as the DAB Esybox with Esytank or a Powertank set.
What is a water booster pump?
A water booster pump increases the pressure of an existing water supply to give stronger flow at taps, showers and appliances. It can be a small inline pump fitted to the incoming mains, or a larger pump and tank set that draws from a break tank to feed the whole house. Boosters do not create water – they raise the pressure of the water already coming in.
What is the difference between an inline booster and a tank-and-pump booster?
An inline booster connects straight onto the incoming mains and is limited to 12 litres per minute under UK water regulations – examples include the Salamander HomeBoost and WaterBoost WB-Compact. A tank-and-pump booster, such as the Grundfos Home Booster or DAB Esybox with Esytank, draws from a break tank and can deliver much higher flow rates for larger homes with multiple bathrooms.
What is a variable speed booster pump?
A variable speed booster uses an inverter to adjust pump speed in real time to match demand. It maintains constant pressure as outlets open and close, runs more quietly than a fixed-speed pump and typically saves up to 50 per cent of the energy a fixed-speed equivalent would use. The DAB Esybox, DAB Esybox Mini 3 and Grundfos Scala2 are common variable speed examples.