WaterBoost ATX Whole-House Mains Pressure Booster
WaterBoost ATX-250H 4.5 bar Horizontal Whole-House Mains Pressure Booster
- Established 1975
- Trusted by thousands of customers
The WaterBoost ATX-250H 4.5 is the mid-range high-pressure horizontal model in the ATX integrated accumulator booster range, built for lofts, eaves, under-bath voids and low cupboards. It connects directly to the incoming cold water mains, combining a 250-litre sealed horizontal accumulator vessel with the WB-Compact 4.5 variable speed pump mounted beside or in front of it — charging the vessel up to 4.5 bar and boosting both pressure and flow throughout the property the moment a tap or shower is opened. No break tank, no overflow arrangement, just two water connections required.
The system delivers a peak burst flow of up to 80 l/min and up to 24.5 l/min at up to 4.5 bar for up to 11 minutes — before settling to a continuous boosted flow of 12 l/min at 3.0 bar until the vessel recharges. The 250-litre vessel provides 150 litres of useable working capacity. Variable speed inverter technology means the pump only generates the pressure your mains can’t already deliver, keeping running costs to a genuine minimum. Operation is measured at a quiet 40 dB(A), and the pump sits on a WaterBoost QuietPad anti-vibration base so nothing transmits through joists or floorboards. WiFi via the DAB H2D app enables remote monitoring and control, with a Power Shower mode for when you want everything the system has. A mains bypass fits in seconds using 2 clips if the unit ever requires attention.
WRAS approved product — continuous flow stays within the water authority limit of 12 l/min. Fully sealed system — zero air contact with stored water, no hygiene management required. Completely maintenance free. Suited to 2-4 bed homes upwards with two bathrooms, rain heads, body jets, top-floor bathrooms or an unvented cylinder that wants more than 3 bar can give. 5-year tank warranty, 3-year pump warranty. If 3.2 bar is enough, see the standard ATX-250H; step up to the ATX-300H 4.5 for larger homes, or down to the ATX-200H 4.5 for a single bathroom.
3yr pump
Up to 4.5 bar
WiFi · H2D app
WRAS approved
Zero maintenance
Sealed — no air contact
Variable speed
250L · 150L useable
No overflow
Dry run protection
QuietPad fitted
Bypass fits with 2 clips
More about this product
3yr pump
What is the ATX-200H 4.5?
The WaterBoost ATX-200H 4.5 is the high-pressure horizontal model in the ATX integrated accumulator booster range. It connects directly to your incoming cold water mains supply, combining a 200-litre sealed accumulator vessel mounted on its side with the WB-Compact 4.5 variable speed pump — the most powerful direct mains booster in the WaterBoost range — beside or in front of it. The pump charges the vessel up to 4.5 bar; open a tap or shower and the system boosts both pressure and flow throughout the property instantly. At 532 mm high it goes into the loft, the eaves, the void under a bath or a low cupboard. No break tank, no overflow arrangement, and just two water connections required.
The 200-litre vessel provides 120 litres of useable working capacity, enabling the ATX-200H 4.5 to sustain a boosted flow of 22 l/min at up to 4.5 bar for up to 11 minutes — suited to a single bathroom with a rain head or body jets, or one shower alongside additional outlets — before the vessel recharges automatically. Peak burst flow at the moment of demand is up to 80 l/min. Once the stored volume is exhausted, the system continues to deliver a boosted 12 l/min at 3.0 bar until demand ceases and the vessel refills.
Where it fits — the spaces an upright booster can’t use
An upright 200-litre accumulator stands over 1.3 m tall. Plenty of homes have the floor space for a booster but not the height — or have the height only in places nobody wants a pump. The ATX-200H 4.5 is built for those homes: 532 mm high (plus feet), 1,326 mm long, and it goes where an upright can’t. The pump is mounted on a WaterBoost QuietPad anti-vibration base as standard, so its hum doesn’t travel through joists into the rooms below.
Why 4.5 bar?
Most homes are happy at 3 bar. Some aren’t: a rain head or body jets that need real pressure to perform, a top-floor bathroom in a three-storey house where every metre of rise costs a tenth of a bar, or an unvented cylinder whose inlet group wants more than the mains can give. The standard ATX-200H tops out at 3.2 bar. The ATX-200H 4.5 charges the same vessel up to 4.5 — and because a loft is usually the top of the house, it’s the version that makes most sense up there.
Energy efficiency — only boosts what your mains can’t deliver
The WB-Compact 4.5’s variable speed inverter continuously measures incoming mains pressure and adjusts its output to produce only the shortfall. If your mains delivers 1.5 bar and your target is 4.5 bar, the pump generates 3 bar. If your mains delivers 2.5 bar, the pump generates 2 bar. No wasted energy, no fixed worst-case output.
This is a fundamental advantage over water storage tank boosters, which run at the same full output regardless of what the mains already provides. Running costs with the ATX-200H 4.5 reflect exactly what is needed — nothing more.
Sealed system — zero air contact with your water
The ATX operates as a fully closed pressurised circuit from mains inlet to outlet. The accumulator vessel is sealed and pressurised — there is no open water surface, no air gap, and no point at which atmospheric air contacts the stored water. This is a fundamentally different design to an open storage tank system, with important advantages for water quality and safety — and it matters more in a loft, where an open tank collects dust and heat.
The WB-Compact 4.5 is WRAS approved for direct mains connection, and the vessel is WRAS approved for potable water. The complete system carries WRAS approval.
✗ Open water surface — air, dust and debris can enter
✗ Requires periodic tank cleaning and inspection
✗ Overflow pipe required — ongoing hygiene risk point
✗ Water sits static — Legionella risk management may apply
✓ Fully sealed vessel — zero air contact with water
✓ No open surface, no dust or debris ingress
✓ No overflow pipe required
✓ WRAS approved product
WRAS approved product. Confirms the system meets UK Water Supply (Water Fittings) Regulations, is safe for use with potable water, and will not cause contamination of the mains supply. Continuous flow is capped at 12 l/min in line with water authority requirements.
Zero maintenance — fit it and forget it
The ATX is a completely maintenance-free system. There are no consumable parts, no filters to replace, no annual service requirements and no engineer visits needed. The sealed design removes the hygiene maintenance obligations of open storage, and the pump’s automatic pressure sensing, dry run protection and anti-seize exercise function mean the system manages its own long-term health automatically — which is exactly what you want from something in a loft.
What happens after installation
| Day 1 — Installation | Two water connections. Unit installed and commissioned. That’s it. |
| Year 1 — Nothing | No service visit. No filter change. No tank clean. System self-monitors via the H2D app. |
| Year 2 — Nothing | Anti-seize function runs automatically during low-demand periods. No action required. |
| Years 3 & 4 — Nothing | Pump warranty active. Dry run protection monitoring. Still no maintenance. |
| Year 5 — Warranty | 5-year tank warranty still in force. System continues to operate without scheduled maintenance. |
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30-second pump swap — unique dock system
If a pump replacement is ever needed, the ATX dock system allows the pump unit to be removed and replaced in under 30 seconds using two clips — no draining, no tools, no plumber required. The built-in full-bore bypass keeps the property on mains supply throughout. In a loft, that’s the difference between a five-minute job and an afternoon.
How it works — two-phase operation
The ATX-200H 4.5 stores a ready supply of pressurised water in its 200-litre accumulator vessel, charged up to 4.5 bar. When demand occurs, it delivers instant high-flow boosted water immediately, then continues at a sustained flow once the stored volume is used, before recharging automatically.
Phase 1 — Stored volume
Instant high-flow boost
22 l/min
at up to 4.5 bar — for up to 11 minutes
Delivered directly from the accumulator charged up to 4.5 bar. Suited to a single bathroom with a rain head, or one shower and additional outlets in simultaneous use.
Phase 2 — Continuous mains
Sustained boosted flow
12 l/min
at 3.0 bar — continuous
Once stored volume is exhausted, the WB-Compact 4.5 continues boosting direct from the mains at its real-world output. Vessel recharges up to 4.5 bar automatically when demand stops.
How it compares — WaterBoost ATX-200H 4.5 vs Stuart Turner Stormboost 200
Both systems target direct mains boosting for similar property sizes. The Stormboost is upright only.
| Feature | WaterBoost ATX-200H 4.5 | Stuart Turner Stormboost 200 |
|---|---|---|
| Orientation | Horizontal — lofts, eaves, under-bath ✔ | Upright only |
| Max pressure | Up to 4.5 bar ✔ | 3 bar |
| Anti-vibration mounting | QuietPad fitted as standard ✔ | Not supplied |
| Pump type | Variable speed inverter ✔ | Fixed speed induction motor |
| Energy efficiency | Only boosts the shortfall ✔ | Fixed output regardless of mains |
| Sealed system | Fully sealed — zero air contact | Fully sealed — zero air contact |
| Noise | 40 dB(A) rated ✔ | Quiet — no dB rating stated |
| WiFi / App | DAB H2D app ✔ | No |
| Overflow required | No ✔ | No |
| Maintenance bypass | 2-clip fit — 30 seconds ✔ | Integral bypass |
| Maintenance required | Zero — maintenance free ✔ | Periodic maintenance advised |
| Warranty | 5yr tank · 3yr pump ✔ | 3 years total |
Technical specifications
| Brand / Model | WaterBoost — ATX-200H 4.5 (Horizontal) |
| System type | Integrated accumulator booster — direct mains, horizontal vessel, up to 4.5 bar |
| Pump | WaterBoost WB-Compact 4.5 (ACM series), variable speed inverter |
| Water connections | 2 — inlet & outlet, 1″ BSP |
| Accumulator capacity | 200 litres total · 120 litres useable working capacity |
| Max pressure | Up to 4.5 bar |
| Peak burst flow | Up to 80 l/min |
| Sustained boosted flow | 22 l/min at up to 4.5 bar for up to 11 minutes |
| Continuous flow (post-discharge) | 12 l/min at 3.0 bar |
| Noise level | 40 dB(A) |
| Anti-vibration | WaterBoost QuietPad fitted under the pump as standard |
| Vessel dimensions | 1,326 mm long × 532 mm diameter · 532 mm high plus feet · pump beside (1,599 mm total) or in front (778 mm total depth) · pump 439 × 263 × 236 mm |
| Weight (empty / filled) | ~51 kg / ~251 kg — confirm joist loading for loft installs |
| WiFi / connectivity | Yes — DAB H2D app |
| Sealed system | Yes — no overflow required |
| Air contact with water | None — fully sealed pressurised vessel |
| WRAS approved | Yes — pump approved for direct mains connection; vessel approved for potable water |
| Dry run protection | Yes — built in |
| Anti-seize exercise function | Yes — automatic |
| Maintenance bypass | Full-bore bypass, fitted in under 30 seconds using 2 clips |
| Maintenance required | None — completely maintenance free |
| Suited to | 2-4 bed homes · rain heads and body jets · top-floor bathrooms · combi-boiler properties · unvented cylinder systems · loft, eaves and under-floor installs |
| Warranty | 5-year tank · 3-year pump |
Flow rates are dependent on incoming mains supply. Continuous flow of 12 l/min at 3.0 bar applies after stored volume is exhausted.
Frequently asked questions
Horizontal or upright — which do I need?
Go by the space. The ATX-200H 4.5 is 532 mm high and 1,326 mm long — for lofts, eaves, under a bath or a low cupboard. The upright ATX-200 4.5 is 1,326 mm high on a 532 mm footprint — for a plant room, garage or utility with the headroom. Capacity, pressure, performance and warranty are the same; only the shape differs.
Can I put it in the loft?
Yes — that’s what it’s for, and at 4.5 bar it’s the right version for a top-floor bathroom. Two checks first: the 532 mm vessel diameter has to fit through the hatch, and the joists have to carry the filled weight. Spread the load across joists on a board, and keep the pump end accessible for the bypass clips. The QuietPad under the pump stops vibration reaching the ceiling below.
Is 4.5 bar too much for my appliances?
For most, no. Combis and unvented cylinders are typically rated to 4.5–6 bar and have their own pressure reducing valve set at 3, so they see what they’re designed for. Anything downstream rated below 4.5 bar needs its own PRV — check the label on older appliances. If you’d rather not, the standard ATX-200H runs at 3.2 bar.
Why does the continuous flow drop to 3.0 bar?
The 4.5 bar is what the vessel is charged up to, and what you get while stored water is discharging — up to 11 minutes of full use. Once the vessel is empty the pump is boosting the mains alone, and its real-world output is 12 l/min at 3.0 bar. That’s still a full boost, and the vessel recharges up to 4.5 as soon as demand stops.
Is the ATX-200H 4.5 the right size for my property?
It’s suited to 2-4 bed homes where one bathroom is in regular use and pressure — not just flow — is the complaint. For two bathrooms in regular simultaneous use, consider the ATX-250H 4.5 or ATX-300H 4.5.
Why is the ATX more energy efficient than a storage tank booster?
A storage tank booster always runs at full output regardless of mains conditions. The ATX’s variable speed pump measures incoming pressure and produces only the shortfall — if your mains provides 2.5 bar, the pump adds 2. Over a year this makes a meaningful difference to running costs, particularly where mains pressure varies by time of day or season.
Why is a sealed system better for water hygiene?
An open break tank has an exposed water surface where airborne dust, debris and microorganisms can enter, and requires regular cleaning and inspection. The ATX has no open surface — the accumulator vessel is sealed and pressurised, operating as a closed circuit throughout with no point at which air contacts the stored water. In a loft that matters twice over.
What maintenance does the ATX need?
None. There are no service intervals, no consumable parts, no filter changes and no annual engineer visits required. The anti-seize exercise function runs the pump automatically during inactivity. Dry run protection safeguards the pump if the mains supply is interrupted. The H2D app allows remote monitoring. The system looks after itself.
What happens if the pump needs replacing?
The unique ATX dock system allows the WB-Compact 4.5 to be removed and replaced in under 30 seconds using two clips — no draining, no tools, no plumber required. The full-bore bypass keeps your property on water throughout.
Is the ATX suitable for a combi-boiler or unvented cylinder property?
Yes. The ATX is designed for direct mains connection and is well suited to both combi-boiler homes and properties with unvented hot water cylinders — the 4.5 bar version particularly where the cylinder is on an upper floor. Installation should comply with Water Regulations and be carried out by a qualified plumber.
Are other sizes available?
Yes. The horizontal 4.5 bar range comes in three sizes — the ATX-200H 4.5, the ATX-250H 4.5 for two bathrooms in regular simultaneous use, and the ATX-300H 4.5 for larger homes with longer peak demand. Upright, the 4.5 bar range runs from the ATX-200 4.5 to the ATX-450 4.5.
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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 ATX-250H 4.5 bar Horizontal Whole-House Mains Pressure Booster. 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.