Accumulator Vessels
300 litre accumulator vertical GWS GCB-300LV
- Established 1975
- Trusted by thousands of customers
The GWS GCB-300LV is a 300-litre WRAS-approved vertical accumulator vessel for mains-connected water systems. Accumulators store mains water under pressure — so when you open a tap or shower, you draw instantly from the vessel at full mains pressure rather than waiting for the mains to respond. The result is a noticeably stronger, more consistent flow from every outlet, even during peak demand.
The GCB-300LV operates on a 60% usable volume ratio — delivering approximately 180 litres of high-pressure water before returning to normal mains flow. Diaphragm design, patented stainless steel water connection, virgin polypropylene liner, 10 bar max working pressure, factory pre-charged to 1.4 bar. Maintenance free and WRAS approved. Suitable for 2–3 bedroom homes.
Requires a minimum 2 bar static mains pressure to operate effectively. If your static pressure is below 2 bar, add the WaterBoost ACF1 accumulator booster pump to charge the vessel to the required working pressure.
Maintenance free
Diaphragm design
2–3 bedroom homes
ACF1 pump if <2 bar
More about this product
An accumulator is a large pressurised vessel that connects directly to your mains supply. It stores mains water under pressure — so when you open a tap, shower, or appliance, water discharges immediately from the vessel at full mains pressure rather than drawing directly from the street main. The effect is noticeably stronger, more consistent flow throughout the home, even when multiple outlets are used simultaneously or when street pressure drops during peak demand periods.
Unlike a WaterBoost tank-and-pump system, an accumulator has no pump and no moving parts — it works entirely on mains pressure. This makes it maintenance free and silent. It is the right solution when your mains pressure is adequate (above 2 bar static) but flow is poor or inconsistent. If static mains pressure is below 2 bar, a boost pump should be added to charge the accumulator to a higher working pressure.
The GWS GCB-300LV is a 300-litre WRAS-approved vertical accumulator from GWS — built for domestic cold water installations with a patented stainless steel water connection, virgin polypropylene liner, diaphragm design, and a 10 bar maximum working pressure.
GWS recommends the following vessel sizes based on property type. All figures use the 60% usable volume rule.
How much does it cost?
What is the difference between an accumulator and a WaterBoost tank-and-pump system?
What mains pressure do I need for an accumulator to work?
How do I check my static mains pressure?
What size accumulator do I need?
Does the accumulator need any ongoing maintenance?
Uses –
- 1 to 2 bedroom house – 60 litre,100 litre or 200 litre
- 2 to 3 bedroom thouse – 200 litre, 250 litre or 300 litre
- 3 bedrooms and above – 300 litre or 450 litre
Remember GWS accumulators operate on a 60% volume to use ratio meaning a 300 litre vessel gives 180 litres of powerful water before returning to mains flow.
To find your vessel usage times vessel size by 0.6.
An average shower/bath runs at 10-12 litres/min. So 300 litre GWS x 0.6 = 180 litres. This will operate 2 showers at 12 litres/min for 180 / (12 litres/min x 2 ) = 7.5 minutes.
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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 300 litre accumulator vertical GWS GCB-300LV. 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 the GWS 300 litre vertical accumulator?
The GWS GCB-300LV is a 300 litre WRAS approved vertical accumulator vessel for mains-connected cold water systems. It stores mains water under pressure so when you open a tap or shower, water discharges instantly from the vessel at full mains pressure – delivering stronger, more consistent flow at every outlet. It has no pump, no moving parts and needs no routine maintenance.
What mains pressure does the GWS 300 litre accumulator need to work?
The GCB-300LV needs a minimum 2 bar static mains pressure to operate effectively. If static mains pressure is below 2 bar, pair the accumulator with a WaterBoost ACF1 accumulator charge pump – this charges the vessel to a higher working pressure. Maximum working pressure is 10 bar and the vessel is factory pre-charged to 1.4 bar.
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 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.