GWS ThermoWave Potable Hot Water Expansion Tanks
GWS ThermoWave Vertical TWB-60LV
- Established 1975
- Trusted by thousands of customers
The GWS ThermoWave™ TWB-60LV is a 60 litre vertical expansion vessel for potable hot water. It is the only vertical model in the ThermoWave range. It stands on its own base with a 389 mm footprint, so it fits plant rooms where floor space is tighter than headroom. As stored water heats, it expands. The vessel absorbs that extra volume, so the relief valve doesn’t discharge hot water to drain.
The water only touches a virgin polypropylene liner and high-grade butyl diaphragm, never the steel shell. It has a patented stainless steel water connection and an O-ring sealed air valve, and needs no maintenance. Connection is ¾″ BSPT. It comes pre-charged to 1.9 bar and is rated to 10 bar and 90 °C.
Vertical, floor-standing
Butyl diaphragm
Small footprint
¾″ BSPT
Model TWB-60LV
More about this product
Product overview
The GWS ThermoWave™ TWB-60LV is a 60 litre (15.9 US gal) vertical expansion vessel for potable hot water. When a water heater warms its stored water, the water expands. Without an expansion vessel, the relief valve vents the extra water to drain. That wastes water and the energy used to heat it, and every cycle wears the valve.
The TWB-60LV takes up that expansion volume and returns it as water is drawn off. It’s the only vertical model in the ThermoWave range and holds the same 60 litres as the horizontal TWB-60LH. It stands upright on a rigid base: 619 mm tall on a 389 mm diameter footprint, around 140 mm narrower than the horizontal version is long. Inside, the water is held in a virgin polypropylene liner sealed by a high-grade butyl diaphragm, so it never touches the steel shell.
Key features
Typical applications
Technical specifications
| Brand / Series | GWS — ThermoWave™ |
| Model | TWB-60LV |
| Type | Vertical, freestanding on base |
| Nominal volume | 60 L / 15.9 US gal |
| Connection | ¾″ BSPT, stainless steel |
| Factory pre-charge | 1.9 bar / 28 psi |
| Max operating pressure | 10 bar / 150 psi |
| Operating temperature | −10 °C to +90 °C |
| Liner | Virgin polypropylene |
| Diaphragm | High-grade butyl |
| Air valve | O-ring sealed |
| Finish | Two-part polyurethane, primed |
| Height (A) | 619 mm |
| Diameter (B) | 389 mm |
| Connection height (C) | 63 mm |
| Gross weight | 11.6 kg |
Frequently asked questions
Vertical or horizontal — which should I choose?
Both hold 60 litres. The TWB-60LV stands 619 mm tall on a 389 mm footprint and suits tight floor space. The horizontal TWB-60LH is 408 mm high and 527 mm long, so it’s the one to use where headroom is limited.
Where does it fit?
On the cold feed to the water heater, between the heater and any non-return or pressure-reducing valve. Stand it on its base on a level floor.
What should the pre-charge be set to?
It arrives at 1.9 bar. Check it with the vessel empty and set it to your incoming cold supply pressure before filling.
Which size do I need?
It depends on the volume of stored hot water and your supply pressure. At 60 litres this is the largest ThermoWave. Check the water heater manufacturer’s recommendation, or ask our team if your system needs more.
Can I use it on central heating?
It’s designed for potable hot water. For sealed central heating systems, use the GWS HeatWave™ range.
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 GWS ThermoWave Vertical TWB-60LV. 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.