GWS ThermoWave Potable Hot Water Expansion Tanks
The GWS ThermoWave™ range are expansion vessels built for potable hot water systems. Water expands as it heats, and without an expansion vessel the relief valve dumps that hot water to drain, so it has to be refilled and heated again. A ThermoWave absorbs the expansion instead, holding pressure steady and saving the water and energy that would be vented.
The water only ever touches a virgin polypropylene liner and a high-grade butyl diaphragm, never the steel shell, so drinking water stays clean. Each vessel has a patented stainless steel water connection, a leak-free O-ring sealed air valve and a two-part polyurethane primed finish, and is maintenance-free.
Thirteen sizes from 2 to 60 litres. Inline models mount directly on the pipework; horizontal models sit on replaceable tank feet; the 60 litre vertical stands on its own base. Every model is ¾″ BSPT, rated to 10 bar and 90 °C, and factory pre-charged to 1.9 bar.
| Model | Type | Volume | Size (A × B) |
|---|---|---|---|
| TWB-2LX | Inline | 2 L | 206 × 126 mm |
| TWB-4LX | Inline | 4 L | 258 × 162 mm |
| TWB-8LX | Inline | 8 L | 310 × 202 mm |
| TWB-12LX | Inline | 12 L | 364 × 230 mm |
| TWB-18LX | Inline | 18 L | 364 × 279 mm |
| TWB-24LX | Inline | 24 L | 444 × 290 mm |
| TWB-35LX | Inline | 35 L | 478 × 318 mm |
| TWB-12LH | Horizontal | 12 L | 364 × 260 mm |
| TWB-20LH | Horizontal | 20 L | 444 × 277 mm |
| TWB-24LH | Horizontal | 24 L | 444 × 306 mm |
| TWB-35LH | Horizontal | 35 L | 478 × 338 mm |
| TWB-60LH | Horizontal | 60 L | 527 × 408 mm |
| TWB-60LV | Vertical | 60 L | 619 × 389 mm |
A = height (length on horizontal models), B = diameter (height on horizontal models). All models ¾″ BSPT. For sealed central heating, use the GWS HeatWave™ range instead.
13 products
The GWS ThermoWave™ TWB-2LX is a compact 2 litre inline expansion vessel for potable hot water. As stored water heats, it expands. The vessel absorbs…
The GWS ThermoWave™ TWB-4LX is a 4 litre inline expansion vessel for potable hot water. As stored water heats it expands; the vessel absorbs that…
The GWS ThermoWave™ TWB-8LX is an 8 litre inline expansion vessel for potable hot water. As stored water heats, it expands. The vessel absorbs that…
The GWS ThermoWave™ TWB-12LX is a 12 litre inline expansion vessel for potable hot water. Stored water expands as it heats. The vessel absorbs that…
The GWS ThermoWave™ TWB-18LX is an 18 litre inline expansion vessel for potable hot water. Stored water expands as it heats. The vessel absorbs that…
The GWS ThermoWave™ TWB-24LX is a 24 litre inline expansion vessel for potable hot water. Stored water expands as it heats. The vessel takes up…
The GWS ThermoWave™ TWB-35LX is a 35 litre inline expansion vessel for potable hot water, and the largest inline model in the ThermoWave range. Stored…
The GWS ThermoWave™ TWB-12LH is a 12 litre horizontal expansion vessel for potable hot water. It lies on its side on its own feet, standing…
The GWS ThermoWave™ TWB-20LH is a 20 litre horizontal expansion vessel for potable hot water. It lies on its side on its own feet and…
The GWS ThermoWave™ TWB-24LH is a 24 litre horizontal expansion vessel for potable hot water. It lies on its side on its own feet and…
The GWS ThermoWave™ TWB-35LH is a 35 litre horizontal expansion vessel for potable hot water. It lies on its side on its own feet and…
The GWS ThermoWave™ TWB-60LH is a 60 litre horizontal expansion vessel for potable hot water, the largest horizontal model in the range. It lies on…
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.…
Frequently Asked Questions
Quick answers to common questions about the GWS ThermoWave Potable Hot Water Expansion Tanks. 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.