GWS HeatWave Hydronic Expansion Tanks
GWS HeatWave HWB-130LV heating expansion tank
- Established 1975
- Trusted by thousands of customers
The GWS HeatWave™ HWB-130LV is a 130 litre vertical expansion vessel for closed-loop heating systems. As the water heats and expands, the vessel’s air-charged chamber takes up the extra volume, holding system pressure steady and keeping it off the relief valve.
High-grade butyl diaphragm, chromed steel connection and brass O-ring sealed air valve, with a two-part polyurethane finish over epoxy primer. It stands on its own rigid base, so no wall bracket is needed. 1″ BSPP, factory pre-charged to 1.5 bar, rated to 6 bar and 99 °C.
Butyl diaphragm
Freestanding vertical
1″ BSPP
Glycol compatible
Model HWB-130LV
More about this product
Product overview
The GWS HeatWave™ HWB-130LV is a 130 litre (34.3 US gal) vertical expansion vessel for sealed, closed-loop heating systems. Water expands as it heats. Without somewhere to go, that extra volume pushes system pressure up until the relief valve lifts. The HeatWave’s air-charged chamber absorbs it instead, keeping pressure steady through every heat-up and cool-down.
HeatWave™ tanks are built to the same standards as GWS PressureWave™ and Challenger™ vessels, with a high-grade butyl diaphragm, chromed steel water connection and brass air valve with O-ring sealed cap. The vertical models stand on a rigid base, so the HWB-130LV is floor-standing with no wall bracket needed.
Key features
Typical applications
Technical specifications
| Brand / Series | GWS — HeatWave™ |
| Model | HWB-130LV |
| Type | Vertical, freestanding on integral base |
| Nominal volume | 130 L / 34.3 US gal |
| Connection | 1″ BSPP, chromed steel |
| Factory pre-charge | 1.5 bar / 22 psi |
| Max operating pressure | 6 bar / 87 psi |
| Operating temperature | −10 °C (avoid freezing) to +99 °C |
| Diaphragm | High-grade butyl |
| Air valve | Brass, O-ring sealed cap |
| Finish | Two-part polyurethane over epoxy primer, grey |
| Height (A) | 958 mm |
| Diameter (B) | 430 mm |
| Gross weight | 18.9 kg |
| Suitable for | Closed-loop, non-potable hydronic heating only |
Frequently asked questions
What does a heating expansion vessel do?
Water expands as a heating system warms up. The vessel’s air-charged chamber takes up that extra volume, so system pressure stays steady and the relief valve doesn’t lift every time the heating comes on.
Can I use it on a drinking-water or booster system?
No. HeatWave™ vessels are for closed-loop, non-potable heating only. For drinking water or pump boosting, use a potable vessel such as the GWS PressureWave™ PWB-130LV.
What should the pre-charge be set to?
It arrives at 1.5 bar. Check it with the vessel empty and set it to your system’s cold fill pressure before filling.
Can I use antifreeze?
Yes, propylene glycol at concentrations up to 50%. GWS advise avoiding ethylene glycol.
Does it need a wall bracket?
No. The HWB-130LV stands on its own rigid base. Place it on a level floor that can take its filled weight.
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Data Sheet 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 GWS HeatWave HWB-130LV heating expansion tank. 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.