18 liter solar-wave gws expansion vessel for swb-18lx solar system18 LITER EXPANSION TANK ATT. 3 4 SOLAR WAVE The SolarWave SWB 18LX tank is part of the extensive Global Water Solution product range that offers a complete line of expansion vessels ideal for various applications, including closed loop solar systems, solar thermal expansion hot water. SolarWave expansion vessels are designed to control the expansion and contraction of heat transfer fluids in solar heating systems to keep the entire system efficient