The Drainback tank or expansion vessel

The solar circuit can be a pressurised circuit requiring an expansion vessel, or a ‘drain back’ circuit with a drain back tank.

The drain back system requires no freeze protection. When the pump is off, the water in the system will flow out of the panel and back into a tank that is situated inside the property where it will not freeze.

In a pressurised system, antifreeze is added into the solar circuit. The anti-freeze never comes into contact with the water you use because the system is a closed loop and the coil in the cylinder is a heat exchange coil where only heat – not anti-freeze, is transferred.