Rain Tank Complete Garden Rainwater Harvesting Systems! These rain tanks are the ideal way of creating a complete garden rainwater harvesting system. By combining the wall tanks, Filter Collector, Automatic Garden Steel Pump, Pump to Tank Connector, rainwater level Sight Gauge, & Tank to Tank Connectors. Chosen by irrigation professionals & homeowners alike. Each wall tank system consists of: Wall Tank (s) dependent on system size (800 litre/tank). Tank to Tank Connector (s) to connect all tanks together. Filter Collector, the class leader filter diverter for UK downpipes. Tank Water Level Gauge. Garden Steel Pump with multi-hosetail outlet & carry handle. Tank to Pump Connection Kit.