When using 80mm Round Downpipe with Hi-Cap and Niagara Systems, fascia brackets should be spaced at a maximum of 800mm intervals. Our reputation for excellence in product quality and. pipe. If additional lengths of downpipe are required, join using a socket and pipepliances in times of drought when the Rainwater tank is empty. The system uses a level sensor inside the tank to open a solenoid val n air gap where the mains water flows into the rainwater tank. The air gap in this system is an anti-splash tundish and ove flow incorporated into one; the. Geberit HDPE offers a full range for all types of drainage, from building drainage to trade effluent.