Before laying the traffic areas to the side or backfilling, a leak test must be performed based on DIN EN 1610, 13.3 »Test with water (method »W«)«. In deviation to the provisions contained in the standard, the channel elements must be filled with water at the low point up to the top of the slot and the water level must be kept constant for the whole of the test period. The values in DIN EN 1610, 13.3.4 apply to the maximum quantity of water added.