151 Outdoor Drain Unblocker is specially formulated to unblock drains in only 30 minutes. It is a simple and effective way to unblock outdoor drains, and it's recommended to use 151 Outdoor Drain Unblocker regularly throughout the year to prevent blockages. This fast acting cleaner works to dissolve fat deposits, hair and much more, unblocking the drain and deodorising at the same time. To clear blocked drains, simply pour the contents down the drain, leave to act for 30 minutes, and then flush through with hot water.