Isolation tap and check valves are essential for irrigation You will need a registered plumber to do this part. Every system should have a tap that can turn off the reticulation system in the case of an emergency. This is called an ‘isolation tap’. Attached to this tap is a ‘Dual Check Valve’. Basically it stops water going backwards into the mains drinking supply. Would you like to drink water from someone’s retic system? Didn’t think so. These are very important. It’s sad to say but many syste