Master Valves

A master valve is a remote-controlled valve (RCV) installed just after the point of connection (POC) and is wired to the controller as a master valve. The purpose of the master valve is to shut off the water to the irrigation system when none of the zone valves are opening. A master valve working with a flow sensor can serve as a water conservation method, and should have the controller programmed to shut off the master valve only in the event of a leak.

Any electric solenoid valve can serve as a master valve, with a pressure rating of at least twice that of your expected water pressure. If the master valve is installed without, or before, a filter system, you should also install a “contamination-proof” or “dirty water” valve, which has a small built-in filter.

Master valves are typically installed after the backflow device, but location is not especially critical.

Advantages

Master valves are advantageous because they minimize water loss or damage when no valves are operating. They are best connected with a flow sensor to minimize damage when valves are either on or off, and they can detect a leak or broken condition.

Disadvantages

The problem with master valves is that, without a working flow sensor, you won’t know whether you have a broken condition if, for example, the system only operates at night. In this case, a leak could go unreported. In the event of a minor leak, which could allow air in the mainline as water leaks out, water hammer can occur when the master valve turns back on and fills the mainline with water at a high velocity. Also, a master valve can lead to premature failure of both PVC and PE pipe due to stretching and contracting of the pipe each time the system is pressurized and then depressurized – especially in high-pressure systems.