Automatic irrigation system purging

Apparatus for automatically purging an irrigation system having an irrigation controller controlling water flow into a plurality of irrigation zones, the apparatus comprising:

• a low-pressure switch for determining when pressure within the irrigation system passes a low-pressure threshold;
• a high-pressure switch for determining when pressure within the irrigation system passes a high-pressure threshold;
• a source of compressed air;
• and
• a purge controller including circuitry constructed and arranged to determine pressure within the irrigation system by monitoring the low-pressure switch and the high-pressure switch, to designate irrigation zones, and to apply compressed air to designated irrigation zones to blow water out of the designated irrigation zones based upon the pressure within the irrigation system.

A method of automatically purging an irrigation system having a plurality of irrigation zones, the method comprising the steps of:

• (a) removing water pressure to the system;
• (b) designating an irrigation zone to blow-out;
• (c) blowing water out of the designated zone using pressurized air;
• (d) tracking pressure within the irrigation system as the pressure transitions from a high pressure state to a low pressure state;
• (e) measuring a current pressure transition time;
• (f) comparing the current pressure transition time to a Pressure Transition Time Value for the designated zone;
• (g) flagging the designated zone as Purged when the current pressure transition time is within a designated margin of the Pressure Transition Time Value;
• (h) repeating steps (b) through (g), designating other zones, until all desired zones not already flagged as Purged are blown-out;
• (i) repeating steps (b) through (h) until all desired zones are flagged as Purged or a maximum number of cycles is reached.