It seems simple enough. In order to have irrigation you need water. In most places, water destined for irrigation MUST be isolated from the water we would normally drink. To accomplish this neat little trick, most places in the country require some form of back-flow prevention. Something on the water supply that keeps the irrigation water (along with fertilizer, weed killers, dog poop, etc) from flowing backwards into the drinking water.
What does this have to do with making sure the water supply is on? Well, in most cases, this back-flow thingee is also what’s used to turn off the water to the irrigation system. Most houses that are served by municipal water systems (a water meter) use a Pressure Vacuum Breaker or PVB for back-flow prevention. Below is a picture of a typical PVB.
Most PVBs look very similar to the ones above. What’s nice about this picture is it shows how to turn the irrigation water off at the PVB. Notice that there are 2 handles on each PVB. One set has yellow tips and one set has blue. These are shut off valves or ball valves that can be used to shut off the water flow. Also notice that both yellow tipped handles and one of the blue tipped handles are turned to line up with the direction of the pipe. These 3 handles are in the ‘ON’ position. The other blue handle (the lower one) is turned so that it is perpendicular to the pipe (crosses it). This handle is in the ‘OFF’ position.
So here’s the situation, your grass looks dry and you wonder if your irrigation is running. You go to the timer and start a zone manually, the timer shows the zone is running but nothing is happening. Somewhere around the house, normally next to the house you will find a PVB like the one shown above. Look to see if someone (the lawn guy, your neighbor, the kids, whomever) turned off (crosses the pipe) one or both of valves (either one or both will shut off the water). If so, turn it back on (in line with the pipe). They are very hard to turn so you will probably need a pair of pliers of a wrench to turn it. When you do, presto, the irrigation should start working.
I know it seems unlikely but I get calls from about 10 homeowners a year who can’t get their systems working because the water was turned off at the PVB and they didn’t know it. Of course this isn’t the only thing that can keep the system from running. I plan to go over lots of other potential problems but the water supply shut off at the PVB is the easiest to check and has the potential for the highest embarrassment factor.