If you have a good idea how much watering your plants need but don’t want to or can’t be there, the water timer’s for you. Though no bigger than a coffee can, some of these gadgets contain a small computer that you can program for watering time and duration. Others have a clever intermittent feature that delivers the water in on-off cycles (for instance, five minutes on followed by a ten-minute rest) over a period of time (say, three hours) before shutting off automatically. This allows the soil to efficiently absorb the water with far less runoff and evaporation.
The fancy battery-operated types with all the settings are handy if you need all these features, but if you’re after simplicity and dependability, you can’t beat the spring-operated ones. One end of the timer attaches to the faucet, the other to the hose end — you have no batteries, no wires to worry about. Some timers are more elaborate (and expensive) than others, so have a clear idea of your needs as well as your technological savvy when you go shopping. You can find water timers wherever gardening supplies are sold, as well as at specialty greenhouse supply companies.
Water timers are most often used with professional installed sprinkler systems