The Complete Handbook of Water Timers

Chapter 1: Understanding Water Timers

A water timer is a mechanical or electronic device that opens and closes a valve in a water supply line according to a preset schedule. That is the entirety of its function. It does not pump water, filter water, or change water pressure. It is a switch for water, controlled by time. This simplicity is why the category is so widespread and reliable, and understanding that core function is the key to choosing, installing, and troubleshooting any timer on the market.

To understand a water timer, you must first look at its most critical component: the valve. In almost every modern water timer, this valve is a solenoid valve. A solenoid valve uses an electromagnet to operate a plunger that opens or closes a small pilot orifice. When the solenoid coil is energized, it creates a magnetic field, pulling a metal plunger up. This opens the pilot orifice, which releases pressure from above the main diaphragm. The higher pressure in the inlet water then pushes the diaphragm up, opening the main valve and allowing water to flow. When the current is cut, the plunger falls back, the pilot orifice closes, and pressure builds up above the diaphragm again, forcing it shut against the valve seat. This two-stage system means that a small, low-power solenoid can control a much larger and faster water flow than it could handle directly.

Consider a typical residential lawn irrigation system. The timer is mounted to an outdoor faucet, and it