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How To Tap Into The Main Water Line

Sprinkler System And Irrigation Basics

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To supply a new sprinkler system, you'll have to tap into your existing cold-water supply system. If your plan calls for cutting existing pipes, you may prefer to hire a plumber. If you do decided to tackle it yourself, be sure to turn off the water supply before you begin any work.


In mild climates, you may tap into an outdoor faucet. In cold-winter climates, or if you don't have adequate water flow at the faucet, you can cut into your main supply line.

Cutting in at an Existing Faucet

Connecting into an existing faucet

Often the easiest course of action is to make the connection at the pipe serving the faucet. With this method, you avoid cutting pipe. Turn off the house water supply and drain the faucet, then remove the faucet and install a brass or galvanized tee. Match the outlet sizes to the faucet pipe and the irrigation pipe you plan to use. Reattach the faucet; then install a nipple (a short length of pipe threaded at each end) in the stem of the tee fitting and connect a shutoff valve to that.

Cutting in at the Service Line

Connecting into the service line

To attach to your main supply line before it enters the house, first shut off the water before the point where you will be cutting. For an above ground connection, remove a short section of pipe in the supply line, leaving just enough of a gap to slide on a slip tee. Install a nipple in the stem of the tee and attached a shutoff valve to it.


Whenever you attach to a potable water system (like your indoor plumbing), always install a backflow preventer to prevent used water from flowing back into the water supply. If you are using antisiphon control valves, a preventer is built into each valve. For a single-circuit system that runs directly off the hose bibb, you can screw a vacuum breaker onto the end of the faucet. Inline valves need a pressure vacuum breaker at the start of the system, as long as it is located higher than the highest sprinkler head. Otherwise, you'll need to install a reduced-pressure (RP) principle backflow preventer on the main line before the valves at a point at least 12 inches above ground.

Reduced Pressure Principle Backflow Preventer

Vacuum Breaker

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