Where and How to Connect Your Irrigation System to Your Water Supply:
This page provides some specific rules, tips, and techniques for tapping into a house water supply pipe for a new irrigation system. Where and how you tap into the water supply can be critically important, not just for the proper operation of the irrigation system, but also for the preservation of your sanity!
The first thing you need to do is to contact your water provider (assuming you have one) and find out if they have any specific requirements on where to tap irrigation systems into the water supply. Most of the time the only requirement they have will be that the irrigation tap needs to be after the water meter, meaning the water needs to go through the meter to reach your irrigation system (so that you pay for the irrigation water!)
In some places you will be required to install a second water meter for the irrigation water (ie; at the time I am writing this the state of California (USA) is considering a state-wide requirement that all new irrigation systems must have a second, separate water meter that measures only irrigation water. Some local water companies already require separate meters.) If that is the situation the water provider will likely have a very specific place, method, and brand of meter you must use for the irrigation water tap. The location of the tap will depend on what kind of water meter they require, so they will need to help you. They may require that a professional certified by the water provider install the meter.
Typical Irrigation Water Tap Location: If a separate water meter is not required the general rule-of-thumb is that the irrigation tap is installed someplace on the water supply pipe after any water meters and before the house emergency shut-off valve. That allows the irrigation to still work even if you need to shut off the house water for an emergency. A second emergency shut-off valve is installed on the irrigation system water supply after the tap. I like to install a hose outlet on the house water supply pipe before the house emergency shut-off valve. That way it the house water has to be shut-off in an emergency the homeowner will still have a source of water!
Warm Climates: A typical warm climate home has a water supply pipe that goes underground from the water source to the house. Typically this pipe is buried about 18 inches deep. At the house the supply pipe comes up out of the ground, makes a right angle, then goes into the house wall. The emergency shut-off valve for the house is almost always located on this above ground section of pipe where it is convenient to get to it. The normal method of installing a irrigation tap is to cut into this supply pipe anyplace between the water meter (if there is one) and the house emergency shut-off valve. The cut and tap may be made into either the below ground part of the pipe or in the section where the pipe is above ground. Whatever is easiest and most convenient for you.
If the tap is going to be made underground, it may be possible and easier to install a tap by cutting into the water supply pipe and installing a special tee called a “compression tee” (see How to Use Compression Tees & Couplings.)
Cold Climates: In cold winter climates the water supply for the house typically goes from the water supply to the house underground, often buried several feet deep to protect it from frost. It typically enters the house through a basement or crawl space below the house floors. A water meter is often installed on the water supply pipe in the basement or crawl space. The irrigation tap has to be after the water meter (if you have one.) Because the water supply pipe is usually buried very deep, most people install the irrigation tap in the basement or crawl space where it is easier to reach. If you are tapping into a water supply in a basement or under a house you may want to hire a plumber to install the tap if you are not experienced at plumbing work. You don’t want a flooded basement if you mess it up.
If the tap is to go outside the house and underground, it may be possible and easier to install a tap by cutting into the water supply pipe and installing a special tee called a “compression tee” (see How to Use Compression Tees & Couplings.)
Don’t Route Irrigation Water Through the House Pipes!
If at all possible do not tap into a pipe or use a stub-out where the water will need to flow through the house to get to the irrigation system (other than through the basement.) In other words, you do not want the water to go through pipes inside the house walls to get to the irrigation system. I see a lot of homes where the builder has provided an irrigation outlet on the back of the house, with the water running through the house to reach it. Most people who utilize one of these outlets regret it! There are a few reasons for this:
- Flow Restrictions. First, there may be restrictions in the piping as it goes through the house that you can’t see and don’t know about. This includes multiple turns, small size pipe sections, crimps in the tube, and all kinds of things.
- Noise! The second reason is that it is likely that the irrigation will be running at night. Often the irrigation water will make a lot of noise as it moves through the house pipes and it sounds a lot louder during the quiet of night.
- Damage to Pipes. The 3rd reason is the worst one of all, a phenomenon called “scrubbing.” Scrubbing is when excessive water velocity in a pipe causes extreme wear on the inside of the pipe. Water is abrasive and it will eat away the inside of a pipe or tube over time! (Feel free to look up scrubbing on the Internet. Repairing the damaged pipes is a huge industry in some parts of the USA.) Houses with copper pipe and tube are especially vulnerable to scrubbing damage.
- Water Softeners. If you have one (or ever plan to install one) the irrigation water can’t go through it. Chances are any water that goes through the house also is softened if there is a softener. This includes the exchangeable tank softeners that water quality services bring out to your house, chances are they use salt/sodium to soften the water. Even if you use a potassium salt type of softener that is easier on plants, the cost of using soft water for irrigation is going to be enormous.
So I recommend that if you need to get water from one side of the house to the other, that you install a new pipe around the house. If you decide to use an outlet on the side of the house, perform a simple test. If there is a hose on the outlet remove it (the hose will restrict the flow.) Wait until late at night and then open up that faucet all the way. Then go inside and see how loud it sounds inside the house. The noise will likely be even louder when the irrigation system is installed.
I realize sometimes you have no choice but to route the water through the house. If so I suggest you reduce the flow for each valve zone. Lowering the flow reduces the water velocity in the pipes. With a lower velocity, there is much less chance you will have any of these problems occur. Try to keep it under 4 feet/second. (The Pressure Loss Spreadsheets will give you the velocities for various flows and pipes.) You may need to double the number of valves to lower the flow, but it is better than listening to the noise, or worse, having to spend thousands of dollars to replace the pipes in the house walls because they were destroyed by scrubbing!
Its a good idea to install an emergency isolation or “shut-off” valve on the irrigation water pipe as close as possible to the point where you tap into the water supply. That way you can easily and quickly shut-down the irrigation system for emergencies or repairs. In areas where it freezes in winter this valve should be protected from freezing. The standard is to use a ball valve for the isolation valve. Inexpensive “gate valves” have a tendency to fail after just a few uses. This is a good place to spend more money for a quality valve. Nothing is worse than having an emergency and discovering your emergency shut off valve doesn’t work!
You must have a backflow preventer on your irrigation system if it is connected to any water system that is used for drinking water. In some places this includes well water, even if your well is not used for drinking. In most places this is the law, everywhere else its just the smart thing to do. THE IRRIGATION VALVES ARE NOT SUFFICIENT TO STOP BACKFLOW. This website has a very detailed article on backflow preventers that will help you figure out why, where, and guide you step-by-step in selecting which one to use. See Everything You Need to Know About Backflow Preventers.