Purple pipe carries reclaimed water, which is municipal wastewater treated to a high standard for non-potable reuse like irrigating parks, golf courses, and medians. Purple is the national color code for non-potable reclaimed water, and the pipe is marked do not drink. Never connect it to drinking water.
What reclaimed water is and where it comes from
Reclaimed water starts as ordinary sewage. At a treatment plant, it moves through several cleaning stages. These stages remove solids, organic matter, and germs. The result is clear water that meets strict health limits for non-potable use. Non-potable simply means not for drinking.
Cities put reclaimed water to work in places that would otherwise waste fresh drinking water. Common uses include:
- Irrigating parks, golf courses, sports fields, and street medians
- Watering farm crops and landscaping at commercial sites
- Industrial cooling, including power plants
- Aquifer recharge, where treated water is returned to the ground to refill the underground supply
In a desert city, this matters. Every gallon of reclaimed water sent to a golf course or a median is a gallon of drinking water that stays in the tap supply. That is the main reason Phoenix and other Arizona cities water so many of their parks and plants this way.
Why the pipe is purple
The purple color is a national standard. The water industry adopted Pantone 522C purple as the marker for non-potable reclaimed water lines. AWWA recommended it in the 1990s, and APWA color guidance backed it later. The idea is simple. A worker who digs up a line, or a homeowner who opens an irrigation box, should be able to tell at a glance what is inside.
Color coding runs across the whole water system, not only reclaimed lines:
- Blue marks potable (drinking) water
- Purple (lavender) marks non-potable reclaimed water
- Green marks sanitary sewer and drain lines
Beyond the color, reclaimed pipe and its outlets carry labels. You will see "do not drink" or "non-potable water" stamped on the pipe and printed on tape around it. The same warning goes on signs at parks and golf courses. Sprinkler heads and hose connections on these lines often have a different shape or a locking cap. That way a garden hose cannot be attached by mistake.
How Arizona regulates reclaimed water quality
Arizona does not treat all reclaimed water the same. The state sorts it into quality classes under the Arizona Administrative Code. Each class is allowed for a set list of uses. The cleaner the water, the more uses it can serve, including those where the public is more likely to touch it.
The classes run from Class A+ and Class A at the top down through Class B and Class C. The highest classes carry the tightest limits on bacteria and cloudiness. That is why they are allowed for the widest public-contact uses, such as watering a park where children play. Lower classes are held to uses with little or no public contact, like some farm or industrial settings. The Arizona Department of Environmental Quality (ADEQ) runs the permit program. It decides which class a given water meets and what it may be used for.
The state sums up the goal plainly. As ADEQ puts it, "Recycled water is wastewater (sewage) that has been treated to a quality that is safe and acceptable for certain reuse applications." That one sentence captures the rule behind every purple pipe in the state. The water is truly treated and truly useful. Each class is matched to the right job rather than lumped together.
If you want the rules themselves, the quality classes sit in A.A.C. Title 18, Chapter 11. The reclaimed water permits sit in Chapter 9, Article 7. These same state rules also cover home graywater systems. So a homeowner reusing laundry water and a city watering a golf course both work inside one legal framework. For the household side of that, see our guide on whether graywater is legal in Arizona.
Why Phoenix uses so much of it
Phoenix is one of the country's leaders in water reuse. The city recycles about 97 percent of its wastewater rather than dumping it. Some of that flow goes to the Palo Verde Generating Station, the large nuclear plant west of the city, where it cools the plant. Palo Verde is one of the few major nuclear stations that does not sit on a river or coast. Reclaimed water from area cities does the cooling job a lake or river would do elsewhere.
The rest of the reclaimed supply spreads across the valley in the uses above. It waters medians and HOA greenbelts. It also fills recharge basins that bank water underground for dry years. For a homeowner, the point is simple. The purple pipe in a community is part of a planned desert water strategy, not a leftover or a second-rate hookup.
It helps to know which utility runs which water. Your drinking water and sewer service come from your city utility, such as City of Phoenix Water Services. Raw and irrigation water in the region often comes from SRP. Reclaimed water sits between them. It is a treated, reused supply that the city manages and the state regulates. If you have a question about a purple line on your property, the city water provider is the right first call.
Why you must never cross-connect it to drinking water
This is the safety rule that the purple color exists to protect. Reclaimed water is treated for watering and industry, not for drinking. It must stay fully separate from the drinking-water plumbing in any home or building. A point where a non-potable source can reach the drinking supply is called a cross-connection. That is the exact hazard the color code and labels are meant to prevent.
The danger is backflow. This is the unwanted reversal of water out of a reclaimed or other non-potable line and back into the clean supply. The EPA Cross-Connection Control Manual lists two ways it happens. The first is backpressure, when downstream pressure climbs higher than the supply. The second is back-siphonage, when supply pressure drops, for example during a water-main break. Either one can pull reclaimed water the wrong way through an open link. To stop this, reclaimed systems run on their own separate piping. They also use backflow prevention assemblies, which Arizona requires a certified tester to check. To learn how the hazard works, see what a cross-connection is.
For a homeowner, the rules are short and firm. Do not drink from a purple line or a sprinkler fed by one. Do not connect a garden hose, a hose bibb, or any household fixture to reclaimed piping. Do not let children fill bottles or play in reclaimed sprinkler spray where signs warn against it. If you are doing irrigation work and are not sure which line is which, stop and confirm with the city before you cut or connect anything. Want to see how reuse fits the bigger desert picture? Our overview of Phoenix water restrictions puts saving and reuse side by side.