Recycled Water: Safe for Trees?

By Canopy Team on June 20, 2016

recycled water purple pipe

Recycled Water. Image Source: The Ripple Effect

As California’s drought persists, many people are concerned for the well-being of their trees, but are also concerned about reducing their water use. One way to cut water use is by applying recycled or gray water in outdoor landscapes. But are these water sources really safe for trees? Read on to find out. 

What is recycled water?

Recycled water is wastewater that has undergone several levels of treatment, including physical, chemical, and biological treatments.

The treatment and use of recycled water are regulated by the California Department of Public Health to ensure adequate safety and monitoring. Recycled water must be transported through a system of pipes that is completely separate from potable water pipes. Recycled water pipes are painted purple and must be clearly labeled. Recycled water is acceptable for human contact, but not suitable for drinking, swimming pools, or baths.

In our area, recycled water is produced by Palo Alto Regional Water Quality Control Plant, which exceeds most quality standards set by the state.

More info:

How do I get access to recycled water?

In Palo Alto and surrounding communities, you can get recycled water from the Regional Water Quality Control Plant (RWQCP). There is no charge for the water itself, but permits are required to obtain and use recycled water to irrigate commercial or residential properties.

Additionally, local companies such as RainDance and Purple Pipe Water Services deliver recycled and ground water to residents. You can work with them to design the optimal application method and frequency to save both water and trees.

Can I use recycled water to water my trees?

Yes, with caution—not for all trees, and only as a supplement to potable water. Recycled water is a drought-proof source of water that saves potable water and can be valuable in the landscape as a supplemental source of water. However, it’s important to exercise caution; most recycled water has a high salt content that can harm many tree species and woody plants.

Canopy’s recycled water recommendations:

  • Avoid spraying recycled water directly on foliage.
  • Confine applications of recycled water to lawn and other small landscape plants.
  • Near trees, limit application of recycled water to every other week, ensuring recycled water does not represent more than ¼ to 1/3 of the water applied to trees.
  • Local companies such as RainDance and Purple Pipe deliver recycled and ground water to residents. Work with them to design the optimal application method and frequency to save both water and trees.
  • Monitor signs of stress in your trees and plants — for example, changes in leaf color, early leaf drop, or wilting. Contact a plant health expert or certified arborist for advice on adjustments to your watering if changes in health are observed.

More info: City of Palo Alto Recycled Water FAQ.

gray water system

Gray Water System. Image source: Gray Water Wiki

What is gray water? Is it safe for watering trees?

Gray water is potable water leftover from household use such as baths, showers, and washing machines. It does not technically include water from kitchens or toilets, since these sources may contain contaminants.

It is perfectly safe to use gray water to water your trees and plants, as long as you use biodegradable soaps and shampoos.

More info:

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