The Effect of Tap Water on Plants


Often, the path of water to the tap is not direct; it travels through a water utility and municipal water supply. The treatment it receives can have an effect on plants it's used on.

Treated vs Well Water

City water often contains chemicals added to make the water safe for human consumption. Well water may or may not be free from chemicals and bacteria, depending on the location and natural structure of the aquifer.


Many municipal water supplies contain fluoride, which is a plant toxin. Perlite, a common soil conditioner that also contains fluoride, can contribute to fluoride toxicity. Let water sit in an open container overnight at room temperature to dissipate fluoride.


Chlorine, another soluble salt sometimes added in municipal water supplies to kill bacteria, will kill plant roots and foliage. Chlorine will also evaporate from water if left to sit overnight.

Water Softeners

Softened water raises the level of soluble salts in soil, affecting the ability of plants to use water. Sodium and boron, used in many residential softener units, have toxic effects. Periodically flush soil with fresh water or replace to minimize damage.

The Bottom Line

Narrow-leaved plants are most susceptible to brown lesions or leaf-kill due to tap water toxicity. Airing water at room temperature, flushing soluble salts and maintain proper soil pH make tap water safe for most plants.


  • North Carolina State University:Watering Houseplants
  • University of Wyoming Cooperative Extension Service: Soil Salinity, Salt Tolerance and Growth Potential of Horticultural and Landscape Plants
  • University of Minnesota Extension Service: Flouride Toxicity

Who Can Help

  • Pensylvania State University: Penn State Pointers: Tap Water and Plants
  • University of Connecticut: Watering Houseplants
Keywords: tap water, plants, effects

About this Author

Chicago native Laura Reynolds has been writing for 40 years. She attended American University (D.C.), Northern Illinois University and University of Illinois Chicago and has a B.S. in communications (theater). Originally a secondary school communications and history teacher, she's written one book and edited several others. She has 30 years of experience as a local official, including service as a municipal judge.