Science project

Determine the Effect of Gray Water on Plant Growth


Determine whether greywater can be used to water plants.


  • Greywater collected from different sources
  • Fresh, potable water
  • Empty plastic water bottles
  • Small pots for planting
  • Potting soil
  • Pinto bean seeds
  • Labeling tape
  • Ruler


  1. First, make your hypothesis. Can greywater be used to water plants? Does the type of greywater determine whether or not a plant will grow? What is the general relationship between greywater and plant growth?
  2. Collect greywater from different sources in labeled plastic bottles. This could be water you washed your hands in, water from washing dishes, bathtub water, or any other greywater source you can think of.
  3. Plant your seeds. Put 1-2 seeds in each pot with potting soil. Label your containers with the type of water you will water them with.
  4. Water each plant with the same type of water each day. Be sure to have a control group that is watered with fresh water. Be sure to water each plant with the same amount of water, regardless of the type of water being used.
  5. Measure the height of the plants once they begin to sprout. Record the date and height and measure daily.
  6. Compare which types of water help plants grow the best.
  7. Make other observations. Do you notice any difference in color from one plant to the next? Do you notice any differences in turgidity, or a plant’s ability to stand upright?


The fresh water will most likely produce the tallest plant. Depending on what is dissolved in the greywater, plants watered with greywater may or may not grow.


Many products now are labeled “green,” which often means they are environmentally friendly and biodegradable. Water with these types of dissolved chemicals may not be as harmful as water with normal types of soap and shampoo, which are likely to poison plants.

Many communities treat their greywater and use the water to irrigate landscapes and inedible plants. Avoid using greywater on plants that come into contact with people as this type of water could pose a health risk.

Disclaimer and Safety Precautions provides the Science Fair Project Ideas for informational purposes only. does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against that arise thereof. In addition, your access to's website and Science Fair Project Ideas is covered by's Privacy Policy and site Terms of Use, which include limitations on's liability.

Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.

Add to collection

Create new collection

Create new collection

New Collection


New Collection>

0 items