Graywater - Sailors for the Sea


Untreated water from your onboard sinks and showers, and the wastewater from cleaning your boat with detergents is a major polluter of the marine environment. Learn how to prevent graywater from impacting your local waters and wildlife. 

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Graywater is the untreated water from your onboard sinks, showers, washing machine, dishwasher and the wastewater from cleaning your boat with detergents, soaps and bleaches.

It’s a major polluter of the marine environment, especially in ports and coastal areas. In some states, graywater is considered sewage and regulated as such, making soap bubbles on the water’s surface a reportable pollution offense. Many marinas and harbors now have a no-discharge policy.

graywater, cleaning

How does graywater affect aquatic environments?

Similar to blackwater (sewage discharge), when graywater enters the aquatic environment, the associated chemical nutrients decompose in the water leading to less available oxygen for aquatic life. This influx of nutrients also promotes rapid algal growth, a process called eutrophication. Overrun by algae, ecosystems are eventually depleted of oxygen. The lack of oxygen can cause fish, shellfish and other aquatic life to suffocate, resulting in dead zones. 

How can you reduce the impact of graywater?

  • Research cleaners before you buy them. Check out Non-Toxic Cleaning Products for tips and suggestions. 
  • Use water saving devices such as low-flow showerheads and on-demand sink nozzles.
  • Use sink strainers to catch food waste and solid particles, and dispose of them in the garbage.
  • Whenever possible, use shoreside facilities for showering, laundry, dishwashing, etc.
  • When at sea, retain your graywater for a pumpout facility. If this is not possible, treat graywater as if it were sewage, and only discharge if you’re at least 3 miles offshore.
  • Try water-only wash downs. Often times they can do the trick when cleaning your boat.

graywater, cleaning, soap, washdown

Did you know?

  • Some marinas have pumpout facilities specifically designed for graywater.