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 now have a no-discharge policy.

Why is this a problem?

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, causing fish and other aquatic life to suffocate, resulting in dead zones.


  • Always research your cleaning products. For environmentally friendly options, see Non-Toxic Cleaning Products.
  • 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 (blackwater), and only discharge if you’re at least 3 miles offshore.
  • Clean your boat with water-only washes, as most of the dirt on a boat can be removed with a brush and water. 

Green Boating Guide: