If you are not connected to a municipal sewer system, pump your septic tank every two years. If your septic system was installed before 1974, it probably is allowing pollutants to reach the lake. The NH Department of Environmental Services can advise you. They may kill the bacteria your system needs to function properly, and can leach into the lake. These birds are a major source of both bacteria and phosphorus pollution.
Soaps contain phosphorus.
Choose non-phosphate detergents. Let latex paints evaporate until they are solid, then take to the transfer station. Save all oil paint waste for hazardous waste collection. Allow thinners to settle in a covered container, then reuse the clear portion and take the thick residue to hazardous waste collection. Herbicides and Pesticides.