Sewage: marine toilets, holding tanks and No-Discharge Zones

Oil, garbage & sewage · Power & sail

A boat with an installed toilet must have a working Coast Guard-certified marine sanitation device (MSD). Untreated sewage may not be discharged within 3 miles of shore or on inland waters; in No-Discharge Zones nothing may go overboard, treated or not, and valves must be secured. States add their own zones and rules.

If your boat has an installed toilet

• You may not operate a boat with an installed toilet unless it has an operable, Coast Guard-certified or labeled MSD (33 CFR 159.7(a)). EPA and the Coast Guard share this program under Clean Water Act section 312.
• Type I: a flow-through treatment device whose effluent has no more than 1,000 fecal coliform bacteria per 100 mL and no visible floating solids. Allowed only on boats 19.7 meters (65 feet) or less (33 CFR 159.3; 33 CFR 159.7(a)(2)).
• Type II: a flow-through treatment device whose effluent has no more than 200 fecal coliform per 100 mL and no more than 150 mg/L suspended solids. Allowed on boats of any length (33 CFR 159.3; 33 CFR 159.7(a)(1)).
• Type III: a device designed to prevent any overboard discharge, usually a holding tank. Allowed on boats of any length (33 CFR 159.3; 33 CFR 159.7(a)(1)). EPA says a composting toilet may count as a Type III device.
• Length for this rule is a straight line from the foremost to the aftmost part of the hull, parallel to the centerline, not counting bowsprits, bumpkins, rudders or outboard brackets (33 CFR 159.3).

Where sewage may and may not go

• Untreated sewage may not be discharged in US navigable waters, which include the territorial sea out to 3 miles from shore as 33 CFR 159.3 defines it (33 CFR 159.1; 33 CFR 159.3). Inside that line, sewage must be treated by a certified Type I or II MSD or kept in a holding tank.
• Treated effluent from a certified Type I or II device may be discharged in coastal waters, estuaries, the Great Lakes and connected waterways, lakes reached through locks and interstate rivers, unless the area is a No-Discharge Zone (40 CFR 140.3(a)(2)).
• No sewage at all, treated or untreated, may be discharged on freshwater lakes, reservoirs or impoundments that boats cannot enter or leave, or on rivers not navigable by interstate traffic (40 CFR 140.3(a)(1)).
• Beyond the 3-mile line, federal MSD rules do not restrict a recreational boat from emptying its holding tank; EPA describes Type III tanks as emptied ashore or at sea beyond three miles. Graywater from recreational boats has no federal rule, though states may have one.

No-Discharge Zones

• A No-Discharge Zone (NDZ) is water where discharging any sewage, treated or untreated, from any boat is banned. States get them through EPA under Clean Water Act section 312(f)(3), (f)(4)(A) or (f)(4)(B) (40 CFR 140.4).
• Some are written into the rule itself, such as Florida state waters within the Florida Keys National Marine Sanctuary and two stretches of the Hudson River (40 CFR 140.4(b)-(c)). Most others are EPA determinations listed on EPA's "No-Discharge Zones by State" page and map.
• Examples on EPA's list: all Massachusetts state waters, all of Michigan, Puget Sound and Lake Washington in Washington, Rhode Island within the 3-mile limit, Casco Bay in Maine, and Maryland waters such as Herring Bay and the Chester River. New zones are still being added; the latest on the list is from 2024.
• Before cruising new water, check EPA's NDZ list and map and the state boating or environmental agency it links to; states also publish pump-out locations.

Securing the toilet: the methods the rule accepts

• In an NDZ or other no-discharge water, secure each Type I or II device in one of these ways: close the seacock and remove the handle; padlock the seacock closed; hold the seacock closed with a non-releasable wire-tie; or lock the door to the head with a padlock or door-handle key lock (33 CFR 159.7(b)).
• Wherever untreated discharge is banned (inside the 3-mile line and on inland waters), secure each valve leading to an overboard discharge from a Type III system, such as a Y-valve to the sea or a macerator seacock: close it and remove the handle, padlock it closed, or hold it closed with a non-releasable wire-tie (33 CFR 159.7(c)).
• Locking the head door is listed only for Type I and II devices, not for Type III holding-tank systems (33 CFR 159.7(b)-(c)).

Pump-outs, portable toilets and the Clean Vessel Act

• Holding tanks are emptied at a shore pump-out station or a mobile pump-out boat or truck. Ask your marina, or check your state boating agency's pump-out list.
• The Clean Vessel Act grant program, run by the US Fish and Wildlife Service, pays state boating agencies to build, renovate, run and maintain pump-out and dump stations for recreational boaters, and to teach boaters where they are.
• A portable toilet ("porta-potti") is not an installed toilet, so the MSD equipment rule does not apply to it. Its contents still may not be dumped as raw sewage within 3 miles or in an NDZ; empty it at a shore dump station.

States add their own rules

• States may not set their own MSD equipment rules (houseboats aside) but can win NDZs and enforce the federal rules. Many have their own boating-sewage laws too.
• Examples: Wisconsin treats nearly all its inland and coastal waters as NDZs, except its waters of Lake Superior, the Mississippi River and part of the St. Croix River. Florida law requires Y-valves to be set or secured on all Florida waters and extends its raw-sewage ban farther off its Gulf coast. Check each state where you cruise.

The rules: 33 CFR 159.1 · 33 CFR 159.3 · 33 CFR 159.7 · 40 CFR 140.3 · 40 CFR 140.4

Sources disagree on Unit of the 3-mile limit for sewage (territorial seas) — left out rather than guessed. Check your local authority.

A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.