(b) When operating a vessel on a body of water where the discharge of treated or untreated sewage is prohibited by the Environmental Protection Agency under 40 CFR 140.3 or 140.4, the operator must secure each Type I or Type II device in a manner which prevents discharge of treated or untreated sewage. Acceptable methods of securing the device include—

(1) Closing the seacock and removing the handle;

(2) Padlocking the seacock in the closed position;

(3) Using a non-releasable wire-tie to hold the seacock in the closed position; or

(4) Locking the door to the space enclosing the toilets with a padlock or door handle key lock.

(c) When operating a vessel on a body of water where the discharge of untreated sewage is prohibited by the Environmental Protection Agency under 40 CFR 140.3, the operator must secure each Type III device in a manner which prevents discharge of sewage. Acceptable methods of securing the device include—

(1) Closing each valve leading to an overboard discharge and removing the handle;

(2) Padlocking each valve leading to an overboard discharge in the closed position; or

(3) Using a non-releasable wire-tie to hold each valve leading to an overboard discharge in the closed position.

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Keeping in mind that the above was written before marine sanitation laws took effect and hasn't been updated or otherwise amended since, most coasties and local water cops will accept anything that clearly demonstrates INTENT to comply, whether it meets the letter of the law or not (e.g. keyed macerator switches, which didn't exist when that reg was written). It's only the "local yokel" with an advance case of Barney Fife Syndrome who'll give you any problems...and though they're mercifully few and far between, unfortunately you can't predict when you'll run into one.