A revised primer on Marine Sanitation Devices

1. What a marine sanitation device is

An MSD is, in the language of the Federal Water Pollution Control Act (FWPCA) of 1972 and the implementing regulations at 33 CFR 159, "any equipment for installation on board a vessel which is designed to receive, retain, treat, or discharge sewage."¹ Federal law requires a certified, operable MSD on every vessel with an installed toilet (a "head"), regardless of vessel length, hull material, or use. A bucket head — that is, a portable toilet with no permanent plumbing connection — does not require an MSD. Anything that runs through fixed plumbing does.

The Coast Guard maintains a list of MSD-certified equipment; the EPA enforces the discharge rules; the State (Washington Ecology in our case) administers the No Discharge Zone designation; and the local Authority Having Jurisdiction (Port of Port Townsend Harbormaster, in our case) is the working contact for any dockside enforcement action.

2. The three types

Marine sanitation devices · 33 CFR 159 types

Type	What it does	Effluent standard	Where allowed	Practical examples
I	Macerates and chemically (or electrically) disinfects, then discharges overboard.	≤ 1,000 fecal coliforms per 100 mL; no visible floating solids.	Outside NDZ; not in any No Discharge Zone, including the Puget Sound NDZ.	Raritan Lectra-San; Groco Thermopure; Lavac with chlorinator pump.
II	Higher-treatment biological device. Discharges overboard.	≤ 200 fecal coliforms per 100 mL; ≤ 150 mg/L suspended solids.	Outside NDZ. Required on vessels over 65 ft, in some jurisdictions.	Headhunter Tidal Wave; Hamann HL-CONT; Microphor S-300.
III	Holds. Period. No overboard discharge.	None; the device prevents overboard discharge.	Anywhere, including NDZ. The default for boats inside the Puget Sound NDZ.	Polyethylene or stainless holding tank with Y-valve discharge plug and deck pumpout fitting.

For a recreational vessel under 65 feet inside the Puget Sound NDZ — that is, every boat we work on at Shop 7 — Type III is the operative answer. Type I and Type II are not, by themselves, illegal in the NDZ (you can own a Lectra-San and not have removed it), but their discharge function must be rendered "incapable of being used" while the vessel is inside the zone.²

3. The No Discharge Zone framework

Federal law allows a state to apply to the EPA for a No Discharge Zone designation over its waters, provided that the state demonstrates that adequate pumpout facilities exist within the proposed zone and that the discharge of marine sanitation device effluent — even at Type I and Type II treatment levels — would have a measurable adverse effect on the protected water body.³

The Puget Sound NDZ was adopted on 9 April 2018 after a five-year public process and EPA approval; it became effective on 10 May 2018. It covers the entirety of Puget Sound and the Strait of Juan de Fuca within Washington state waters. The Strait of Georgia, immediately to the north, is governed by the Canadian No-Discharge regime, which has its own (slightly different) requirements; this is operative for any boat we work on that crosses into Canadian waters.⁴

The practical effect is: inside the NDZ, no sewage of any kind goes over the side. Treated, untreated, macerated, chlorinated — none of it. The only legal disposal is via a USCG-certified pumpout at a shore facility (the State Parks pumpout network and the privately-operated marina pumpouts).

Outside the NDZ — that is, more than 3 nautical miles from shore on the Pacific side of the Strait of Juan de Fuca — Type I and Type II discharge is legal. Type III discharge (the contents of a holding tank, dumped overboard via a Y-valve to a through-hull) is also legal outside 3 nm, with the discipline that the Y-valve must be returned to the holding-tank position before re-entering the NDZ.

4. Y-valves and closures

For a vessel that operates both inside and outside the NDZ — most cruising sailboats and Bristol Bay-bound fishing vessels — the standard install is a Type III holding tank with a Y-valve cluster that routes the head's discharge either to the holding tank or to an overboard through-hull. The Y-valve makes the boat compliant in both jurisdictions; the discipline is the operator's.

The Coast Guard requires, on any vessel with overboard-discharge capability operating inside an NDZ, that the overboard side be rendered "incapable of being used" while in the zone. The relevant language is in 33 CFR 159 Subpart A.⁵ The accepted compliance mechanisms are:

• A padlocked valve handle (locked closed), with the key kept off the boat or on the operator's person.
• A removable valve handle, removed and kept off the boat while in the NDZ.
• A wire-tied valve closure that requires deliberate breaking (a single-use plastic seal in the marine-industrial standard, or a heavy-gauge stainless safety wire).
• A bolted-down closure plate over the through-hull on the inside of the hull (rare; effectively a permanent removal).

What the Coast Guard inspector cares about, on a dockside inspection, is documentation. The shop's standard install includes a printed closure-mechanism photograph in the as-built install report, with the boat's USCG documentation number and the date. We hand a copy to the owner; we keep a copy in the install file; the owner provides a copy to any state or federal inspector who asks.

5. What we install and why

Our standard Type III install is: a 25–45 gallon cross-linked polyethylene (XLPE) tank from Ronco Plastics (custom-fabricated to fit), with all top-mounted fittings; a Raritan PHII manual head; a Raritan three-way Y-valve with a stainless-steel hasp-and-padlock closure on the overboard leg; a 1.5" Trident 101 series sanitation hose throughout; a 1" vent run to a clamshell vent aft with a Sealand vent-line filter; a Perko 1283-series stainless flush deck plate for the pumpout fitting (labeled "WASTE — DECK PUMPOUT — KEEP CLOSED"); and a SeaLevel ultrasonic tank-level sender feeding the boat's existing N2K bus where one exists.

The specifics vary by boat. The principles do not: top-mounted fittings, top-quality sanitation hose, vented and filtered, padlocked overboard, labeled deck plate. We have not installed an MSD without all six elements in five years.

The five recent feature installs in this issue all follow this template. See the F/V Cape Fox feature for the detailed Type III install on a Bristol Bay gillnetter, and the Lavandula feature for an electric-pump add-on to an existing Type III on a permanent NDZ vessel.

6. Pumpout discipline

The single largest pain point in living with a Type III on a permanent NDZ vessel is the pumpout schedule. A 20-gallon tank on a live-aboard cruiser with one resident requires emptying every six days; a 38-gallon tank with two residents requires emptying every five. The available pumpout infrastructure in the Salish Sea, mapped through Washington State Parks' pumpout program, is excellent for the recreational user but tight for the live-aboard who has to find an operational unit on a Sunday in February. The Pumpout Washington directory and the Pumpout Nav app are the working references for this; we recommend both.

For permanent NDZ vessels we increasingly recommend an on-board electric pumpout pump and a dock-foot extension hose — see the Lavandula install feature for the worked example. The hardware cost (about $400 in pumps, $200 in hose, $300 in deck fittings and hardware) recovers itself in saved dockside hours within two seasons for a live-aboard.

7. The four MSD failure modes worth naming

7.1. Blocked vent

The vent line allows the tank to fill without creating a vacuum at the head. A blocked vent — clogged with insects, sulfur-corroded residue, or a long-unreplaced vent-line filter — causes the head to stop pumping, the tank to fill past the vent fitting, and the eventual backup into the head. This is the single most common Type III failure call we get. Inspect the vent annually; replace the filter every two years.

7.2. Hose permeation

Marine sanitation hose, even the top-of-line Trident 101, has a finite permeation life — typically five to seven years before the smell of the contents starts coming through the wall of the hose. The fix is replacement; the diagnosis is a wet-rag-on-the-hose test (Practical Sailor's published method, which we have used since 2018⁶). We see permeation failures on Trident 101 at about year 7, and on lesser hoses at year 3–4.

7.3. Y-valve failure

The Y-valve itself, particularly in a brass-bodied valve, is subject to corrosion failure that can leave the valve stuck in one position. The discipline is to operate the valve at least once a season (which, paradoxically, is not the default behavior on an NDZ vessel whose owner has padlocked the overboard side and never touches the valve). Open the padlock once a season, swing the handle through its range, close it back. The valve will outlast the boat. Don't, and you will replace the valve.

7.4. Tank-level sender failure

Float-style senders fail at about year 5. Ultrasonic senders (SeaLevel, etc.) fail at about year 12. The failure mode is silent: the owner trusts the gauge, the gauge reads a third full, the tank is actually three-quarters full, and the owner books a 60-mile sail before discovering the tank is, in fact, overflowing. We recommend a manual dip-stick check at the start of any passage over 24 hours.

References