Upgrading and Understanding Your MSD (Marine Sanitation Device)

The condition of your head and waste treatment system has a lot to do with how you enjoy spending time on your boat. But many boaters are intimidated by the thought of replacing their current head, or adding a waste treatment system.

We took on this project this Fall on our 87 Egg Harbor35, and discovered that, in just a couple of weekends, we were able to replace our head with an upgraded model, plus install a Lectra San Sanitation Device with very little trouble. And it was worth it! We do, however, recommend that you tackle this job when the boat is hauled, as you may need to add or replace through hulls.

The Raritan Lectra San Type I Marine Sanitation Device (MSD) is an innovative USCG-approved secondary sewage treatment system that allows a user to treat and discharge head waste in all but specified "zero discharge zones".

Many boaters find that they must regularly dose the holding tank with harsh chemicals to dissipate offensive odors, and often, due to lack of or inoperative pump-out stations, they end up discharging the harmful contents directly overboard.

Onboard treatment via a Type I MSD means that, in most bays and coastal areas, waste does not have to be retained in a holding tank. The overboard disposal of treated effluent has proven to be a realistic alternative for many boaters interested in fewer visits to pump-out stations. With this technology you can be environmentally responsible and compliant with all but "zero discharge zone" regulations, and with a twist of the Y-valve, the holding tank can be put back into use making the vessel fully compliant.

The Type I MSD accomplishes its waste treatment through maceration and electrolytic decontamination. When used in saltwater estuaries, a set of electrodes suspended in the treatment tank utilizes 12vDC from the batteries to chemically turn seawater into a diluted, short-lived solution of hypochlorous acid. The resulting oxidation reaction allows small amounts of chlorine, liberated from the seawater, to act as a disinfectant killing the pathogens in the treatment tank.

Raritan's Lectra San two-chambered, three-gallon tank retains effluent from the previous flush for treatment while expelling waste water that has completed the cycle. By the time effluent is pumped over the side, most of the acid has been neutralized, and with the additional dilution that's incurred as it enters the water column, the effect on the marine habitat is minimal. Type I MSD systems treat the effluent enough to significantly reduce pathogen levels, and the chemical reaction also lessens the biological oxygen demand associated with the waste water, two big steps in pollution control.

Each operational cycle includes a 10-second seawater flush of the bowl and about a 35-second pretreatment run of the macerator pump that's housed in the first chamber of the treatment tank. This step is followed by approximately a two-minute electrolytic production of hypochlorous acid, and mixer-like agitation that expedites the chemical reaction.

During the process, waste water moves from the first to the second chamber and after the mechanical/chemical treatment it is finally discharged overboard.

A microprocessor senses voltage, salinity and temperature of the water and controls the treatment process. In areas where salinity is low, a salt solution injection tank can be added to automatically provide an adequate amount of sodium chloride for chlorine release. The model we used, the LST/MC, actually initiates a treatment cycle each time the head is flushed. The process does require a fairly substantial house battery bank to keep up with the 12vDC demands. In terms of total energy used, the number is very modest, a mere 1.5 amp-hours per average two-minute treatment cycle. It's important to recognize, however, that this calculation is based upon a hefty 45-amp demand that's in place for a relative short period of time, and its impact upon the ship's battery bank needs to be understood.

All in all this means that if you're at anchor and using 30 amps worth of lights and other appliances, the piggy-backed treatment load associated with running the LST/MC can push the amp-meter dial to a hefty 75 amps. If the ship's battery bank lacks sufficient capacity, a significant voltage drop will occur, resulting in an even longer treatment cycle and much shorter battery life. The result of these electrical implications meant that the installation of a new head and a Type I MSD treatment system involves both an electrical and a plumbing upgrade. The former being a fringe benefit that can help out several other onboard systems.

Raritan's Crown II electric head was the natural choice for our upgrade installation. It affords the convenience of one-step push-button flushing and treatment. The unit also has its own built-in macerator pump and can be plumbed to a Y-valve so that discharge can be directed overboard if a vessel is making an offshore passage.


Prior to installing our MSD upgrade, we removed part of the old system which was comprised of a standard marine head and macerator pump that was plumbed to a small holding tank. In addition to not providing enough capacity for a couple of days of cruising, the odor emanating from old porous hoses had become quite objectionable. During the disassembly process we thoroughly cleaned all adjacent spaces and removed the offending hoses.

We were able to install the rectangular Lectra/San in a starboard side locker just forward of the head and double clamped the new hoses that were also added. Sharp bends in the plumbing were avoided and a careful installation proved as important as the initial choice of the equipment. At Anchor Bay "East" Marina, we hauled the boat in order to install a larger diameter discharge through-hull fitting along with a new seacock. While out of the water, we checked over the other through-hulls as well as running gear. Through-hull fittings are vital to the efficient operation of the system are essential to keeping the boat afloat. They need to be well bedded, securely attached to the hull, and electrically bonded to keep them as corrosion free as possible. The American Boat and Yacht Council (ABYC) publishes very specific guidelines pertaining to these fittings and how they should be installed. BoatU.S. is familiar with these guidelines and can help you better understand the right way to get the job done.

All through-hulls should be directly connected to a traditional seacock or ball check valve. If, during your upgrade, you find that this shut-off valve is leaking, difficult to operate, or shows signs of corrosion, replacement is definitely in order. Red brass plumber-type gate valves are not appropriate for underwater applications, they are more galvanically reactive than bronze and tend to leak and malfunction much sooner than marine-grade alternatives.

The LST/MC can be plumbed in different configurations depending upon your specific needs. It can handle effluent from two heads and will work with either electrical or mechanical versions. The effluent from the treatment system can be pumped directly overboard in all but "zero discharge zones", or it can be diverted to a holding tank if desired. It's important to keep in mind that the more hose length and splices that are introduced into the system, the more the chance of a leak. Attention to detail in the installation process always pays off in the long run.

Attention to detail isn't only a plumbing consideration, the electrical implications are also quite significant. Remember that it takes 45 amps to run the unit, and if the LST/MC is located a long way from the battery box, voltage drop becomes a significant issue. The best solution lies in wire size overkill accomplished with a heavy set of wires running between the distribution panel and the treatment unit. Heavier gauge wire won't, even under treatment cycle loads, cause excessive voltage drop at the unit. If there's already an anchor windlass on the boat you may be able to utilize its power cables since it's unlikely that you'll be using the head and hoisting the anchor at the same time.

In our installation, the single push-button control panel that actuates the treatment cycle was mounted on the side of a cabinet and easy to reach from the head. Wires leading to the LST/MC were carefully routed and secured with wire ties, as was the head pump wiring that lead to a harness originating at the breaker-protected head circuit on the DC distribution panel.

Both the marine head, as well as the cube-shaped treatment system were carefully fastened to the vessel. When under way in either a powerboat or a sailboat, loads on these components significantly increase, so it becomes important to not only carefully fasten the components to a secure base, but also to make sure that the base is carefully bonded or bolted to a sound structural part of the vessel.

In order to use the system, the battery switch activating the ship's battery bank must be in the on position and the breaker designated "head" also needs to be switched on. From this point all it takes to flush the head and treat the waste is the push of a button. In situations where salinity decreases, treatment time will increase, and the addition of a salt solution injection tank can lessen the length of treatment.

As with most technologically sophisticated systems found on modern boats, it pays to implicitly follow the manufacturer's step-by-step installation guidelines, winterize the unit according to the owners manuals and get to know what periodic maintenance is necessary. Installing the unit the right way includes using proper hose sizes, making sure that you're connecting to adequate diameter through-hulls, and above all paying careful attention to those seemingly insignificant plumbing and electrical details that can make or break a good installation.