Dealing With Waste Aboard: Holding Tank 101

Back in the bad old days, having a marine head aboard was a relatively trouble-free proposition—you simply pumped the head and flushed the waste overboard. That was until the government banned the direct overboard discharge of sewage in 1972. From then on, having a marine head aboard could be more of a headache than a convenience.

Here’s the CliffsNotes version of the law: If you have a boat equipped with a marine head and operate it on inland and coastal waters, or inside a distance three miles from an ocean coast, you must have your head plumbed to a holding tank.

A marine holding tank.

A marine holding tank.

You can find holding tanks at any good marine supply shop and the pros there can also help you with any questions you may have about hooking it up. While there’s no getting around having a holding tank, there are some options available to you when installing one.

Holding Tank for Coastal Use

The simplest setup is one where the discharge from your head is plumbed directly to a holding tank. With this arrangement, waste travels from the head down a length of hose and into the tank—there’s no option for overboard discharge at all. Once the tank fills up, you have to find to a pump-out facility to have the tank emptied.

A simplified version of a coastal holding tank setup. Waste is pumped into a tank until such time as it can be sucked out at a dockside pump-out station.

A simplified version of a coastal holding tank setup. Waste is pumped into a tank until such time as it can be removed at a dockside pump-out station. Illustrations courtesy of Jabsco/Xylem Flow Control.

This is a great option for boaters who never plan on going beyond the three-mile offshore limit, where it’s legal to pump waste overboard. That said, it also marries you to the ritual of having to find a pump-out facility when the tank is full. When the tank is full, that’s it–you can no longer use your head.

Offshore/Coastal Hybrid

If you do plan on making any offshore hops beyond the three-mile limit, you may want to consider giving yourself the option to discharge waste both overboard or into a holding tank. This requires using a fitting called a Y-valve.

Installing a Y-valve allows you to divert waste either to the holding tank when you’re in coastal waters, or to an overboard discharge when you’re beyond the three-mile limit.

Easy, right? Well, the U.S. Coast Guard and most marine law enforcement agencies are a bit fussy about Y-valves. They generally require any Y-valve that is plumbed to an overboard discharge be padlocked to the holding tank position when a vessel is operating in coastal waters. While a cable tie seems a sufficient way to secure the valve in the correct position, the law doesn’t agree. Luckily, almost all Y-valves come with a means to attach a padlock.

The hybrid holding tank option gives you the ability to either pump your holding tank overboard (when it's legal), or have it emptied at a pump-out facility ashore.

The hybrid holding tank option gives you the ability to either pump your holding tank overboard (when it’s legal), or have it emptied at a pump-out facility ashore.

Yet another variation of the coastal/offshore setup introduces an additional Y-valve to the equation. With this system, the Y-valve diverts the holding tank contents either to a deck-mounted pump-out fitting, or to a manual or electric pump connected to an overboard discharge. This allows you to pump the holding tank out when you’re beyond the three-mile limit. Keep in mind that this setup comes with the same regulations with regard to securing the Y-valve when you operate in coastal waters.

Treatment Systems

Installing a treatment device is one way of getting around using a holding tank. There are a few on the market, but the LectraSan by Raritan is perhaps the most popular. It uses electrical current to turn the saltwater mixed in with the waste into an acid that kills harmful bacteria. Next, a macerator chops up the waste into an easily dispersed liquid before pumping it overboard.

A LectraSan treatment device. This unit uses electrical current to kill harmful bacteria in waste before macerating and discharging it overboard.

A LectraSan treatment device. This unit uses electrical current to kill harmful bacteria in waste before macerating and discharging it overboard.

You can install a saltwater feed tank to work with your LectraSan if you boat in freshwater lakes or rivers, but Raritan also manufactures a treatment device called a Purasan. It’s designed exactly for situations where no saltwater is present. There’s another treatment device manufactured by Groco called the Thermopure; it uses low-level engine or electric heat to kill waste bacteria before macerating it and dumping it overboard.

All of these treatment devices are legal in coastal and inland waters except in areas designated as No-Discharge Zones (NDZ), where the overboard discharge of any sewage (even treated) is prohibited. Visit the EPA website to find out if your boating locale is a no-discharge zone, or not.

No matter which system you choose, maintaining it properly will go a long way toward keeping it odor and trouble free. Keep an eye out here for an article covering the basics on marine head maintenance including which additives, cleaners, and snake oils work best.

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