Install a Freshwater Head

Do It with Fresh Water!

Your boat will smell sweeter with a freshwater-flush toilet. You’ll make fewer stops at the pumpout station, too.

Vacuflush system

Frank Shumway, if he is still on this planet, probably doesn’t remember me, but I remember him well. We sailed through a hurricane together in 1972, on the way to Bermuda—a nasty couple of days. But that’s not why I’m thinking of Frank now. It’s because of Shumway’s rule of marine-toilet operation: When you’re finished with the head, pump it at least 20 strokes to clear the discharge line. That way, you won’t get a septic tank pong from waste left in the hoses. 

Following the Shumway rule kept our Bermuda-bound boat smelling sweet, even under the worst of conditions. We got some arm exercise from all that pumping, too, courtesy of Wilcox-Crittenden: The pump handle on our top-of-the-line Skipper looked like the shifter on a Mack truck. None of those namby-pamby electric heads for us! Wilcox-Crittendens today, incidentally, are built by Thetford ( as part of their Tecma line.

But that was long ago, when a marine toilet drew water from the sea and discharged waste back into the sea, when there was no holding tank to smell or leak or overflow, and you could use massive volumes of water to flush without worrying about finding a pumpout station. But the same year Frank and I, and ten other wet, wind-swept guys, enjoyed the hospitality of the Royal Bermuda Yacht Club after the storm, the U.S. government passed the Clean Water Act of 1972, mandating more environmentally friendly handling of waste. 

No Flushing Allowed

After a two-tiered phase-in, by 1980 the Act required virtually all boats with installed heads to have a Marine Sanitation Device (MSD) either to treat sewage before discharge or hold it (in a holding tank otherwise known as a Type III MSD) for a later, legal pumpout. As a result, ship’s plumbing became complex as folks devised Rube Goldberg-inspired arrangements to both comply with, and circumvent, the new rules. (In addition, I reckon sales of Y-valves increased at least 1,000 percent.) Shoreside pumpout stations were rare in the early days of the Act, so it was often problematic to empty a filled holding tank legally, and onboard discharge pumps frequently were activated on the sly.

When you think about it, things were a lot simpler in the days of the cedar bucket although comfort issues often arose. More to the point, have you ever used a cedar bucket for bodily functions? If not, it’s worse than you might imagine, unless you rig some kind of seat. Back in the day, my dad bought a wooden seat for ours from the Crow’s Nest, an old-time New York City ship’s chandler. A modern version is still available: The TODD Bucket Potty Seat ( will fit a 3- or 5-gallon pail; West Marine sells them for $42. But hey, don’t let the EPA catch you dumping that pail overboard.

At any rate, today there are plenty of pumpout stations, so the cedar bucket has more or less faded from the scene and boatmen have mostly made peace, or at least a truce, with the holding tank. Nevertheless, you can make it a better shipmate. There are easy, relatively inexpensive cures if your tank emanates odors that remind you of grandad’s farm (see “Pungent Plumbing”), but if you want to go whole-hog and totally purify onboard atmospherics and aromas, upgrade your present seawater toilet to a freshwater-flush model. Your boat will not only smell sweeter, but the new toilet’s reduced water usage will cut down on your trips to the pumpout station.

Vacuflush system illustrated

Pungent Plumbing

If your freshwater system still has holding-tank halitosis, chances are your plumbing is out of whack. Hoses don’t stay odor-resistant forever, connections can leak, Y-valves start to drip, and so forth. Or maybe you’re just not practicing proper tank maintenance. So before you drop big bucks on a new head, give your sewage system the once-over.

First, check for the obvious—a leaky holding tank. A thick-walled rotomolded polyethylene tank will stay tight and odor-free for many years, but sometimes builders skimp. Look for moisture and drips, bulging sides, and weeping fittings. Use your nose as well as your eyes. If the tank is made of metal, replace it—acids in waste have probably eaten pinholes through it. (I was once saddled with a black-iron holding tank and it wasn’t pretty.)

Odor can permeate hoses that look fine. Marine sewage expert Peggie Hall, author of Get Rid of Boat Odors, says to wet a clean rag in hot water, wrap it around the hose and let it cool. Then take a whiff: If the rag smells, the hose is permeated. Check each hose, replace any that fail the wet-rag smell test. Use only top-quality odor-safe hoses; Trident Sani Shield #101 and #102 ( and SeaLand Odorsafe ( are both good. Double-clamp them.

Don’t overlook the vent. Vent lines should be as short, straight and horizontal as possible, and be larger than the 5/8-inch tubing most builders use—at least 1 inch. More fresh air in a holding tank promotes the growth of aerobic bacteria, which break down waste with minimal odor. Anaerobic bacteria, the kind that thrives in low- or no-oxygen conditions and lives in the human digestive tract, create the eye-watering holding-tank pong that reminds us of cow pastures on a hot summer afternoon. They do it by converting organic waste into methane. To fight back give your holding tank plenty of air by making sure the vent’s clear.

And every time you pump out the tank, rinse it with fresh water, especially if you haven’t switched to a freshwater-flush toilet. Fill it about a quarter full through the deck pump-out fitting, which will stir up the gunk on the bottom. Go for a ride to slosh the water around, and then pump it out again. And once a year open the inspection port and hose out accumulated sludge. Good thing pumpouts are free these days, or at least cheap!

The Sweet Smell of … Water? 

Even “clean” seawater typically contains cyanobacteria, which produce oxygen through photosynthesis; copepods, tiny crustaceans that other marine fauna love to eat; fish eggs and larva; algae and plankton. Sure, this is mostly small stuff, but if you don’t think it all adds up, remember that baleen whales live on it, and they need plenty of calories. And who knows what other pollutants are in there, especially near shore? Leave this mix in a closed tank for a while and you’ll have an odoriferous slime even without adding human waste. If you’ve ever been hit with the smell of swamp gas when pumping your seawater toilet for the first time after it’s sat for a while, you know what I mean.

Replace the sea water with clean, potable fresh water from the ship’s tanks and the brew will be less potent. Not only that, but a modern marine toilet charged by pressurized fresh water, like Headhunter’s Royal Flush system (, which sells for about $2,000, uses less water per flush because excess water doesn’t have to be pumped in from the sea to flush out the waste: When you flush, pressure water rinses and empties the bowl, and the amount of water used per flush is regulated by an electronic control. Water usage is typically measured in pints per flush rather than gallons, so for most of us freshwater use won’t be an issue: There’s plenty more back at the marina. And hey, if you’re planning on crossing an ocean, you probably have a watermaker.

Vacuum-flush toilets, as the name suggests, suck waste from the bowl into the holding tank, rather than relying on water pressure to flush it through. This requires minimal amounts of fresh water—SeaLand VacuFlush heads (, for example, use as little as a single pint per flush. After each flush, a vacuum generator re-establishes the vacuum for the next use. Upgrading to a VacuFlush system (a move that will typically cost you about $1,800) means adding not only a new toilet, but also the vacuum generator, so it’s more complicated than just swapping toilets. SeaLand sells vacuum-generator/holding-tank combinations—the vacuum components sit in a niche atop the tank. It makes for easier installation, and you get a new holding tank, too.

Most of the major marine-toilet manufacturers—Raritan, Thetford, Jabsco, Vetus-Maxwell SeaLand, et al.—build freshwater-flush toilets. The make and model that will work best for you depends on your specific circumstances, primarily the room you have to mount the new toilet and make the plumbing hookups. Consult with your yard manager or a marine-sewage expert to select a toilet and engineer the installation.

Don’t, Don’t, Don’t

Avoid like the plague all attempts to save a few bucks by re-plumbing a raw-water toilet to flush with fresh water. In the first place, most intake pumps will let pressurized water simply flow through the valves into the bowl. But from a safety standpoint, toilets not designed for freshwater flushing can let bacteria from waste migrate into your water system’s supply lines, and from there into your freshwater tanks. So even if you figure out how to make it work, don’t.

Holding Tank status panelThere is an option if you want to keep your present toilet, however. A FreshFlush device ( converts any raw-water head to fresh water without risk of contaminating the water tanks with E. coli or other nasty stuff, according to its manufacturer. It costs $299 and looks to be pretty easy to install: Mount the unit near the head, connect the inlet fitting to a freshwater feed (the manufacturer recommends tapping into the cold-water supply to the sink or shower), the outlet fitting to the head’s water intake, and use the head just like you do now—only difference is, the head’s intake pump will pull water from the FreshFlush, not the sea. The FreshFlush holds about a gallon of unpressurized water; after use, it refills automatically.

Marine toilets have come a long way since Frank Shumway preached his 20-stroke pumping principle. I think he’d be happy just to push the button once, and enjoy the sweet smell of fresh water.

This article originally appeared in the March 2015 issue of Power & Motoryacht magazine.

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