By the time I built my Caledonia yawl in 2003, I had done enough cruising to understand that I needed a boat that was not designed only for the usual functions while making way. Whether I sailed, rowed, motored, or even stayed put on any given day, I knew that every day I would need to eat and sleep. Two cruises up the Inside Passage made it clear that there were not always places to camp and even if there were, the inevitability of biting bugs and the chance of biting bears kept spending nights ashore out of the picture. I redesigned the yawl’s interior to include accommodations for cooking, eating, and sleeping.

That made life aboard much more comfortable, but I hadn’t given enough thought to another certain daily occurrence, using the toilet. I remedied that oversight with my next cruiser and built a place for a small porta-potti. Aside from the convenience it provides, it minimizes dependence on shore facilities and frees me from the less convenient system of wrap-it-up-and-pack-it-out I had practiced when I was camp-cruising by kayak.


The Dometic 972 is the first porta-potti I bought. (I later bought a second for my son to use on his boat.) It is 12-1/2″ tall, 14-1/2″ wide, and 16-1/2″ from front to back. Empty, it weighs 11.9 lbs. Its upper half has a 2.3-gallon freshwater tank for flushing, and is rated for up to 26 flushes.

Photographs by the author

The Dometic 135 has a push button (upper left) for the pressurized flush, and a gauge (lower right} to indicate the level in the holding tank.


Made of ABS plastic, the Dometic is the heavier of the two toilets and is more rigid.


The holding tank has a a pivoting spout and a twist valve that remain open while pouring and to assure an even flow that’s less likely to splash.

At the back are a piston air pump to pressurize the tank for push-button flushing, and a threaded cap for the freshwater fill. The lower half houses the holding tank. A slide valve opens and closes the opening to the upper unit bowl and a clear insert in the front indicates the tank’s fill level.

A latch at the back holds the top and bottom together until it’s time to empty the holding tank. With the top removed, the tank is sealed by the slide valve and the capped pour spout. Both have rubber gaskets to make them airtight. The pour spout pivots to an angle convenient for emptying the tank into a plumbed toilet, and a small vent, when opened, assures a smooth, even flow.

The Thetford 135 is constructed in much the same way, and is 12-1/4″ tall, 13-1/2″ wide, and 15″ front to back. It weighs 8.9 lbs. The 2.6-gallon freshwater tank is rated for an average of 27 flushes, and a bellows-type water pump does the flushing. (The instructions indicate there is a piston pump option, but I can’t find it online.) The bottom half has a push-button air vent and a recess for storing a container of deodorizer.

This Thetford 135 doesn’t have an indicator for the level of the holding tank.


The Thetford, also made of ABS plastic, is slightly flexible and impact resistant. The glossy finish is easy to clean.


The Thetford’s air valve is a spring-loaded push button. With the right grip on the handle, you can hold the button down while pouring.


Both porta-potties have bracket kits for securing them to a floor to keep them from sliding around if the boat they’re used in heels or rocks. The lids and seats are removable for cleaning.

To prepare the toilets for use, I fill the freshwater tank and pour a liquid deodorizer and digester in the holding tank. It makes for an easier pour when I get back home from the outing.

Because I bought the smallest available porta-potties, compact enough to carry aboard my cruising boats, it was to be expected that they wouldn’t be as easy and comfortable to use as the toilets I have at home, which have higher and longer seats. The seat of my standard-bowl toilet is 15-1/2″ from the floor and the opening is 8-1/4″ wide and 10” long while the toilet I use most often has an elongated bowl with a seat 18″ high with a 12″ by 8-1/4″ opening. Although the porta-potties have seats with comparable opening widths of 8″, they are only 12″ high. I can elevate the porta-potties by rearranging floorboards, but the short opening of the seats takes some getting used to. The Dometic’s is 8-7/8″ long and the Thetford’s 9-3/8″, so a bit more concentration and attention is required by the user. I don’t do as much reading on the pot as I do at home, but I have done a bit of rowing.

I have used the Thetford on my recent cruise on Baker Lake and the Dometic on several solo three-day cruises and on a weekend cruise with four relying on it exclusively. I have always had capacity remaining in the holding tank of both porta-potties.

A neat trick I picked up off the web for leaving a porta-potti clean for the next user is to give the bowl a spritz of cooking oil from a pressurized can. Pam is a well-known brand; I use a house brand of organic extra-virgin olive oil. It comes in handy in the galley too.

Emptying the holding tank of either porta-potti is easy—just pivot the spout, uncap it, open the air vent, and pour the waste into a toilet at home. I follow up with a few rinses until the water I pour out runs clear. I can’t really say how well the deodorizer works—I always revert to a habit I picked up when I was changing my kids’ diapers and wear my workshop respirator with the charcoal filters for organic vapors.

I still make rest stops at parks, but more often I’m in undeveloped places where there are no facilities. There, my porta-potties make it much easier to leave no trace.

Christopher Cunningham is the editor of Small Boats Magazine.

The Thetford 135 is sold through Amazon and Walmart for $84. The Dometic 972 is listed by the manufacturer at $101, and a 970-series is sold by Amazon for $120.

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