Marine Sanitation:SeaLand Holding Tank Systems

If you want the Rolls Royce repository for fecal matter, you can drop a cool grand on a preassembled tank that incorporates discharge pump, vent filter, pressure relief valve and tank level indicator.


SeaLand Technology of Big Prairie, Ohio is not a diversified company. Once part of Mansfield, the largest maker of home toilets, SeaLand was spun off in 1984 and purchased by the Nelson A. Taylor Co., now Taylor Made.

Marine Sanitation:SeaLand Holding Tank Systems

SeaLand makes sanitation systems for boats and RVs and that’s about it. Its product line includes toilets, tanks, hoses, toilet paper and a considerable number of interesting accessories. Here we’ll look at a few of them, plus some odds and ends from other companies.

SeaLand president Ed McKiernan says his company is always looking for ways to make installation and use of its products easier. The easier a product is to use, the more likely it will be used, and in marine sanitation, that’s important…to containment and proper disposal of waste.

SeaLand’s new Holding Tanks Systems (HTS) are a good example. These polyethylene tanks—available in 28- and 40-gal. sizes—combine a number of accessories that previously had to be installed on bulkheads and shelves around the tank. From West Marine, they cost $449 and $499 with TankWatch IV level indicator and vent filter. Other variations of the HTS space-saving designs incorporate SeaLand’s electric diaphragm discharge pump, TankSaver relief valve, vacuum generator for use with VacuFlush toilets, and vent filter. All are preassembled and mounted on the tank at the factory. List prices range from $812 to $1,787.

SeaLand’s discharge pump is, in our opinion, the best available. We’ve owned several of them and never had a problem. It can be pumped dry without damage, which is especially important with a holding tank because it’s difficult to know when the tank is empty; and it is self-priming. It sells for $240 from West Marine.

Speaking of not knowing the fill status of a tank, the TankWatch IV level indicator ($244.69 list) utilizes probes that are positioned at the end of 1/2″ diameter tubes at different depths. Micro float switches activate lights on the display panel—Empty, Low, Mid and Full.

The TankSaver relief valve ($30.90 list) installs in a 3″ hole cut into the tank. It is designed to prevent damage to the tank from excessive pressure from a shoreside pump-out station. It’s basically a flapper valve with a ring of foam over the openings to prevent odors from escaping.

Lastly, an in-line vent filter is clamped to the tank to prevent odors from escaping, especially when the toilet is being pumped. Typically, the vent fitting is mounted on deck and forward so that escaping odors are blown aft toward the cockpit. Media in the filter is said to absorb the odors. It should be replaced every season. ($80.26 list) For a similar product, see the Odorbuster on the next page.

SeaLand’s polyethylene tanks are 3/8″ thick, more than any of its competitors. Tanks come with brass mounting spindles that are screwed to the floor and then fit into molded slots in the tank’s four sides.

The number of flushes possible with the 28- and 40-gallon tanks is 82 and 123 respectively. Size of the 28-gal. HTS is 30″ x 19″ x 19-1/2″ and weight dry is 40 lbs. The 40-gal. HTS measures 33-1/2″ x 20″ x 20″ and weighs 44 lbs. dry.

Diptube Kit
SeaLand’s HTS are equipped with diptubes, also sold as retrofittable kits for other tanks ($25 list). One of SeaLand’s distributors, Northeast Sanitation, brought them to our attention. The diptube is essentially a 1-1/2″ ID rigid PVC pipe with an elbow near the bottom so that the diagonally cut tube bottom has more pick up area than if the pipe were cut off at right angles. Part of the inspiration, here, according to McKiernan, was meeting Europe’s ISO standards, which require that the tank be emptied to a certain distance from the bottom.

Diptube kits fit tanks up to 30″ deep, come with a self-sealing cap and eliminate holes in the bottom of the tank, which, if they leak, could create a mess. By removing waste through the tank top, the chance of sewage sitting stagnant in hoses is minimized; as discussed in the hose test (page 16), this is a major cause of hose failure.

Seacock Interlock System
Perhaps you have never tried to pump the contents of your holding tank overboard with the seacock shut, but you can imagine what happens! The hose and fittings between pump and through-hull are pressurized…until something blows and what blows ain’t pretty!

SeaLand’s Seacock Interlock System is an electro-mechanical device that mounts on the seacock base and prevents the discharge pump from turning on if the seacock handle is closed. The device doesn’t work with all seacocks, only 1-1/2″ Conbraco ($76.29) and Groco ($92) seacocks and SeaLand T series pumps.

Installation of the Seacock Interlock System is a complication that on most small boats probably won’t be viewed kindly, but captains of larger yachts, who may occasionally suffer the consequences of well-intended guests and other crew—even, or especially, owners!—who try to fix things themselves, will find a measure of protection against system splatter with this device. The SIS can optionally activate a warning light on SeaLand’s TankMaster 4 display panel that advises, “Check Seacock.” The TankMaster 4 allows automatic or manual emptying of holding tanks and is intended to prevent accidental discharge. When entering a No-Discharge zone, a key-operated switch secures the discharge pump.

Toilet Night Light
This strange little gizmo is worth writing about just so we can repeat the packaging copy:

Marine Sanitation:SeaLand Holding Tank Systems

“Toilet Night Light™. The Ideal training device for boys and men alike. The first sure method for educating and training the ‘men in your family’…to once and for all ‘put the toilet seat down after use.’

“The Toilet Night Light™ also spotlights the target to prevent those messy misses and night-time accidents. It eliminates the need for harsh, bright overhead lights during the night. Soft light makes it easy to return to sleep. The Toilet Night Light adheres to the seat of the toilet, not the inside of the bowl making it safe and sanitary for everyday use.”

The light uses one AAA battery and is activated by a motion switch that in turn is activated by your Pavlovian-trained sons and husbands who veel remember to raise de lid or else you veel cut off der balls!

This lightweight piece of white plastic made in China sells for about $6-$8 at stores like K-Mart. You can call the 800 number listed below for the name of a retailer near you.

Odorbuster Holding Tank

Vent Filter
Like SeaLand’s inline vent filter, the Odorbuster from e-Marine is designed to prevent odors from escaping the tank and blowing aft to the cockpit.

The Odorbuster’s label asks, “Is that what’s troubling you, Bunky?”

“1. Holding tank odor wafts over the cockpit every time the head is pumped.

“2. Your boat stinks up the whole raft-up every time the head is pumped.

“3. Have you tried all kinds of additives that are supposed to control holding tank odor? Nothing seems to work.

“Odorbuster holding tank vent filter is the answer to your problems.”

The Odorbuster is made from a 12″ length of PVC pipe with end caps drilled and tapped for 1/2″ hose barbs. The inside is filled with some sort of filter media (charcoal?), held in place by a scrubby pad sort of material. The tube is mounted with two plastic mounting brackets with foam cushions and stainless steel screws.

Price is $29.95 each, very reasonable compared to SeaLand’s filter at $80.


Contacts- Northeast Sanitation, 69 Florida St., Farmingdale, NY 11735; 800/352-4323. Odorbuster, e-Marine, Inc., 2613 Key Largo Lane, Ft. Lauderdale, FL 33312; 954/581-2505; Toilet Night Light, Prestigeline Inc., 5 Inez Dr., PO Box 610, Bay Shore, NY 117067-0828; 800/776-5483 or 631/273-3636. SeaLand Technology, PO Box 38, 4th St., Big Prairie, OH 44611; 800/321-9886;