Systems & Propulsion

Practical Sailor recently tested an updated version of the SeaLand 20 HTS-VRT holding tank reviewed in our November 2011 test, which found the Trionic SP-2020 super premium holding tank to be the Best Choice. For this test followup, SeaLand sent us a tank with the inlet and outlet fittings firmly installed and sealed with pipe sealant, as the maker recommends. (Aftermarket tanks are typically shipped with fittings separate.) The re-test found the revised SeaLand to be leak free, but the Trionic is less expensive and showed less deflection.

In the December 2011 article, “Maintaining Stainless Steel,” you mention that there are hose-clamp makers that get the stainless-steel combination right, but never shared who those manufacturers might be. I’d love to know who’s your pick!

The quality of onboard living suffers when each flush of the head becomes public knowledge within minutes, and a boat that smells bad won’t be a part of your family for long. Practical Sailor tested three vent filters for holding tanks, from makers Big Orange, Vetus, and Dometic, and tested one homemade vent filter. When sanitary wastes are allowed to biodegrade in a closed tank, particularly with poor mixing and inadequate oxygen, anaerobic bacteria dominate. These bacteria particles can make a boat unpleasant or unlivable unless they are eliminated or contained. Carbon filters are one solution to the odor problem; they are simple, dependable and absorb a wide variety of odors.

To create a real-world test, we assembled a series of miniature holding tanks containing sanitary waste generously supplied by a 20-pound, 5-foot pet iguana named Ziggy. This was supplemented with other sanitary waste as needed. Seawater flush was used because saltwater is known to contribute to odor.

The effectiveness of activated carbon comes both from surface activity (a result of activation by partial combustion of coal or woody products) and the vast pore structure formed during this partial combustion. Anything that clogs the pores will dramatically reduce carbon life, potentially ruining it within minutes.

Although none of the test tanks or the test boat’s holding tank accumulated solids sufficient to restrict pump-out, we observed significant differences. While vent filters did not increase tank solids beyond what is normal in a poorly ventilated and un-treated tank, some of the subject tanks did better than others.

For a real-world test, we created a series of small but real-world holding tanks containing real sanitary waste. The sanitary waste was supplied by a 20-pound iguana. Ziggy already poops in a tray of water and we know this mixture to be plenty foul. This was supplemented with additional sanitary waste during the start-up period each spring. Seawater flush was used, as the odor problems associated with seawater are known to be more severe, the result of bacteria-reducing sulfate into more odorous sulfide chemicals. Tank tests were supplemented with field testing aboard a test boat on the Chesapeake Bay.

Before beginning a series of tests, we always involve the manufacturers. They have a wealth of information they are happy to share, in the interest of reducing problems with their products. In general, their advice forms a consensus.

In our 2002 holding tank test, SeaLand emerged as the winner. The material of choice for holding tanks continues to be rotationally molded linear polyethylene, which is light in weight, doesn’t corrode, allows for seamless tank construction, is relatively inexpensive, and won’t allow odors to permeate. This new test compares a pre-2009 model SeaLand tank to a new holding tank from Trionic Corp. The holding tank test looked at the tanks’ construction materials, price, size, valves, inlets, outlets, leaks, inspection ports, vent size, warranty, and performance-based panel deflection. Preventing threaded fittings from leaking was the hardest part of the test.

For those in colder climes, the only drag bigger than the end of the sailing season is the need to winterize engines, generators, and air-conditioning units in preparation for their long winter’s nap. Wandering the docks at the 2011 Annapolis Boat Show, we came across the Sea Flush, a new product designed to make the process relatively painless, eliminating the struggle to pull a cooling-system hose end or installing a “Y” valve in order to flush and winterize “raw water” cooling systems or the open side of a closed cooling system.