Use our tips to mitigate and even eliminate holding-tank odors.
By Pierce Hoover
Sunshine, clear water and a fresh sea breeze — the only thing that might spoil this moment is an unpleasant emanation from your boat's holding tank. Even if you started the season with a clean tank and a well-maintained system, things have a way of building up through the summer, sometimes with foul results.
Fortunately, there are ways to mitigate and even eliminate holding-tank odors. First among these is ventilation. While it might seem counterintuitive to want to direct airflow through the blackwater system, the reality is that holding tanks actually function best when the beneficial aerobic bacteria that live within the tank are provided with an ample supply of fresh air.
To ensure that these microbes get the oxygen needed to do their job, you should search out and eliminate any constrictions or low spots in the vent lines that could restrict the flow of air. You can also keep these beneficial bacteria alive and thriving by avoiding the use of cleaning chemicals that contain formaldehyde or bromine.
Also key to a healthy holding tank is a comprehensive waste-management plan. This begins, as you probably remind your guests, with being mindful of what is flushed into the tank to begin with. But some boaters don't extend this thinking to include the routine paperwork. The best choice is single-ply biodegradable RV/marine toilet paper, as it is designed to break down in the tank. Conventional double and triple-ply toilet paper can cause blockages, and no one wants that.
All tanks benefit from the use of additives. There areis a number of additive options on the market, and they fall into four general categories. Chemical treatments are the most common, and are very effective at odor control. But because they kill both odor and bacteria, the materials in the tank will not benefit from the natural process of organic breakdown. In addition, most chemical treatments are not environmentally friendly, and should not be used if you are discharging overboard in offshore waters.
Another popular option is a bioactive treatment that contains live aerobic bacteria. These "friendly" bacteria not only go to work breaking down tank waste, but also crowd out the "bad" odor-producing bacteria. In a well-ventilated tank they will multiply and thrive, eliminating the need to repeat treatments between pump-outs.
For more aggressive digestion of organic materials and odor neutralization, you can select either an enzyme additive or a nitrate treatment. Enzyme additives work quickly to completely emulsify paper and sewage and have extremely low toxicity, but they must be added regularly and have a limited range off effectiveness in terms of temperature and pH. Because these enzymes are sensitive to chemicals, heat and cold, the tank must be free from the residue of other treatment products.
Tanks that do not receive adequate airflow may benefit from a nitrate treatment. When airborne oxygen is in short supply, bacteria will produce hydrogen sulfide (the stinky stuff). Nitrates provide an alternative source of oxygen, which results in the production of nitrogen gas (odorless). Nitrates are also environmentally friendly, but require that the tank be free of residual chemicals.
Regardless of which treatment system you choose, the final key to odor elimination is to pump early and often. Waiting until the tank is full to the brim could result it an overflow that would fill the air vent or leak into the bilge — or back into the toilets. And when you pump, take the time to flush the tank with fresh water and repeat the process. Many boaters get into a rush and skip this step, but the extra couple of minutes a rinse may require will help ensure that those afternoon sea breezes don't carry any unwanted additions.
Other Boatkeeper tips featured this month:
- More Electronics from past issues.
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