Principles of Treatment

• Proper venting is essential to correct holding tank operation; keep the tank's vent hose free of obstruction. Good air circulation is a significant part of the process of decomposition, whatever the treatment additive you choose; and, if you use raw water in your boat's head, the circulation will help to eliminate any odors that may come from smelly water.
  
  

Types of Additives

• The main reason to add a treatment to the holding tank on your boat is odors. Even large boats are close environments and every inch of space is used. Odors from an untreated holding tank, like odors from the galley, can permeate every nook and cranny. The treatment options are both chemical and biological. Chemical products work reasonably well for a short time, but they don't encourage the decomposition of deposits that form in the holding tank. Chemical products also have potential consequences for the shore facility, which receives them when the tank is pumped out.
  
  Enzyme-based products, similar to those used in septic tanks, are beneficial over the short term, but require regular replenishment and more frequent pumping. This one factor makes them the most costly option.
  
  An aerobic bacterial treatment--they are also called bio-active treatments--help prevent odor from the tank and encourage the decomposition necessary for effective and cost-efficient holding tank operation. Like enzyme-based treatments, they have a low environmental impact on waste disposal facilities.
  
  Regardless of the type of additive chosen, read the Safety Precautions and comply with handling precautions for the product.
  
  

Forms of Additives

• Holding tank treatments come in two forms, each with pluses and minuses. Liquids can be poured into the toilet to be flushed into and treat the tank. However, if you spill the liquid, cleanup is troublesome and the product is smelly. The smell can be absorbed quickly if your deck is a natural material, like wood.
  
  Powders, like those used for septic tanks ashore, are troublesome when they lay up too long. A wet environment, like that of a boat, causes them to cake in their storage envelope and renders them ineffective.