Using Your Boat Head

What Kind of Boating Are You Going to Do?

Porta Potti Curve, Marine head/toiletYour selection of a head/toilet depends largely on how you use your boat and where the boat is located. Federal regulations require that any vessel equipped with an installed toilet also have either Type I, Type II, or Type III Marine Sanitation Device (MSD). Type I devices are only legal on vessels less than 65' that operate in an area not declared a Federal No-Discharge Zone. Type II devices are typically for vessels over 65', but can be used on any vessel as long as it's not an area declared a Federal No-Discharge Zone. And Type III devices, which are simply holding tanks, can also be used on any vessel. 

What Type of Head Should You Buy?

The type of head you buy should be based on use and available space. Weekend boaters on a boat less than 26' may find a portable head sufficient. The number of people you plan on having aboard and how often you want to take it to a pump-out station to clean it out also have a bearing on what you choose. For an owner who is planning on doing more boating or needs more capacity, a simple manual toilet with either a holding tank or a Type I MSD is appropriate. There are both manual and electric heads, manual being is a good choice if power consumption is a concern. If space allows, most boaters are more comfortable with a household size bowl than the small round ones common on the space-saving models. Always consider ease of servicing in the field when buying. You will probably have to do this someday.

What Type of Marine Sanitation Device?

This depends largely on the type of boating you do and your location. Most weekend boaters are satisfied holding their sewage in a tank and pumping it out at the end of the weekend. Holding tank size will depend on the number of people and available space on the boat. Boat manufacturers are required to supply a Type I, II, or III MSD. 

  • A Type I device is a flow-through treatment system which reduces the ratio of fecal coliform bacteria in the treated waste to no more than 1,000/100ml, and discharges no visible floating solids. However the Electr/Scan performs far better than this and out performs many public sewage treatment facilities ashore. See the article "Taking Care of Business".
  • A Type II device is a more thorough flow-through treatment, which reduces the ratio of fecal coliform bacteria in the treated waste to no more than 200/100ml, and discharges no more than 150 mg/liter of suspended solids.
  • A Type III device is a holding tank which performs no treatment, but simply retains waste for later pump out into shore-based waste handling facilities.

When considering a system, many people prefer a smaller holding tank in conjunction with a Type I device. This allows you to treat the waste before entering the holding tank, which eliminates the odors associated with holding tanks and still allows direct overboard discharge in areas not declared a Federal No-Discharge Zone. Although the standards have not been changed for many years, good Type I devices far exceed the Coast Guard requirement for fecal coliform and contribute only a miniscule amount of nutrient. Check with the specific manufacturer for test results if you're concerned about the amount of bacteria you may be putting into the water.

Basic Installation Requirements

Any installation made below the waterline that draws water from a through-hull should be protected with a vented loop on both the intake side and discharge side if access to a discharge through-hull also exists. This type of protection is not necessary for installations above the waterline, as back siphoning is unlikely. However some heads won't perform well with a vented loop between the thru-hull inlet and the suction pump. A vented loop is recommended on the discharge side to prevent odors from coming back into the toilet area and to prevent siphoning back. An installation that uses onboard pressurized freshwater must have a vacuum break between the solenoid and back bowl to prevent contamination of the water source. If the installation is more than several feet from the seacock, you may want to consider using a remote pump located between the seacock and toilet. Always keep in mind access for servicing.


To winterize your head, drain all water from the bowl, pump mechanism, and connecting plumbing. Close the intake seacock. Pump the toilet dry, then loosen the hose clamps and remove the inlet and discharge hoses, as well as any drain plugs. If the toilet is to be used in freezing conditions, use a small portion of nontoxic antifreeze, approved by the manufacturer, in the bowl to prevent damage from freezing.

Good Practice

Always close seacocks when you won't be aboard the boat for an extended period. Many owners have come back to find that through-hulls have siphoned water into their boat. If vents are not kept clean on vented loops, siphoning is more likely to occur.

A sulphur odor is common when drawing salt or brackish water. If the boat is unused for several days the odor becomes very obvious. This can be minimized by using an in-line deodorizer or by attaching a short piece of hose to the intake and drawing freshwater through the system before leaving. Several companies, such as, for example, Raritan, make products specifically intended to minimize or eliminate head and holding tank odors.

Boats with holding tanks should always be pumped out after use. This will eliminate odor and gas build-up in the tank. Some of the older flexible tanks are susceptible to explosion if left with waste and they get too hot and expand.

Type I systems should be cycled before leaving the boat to ensure that no waste is left inside untreated as this will also contribute to bad odors in the head .

Periodically check hose, clamp, and electrical connections to ensure smooth, uninterrupted service. Corrosion will cause a drop in voltage on electrical heads. Loose hose clamps can contribute to a flooding problem. Old hose or ribbed hose will contribute to odors. The fastest test for determining hose odor is to rub it with a rag and see if the odor is on the rag. If it is, replace the hose. Use only hose manufactured for marine head use. Other hose is more likely to accumulate calcium-like buildup inside and to cause odor.

The inlet line to your head should not be shared with any other accessory. Use only unrestricted non-collapsible hose between the inlet seacock and the toilet inlet.

If you are using a holding tank or treatment device, the inlet to the tank must be on top of the tank, and it should be at the farthest side of the tank from the toilet. This will prevent backflow into the toilet discharge plumbing.

See for additional information the article in BoatUS Magazine by Tom Neale entitled "Care and Feeding of Your Boat's Water Systems"


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