This may seem like an odd topic, but I think all of us have been at a campground or picnic area where outdoor toilets are in use. Sometimes these facilities are relatively clean and odor-free, while at others — not so much. This topic arose from someone who also had questions about venting septic odors inside and outside the house.

Both of us have frequent experiences on fishing trips with outdoor toilets that are of the second type mentioned above. So, what goes into keeping an outdoor toilet odor-free? Since some service providers are called upon to regularly clean pit toilets, it may be helpful for you to offer some tips to those that are building and managing these facilities.

Several methods can be used to minimize odors from the pit: Chemical additives can be added, the pit and the upper structure need to be properly vented, seat covers should be airtight, and polyurethane paint should be used inside the structure to minimize penetration of odors into the wood.

Numerous products on the market claim to minimize odors. The owner or manager should try them to determine the most effective solution. Some only mask the odor, while others encourage bacterial activity to break down the solids. A generic product that has been proven effective is hydrated lime.

One cup of hydrated lime sprinkled periodically over the pit contents will minimize odors and aid in decomposition. A couple of cautions are in order. First, the compound is caustic so when using the product, proper clothing, gloves and mask should be used to prevent the compound from contacting skin and out of eyes or mouth. Second, if it is used too often it inhibits bacterial action and slows decomposition. It controls the odor but the waste breaks down, meaning the pit will need to be cleaned more often.

Ventilation Tips

Just as in a septic system, ventilation is the key to prevent odors in an outdoor toilet. It is easy to determine if ventilation guidelines have been followed; your nose will tell you right away. To minimize odors, insect-proof openings should be placed in the walls below the seat. A vent should extend from the underside of the seat board through the roof or up to a horizontal vent open to the sides of the toilet. Make sure the vent is flush with the bottom of the seat board and does not extend down into the pit. The gasses that cause odors are lighter than air and they will collect under the seat board if the vent extends into the tank, releasing into the structure when the cover is lifted.

The opening in the seat board must have a tight-fitting cover. The type of seat and cover used with a flush toilet is not satisfactory unless weather stripping or other sealing material is added to make the cover and seat airtight. The cover should be kept closed when not in use to prevent odors from rising into the structure. This is why most campground privies have a spring-loaded hinge that automatically closes the cover.

At the top of the structure there should be a screened opening on each side or preferably all the way around the top to allow air to pass through and carry away any odors that may be released inside. Any openings should be screened to prevent insect entry. Similarly, the door should be tight-fitting and have a self-closing feature to keep insects and other small animals out.

Using a polyurethane paint reduces the opportunity for odors to seep into pores in the wood. If odors have become trapped in the wood pores, a solution of disinfectant and trisodium phosphate, or TSP, can be used. The walls and ceiling should be scrubbed along with any other wood surfaces inside. After the wood has dried it can be painted with the polyurethane compound.

Extra Points

A couple of final points. If the pit has an earth bottom so the liquid part of the waste can seep directly into the soil, the bottom of the pit can be no closer to a limiting soil layer than the final soil dispersal area in a septic system. The separation distance must be maintained. If this distance cannot be achieved, the pit should be watertight just like any sewage tank and the waste removed periodically using a vacuum truck.

Most outdoor toilets we see these days have watertight pits. Even though decomposition occurs in the pit, over time the pit will fill up, requiring waste to be removed or the toilet moved to a new location.

Since the waste will be removed by a service provider, it is important the owner or manager is clear that the pit is not a receptacle for anything other than human waste and toilet paper. Every service provider who reads this can relate stories of unusual things they have sucked out of these pits. So just like a flush toilet, nothing goes in that hasn’t been eaten first! Except toilet paper.