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Use and Maintenance

Operating a Sun-Mar is easy. Begin by adding some Compost Sure peat mix and some Microbe Mix to the Bio-Drum. Both Compost Sure and Microbe Mix are included with all units.

Initial Start-up

These instructions are meant for initial startup of the composting system. As we used to say almost 20 years ago, it's just like baking a cake - you just have to add the ingredients and stir! Please note - normal toilet paper is part of the mix - it is a carbon source and you can use as much as you do with a regular toilet. No special toilet paper or decrease in usage is required!

Begin operation by carrying out the start-up procedure described below, and then continue with the "Ongoing Toilet Maintenance" routine. It normally takes six weeks before a compost is properly established. You will know that this has happened when:

  • Compost volume increases more slowly
  • Compost turns black and becomes loam-like
  • Toilet paper decomposes within a few days

3-4 gallons of peat mix (half the 30 litre/8 gallon bag provided) to the drum.
  • Provides carbon base and initial mass for compost.
Add 1/2 Microbe Mix packet at startup, other 1/2 in two weeks (or on next visit if in cottage use).
  • Adds necessary microbes which will break down the compost.
Sprinkle About 1/2 gallon of warm water into the drum.
  • Moistens the carbon base.
Plug In Power cord on unit to get fan and heating element working (electric models only)
  • The unit is ready for use.
Spray "Compost Quick" enzymes into drum before and after mixing. Coat the evaporation chamber with it before using the unit.
  • Speeds start up of compost by acting as a catalyst to assist bacteria.
  • Prevents possibility of start-up odor in the evaporation chamber.
Rake Loose peat moss from the evaporation chamber until the compost is established, which takes approximately 6 weeks.
  • Until the compost is active, some peat mix may fall through the screen or drum door into the evaporating chamber.

Now use your Sun-Mar like a regular toilet. Toilet paper is easily decomposed in a Sun-Mar. There are only two things that you have to do on a routine basis:

  1. Rotate the drum.
  2. Add bulking material at the rate of a cupful per person per day.
Bio-DrumWhen it comes time to empty, you are never dealing with fresh waste; when the drum is 1/2 to 2/3 full, you rotate the drum backwards by releasing the drum locker and dump some compost into the finishing drawer. Leave it there to finish batch composting for 3-4 weeks. See details in table below.

Ongoing Toilet Maintenance

    The procedure below is designed to keep the compost:
  • Moist, But Not Too Wet
  • Well Aerated & Mixed
  • Well Balanced and Aerobic

We recommend the use of our compost accelerators: Compost Sure, Compost Quick and Microbe Mix.





1 cupful (or 2 handfuls) of Sun-Mar Compost Sure (or 50/50 mixture of peat moss and non-cedar wood shavings) to the Bio-Drum after every bowel movement. This usually represents one cupful per person per day of use.

For more details see Advice on Compost Bulking Material.

If you have a central unit, peat mix only needs to be added when you do your rotations at the end of the weekend (cottage use) or once every 2nd day (residential use).

  • Maintains the carbon/nitrogen balance

  • Absorbs Liquid

  • Helps oxygen penetrate for aerobic composting
Turn Handle To Rotate Drum 4-6 complete revolutions, three times a week when in daily use.

If used only at weekends, turn only on departure.
  • Mixes and oxygenates the compost
Unplug the unit if you are leaving for a period of more than a few days. If you are leaving one weekend and coming back the next, you may unplug the unit.

Consider installing a timer to shut the unit off after 48 hours to evaporate excess liquid.
  • Conserves power and keeps compost from drying
Add Water approximately 1/2 gallon of warm water before leaving if you are leaving for a period of more than few days, or if the compost appears dry.
  • Keeps compost moist
Empty some compost into the finishing drawer when the drum is 1/2 to 2/3 full. It is 2/3 full when the compost reaches a level about 2-3 inches below the drum door when the door is open.

To empty some compost into the drawer, pull the drum locker button and rotate the handle counter-clockwise (to turn the drum clockwise). Turn at the same speed you would normally do for mixing.

If necessary, use the rake to level the compost in the drawer. If there is
not enough compost in the drawer, turn the drum backwards (clockwise)
again 1 rotation.
  • Moves some compost to the next stage for finishing

  • Ensures that the drum does not get too full
Leave the compost in the finishing drawer to finish for 3-4 weeks or until you next need to remove compost from the drum.

If your unit is used seasonally and not too heavily, you may not have to remove any compost at all during the season. In this case, follow the Annual Start-up Procedure in the spring.
  • Provides extra time for composting to be completed

Winter Use

Sun-Mar composting toilets serve as a reliable year-round facilities when prepared for continuous or periodic use during the cold winter months. If you use your cabin only once in a while in the winter, the unit may be used as a holding tank during this time.

If your Sun-Mar will be in use every weekend in the winter, or used continuously in a residence, the temperature must be kept above 55 degrees F at all times to keep the compost going. Click here for more information on winter use of composting toilets.

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