When installing a microflush toilet such as the SeaLand Traveler™ with a composter, remember that drainage is tricky. One pint (half a liter) of water cannot move solids in excrement and toilet paper laterally or horizontally unless the pitch is a 35 to 45 degree angle down from the toilet to the composter. The steep downward pitch required for one-pint toilets is far greater than that for conventional toilets, because a well-designed 1.6 gal (6.06 l) flush toilet has a drain-line carry of 59 ft. at ¼ in. per ft. pitch in a 4 in. PVC pipe. (A 6-liter flush toilet has a drain-line carry of 17.9 meters at 6.35 mm per meter pitch in a 101-mm PVC pipe.)

Issues of optimum pipe diameter versus pitch are critical, as a given portion of excrement and toilet paper will not move unless there is sufficient water behind it to push it through or to lift and float it through the pipe. There is an optimum pitch and pipe diameter for every mix of solids and liquids:

• If the pitch is too shallow, solids will drop to the bottom and the liquids will slowly seep away.
• If the pitch is too great, then the liquids will precede the solids and the solids will drop out.
• If it is correct, the flush surge will lift up the solids and carry them down the pipe.
• If the pipe diameter is too large, then the sidewalls of the pipe will not be scoured by the water, and the energy in the water will be too diffuse to move the solids.
• You might not know that a problem exists until several portions of solids have blocked the pipe – and then it is too late for a quick and easy solution. For a low-flush installation, consider providing removable clean-out fittings at each end of the horizontal pipe run to provide easy access should a blockage occur.

A licensed plumber should make the connection with an appropriate flange on top of the composter to accommodate the toilet drain line. One innovative plumber we know used a plastic flow flange that would normally be used to connect a flush toilet to the drain line and to the floor. A union (a threaded plumbing fitting designed to be routinely separated) should serve as a quick disconnect should it be required. Hard connections, such as solvent welding, are too permanent for this purpose.