We all understand the old adage of what rolls downhill, right? Plumbers have certainly known that basic premise since the first toilet was invented, and that’s why drain lines need to slope from the toilet down to the sewer or septic tank.
Simple enough — until you’re remodeling a basement or other below-grade area and want to install a toilet that’s below the level of the main sewer line. If you have a project like that in your future, then you’ll have to consider a different strategy.
Sewage ejector pumps and toilets
One option to consider when it’s impossible to get the necessary natural slope for a standard gravity flow toilet is to use a sewage ejector pump. These powerful electric pumps are capable of handling solid waste as well as liquids, and most can process solids up to 2 inches in diameter.
As with any type of electric pump, sewage pumps are rated in horsepower, ranging from less than one-half to more than one horsepower. The size you need depends on the volume of material being handled and, most importantly, how far the waste material will need to be moved vertically.
This vertical pumping distance from the fixture to the main sewer line — called "head" — is crucial to sizing the pump, and will typically be limited to about 10 feet of head for solids and 15 feet for liquids.
For the typical sewage ejector pump installation, the pump and the float mechanism that activates it sit inside a polyethylene basin that’s approximately 30 gallons in size. There’s a 3-inch or 4-inch diameter intake line that brings waste into the basin, a 2-inch diameter discharge line with a backflow-prevention check valve, and a vent pipe. Most pumps are 115 volts, but some of the larger units are dual 115/230-volt models.
Another option is a specialized fixture called a sewage ejector toilet, which is designed for below-grade installations.
The typical sewage ejector toilet consists of a pedestal made of polyethylene, which acts as a base for mounting the toilet. The pedestal, which is about 5 to 6 inches high, can sit directly on the floor or can be recessed so that the toilet itself ends up level with the floor. Inside the unit is a set of impellers and a sewage ejector pump, which processes the waste and pushes it up to discharge into the main sewer line.
Some models of sewage ejector toilets are designed with the pump and related vent and discharge lines located far enough behind the toilet that it’s possible to construct a wall between the toilet and the pump equipment. This allows for a cleaner installation, and makes the pipes and equipment much less obtrusive.
Another possibility to consider, especially if you’re thinking green, is the composting toilet. Composting toilets eliminate the need for a discharge pump altogether, and give a boost to the environment as well. The toilet is fully self-contained, requires no water inlet, no connection to a sewer, and no chemicals, but does require an electrical connection and a vent to the outside.
Composting toilets work similar to a septic tank. Approximately 90 percent of the waste material entering a toilet is actually water, so the composting toilet utilizes a small electric heating grid and fan inside the unit to evaporate the liquids through the vent pipe. The remaining 10 percent of the waste material breaks down through normal bacterial action, and is converted naturally into a soil-type residue. This residue filters down through a grid into a collection tray located in the bottom of the toilet. In normal use, the tray requires emptying only about once a year.
Composting toilets are not only good for below-grade applications, but also work great in cabins, shops, warehouses, and other locations where the installation of the waste and water lines necessary for a standard toilet is impractical.
Sewage ejector toilets and composting toilets, as well as sewage ejector pumps and related fittings, are typically available by special order through plumbing fixture retailers and some home centers, or through your plumber.