Sewage Maceration Is As Gross As It Sounds | Hackaday

Day to day, few of us really contemplate what’s happening on a deep, mechanical level when we use the toilet. The business is done, the toilet is flushed, and we go about our day. However, the magnificent technology of indoor sanitation should not be sniffed at, given the manner in which it facilitates a cleaner, more comfortable existence for us all.

The vast majority of flush toilets rely on the benefit of gravity to remove waste from the house. This necessitates that the toilet be installed above the sewage lines that exit the house. For most installations at ground floor and above, this isn’t a problem. However, on occasions you may encounter basements or houses with rooms at lower levels where a regular toilet simply won’t work. Obviously, a pump is in order, but human sewage being a mixture of liquids and solids makes this impractical. Instead, it must be turned into a slurry that can be pumped; a process known as sewage maceration. Buckle up!

Sewage Maceration Is As Gross As It Sounds | Hackaday

How It Works

A macerator is, at its heart, essentially a blender for sewage, combined with a pump. They’re commonly used in the home when its desired to install a toilet at a level beneath the main sewer line, or to do so without drilling through the floor. Thanks to the pump, they don’t need to rely on gravity and can be used to move sewage tens of feet vertically and hundreds of feet horizontally.

Perhaps the most representative model of macerator for the home market is the Saniflo, which uses a mains-powered motor to spin a steel blade to chop the sewage into a slurry, before pumping it using a typical impeller design. These are often combined with special toilets with rear outlets that are otherwise uncommon in the US market, and can also be plumbed to use the pump with sinks and showers as well. Upon water and waste entering the toilet, a pressure switch is triggered that turns on the system, breaking up the matter with the blades and pumping it away. The limitation of this design is that the maceration blades can become jammed, particularly with fibrous material such as wipes or sanitary products. This can lead to results that are only humorous if they’re happening to someone else, as repairing a jammed system typically involves dismantling the unit and the sewer line, which is typically full of the horrible waste you were trying to get rid of and doesn’t typically have an on/off valve. Higher end models exist, which pack heavy duty “grinding” blades to break down such material, but no system is perfect and jams are still common.

The real issue with sewage maceration is not that it works, but that it sometimes breaks down, and when it does, it’s a filthy mess. A system of motors, pressure switches, and valves will always be less reliable than a simple hole in the floor, and more prone to failure. With the bonus of being installed below the sewer line, any maintenance will typically lead to a spill of raw sewage. It’s a peril this writer hasn’t experienced in 30 years of typical gravity toilet use; one must suspect few home maceration systems are quite so reliable. Regardless, it should lead any homeowner to think carefully about whether having a toilet in the basement is quite worth the complications.

Industrial Maceration

Of course, maceration isn’t just for the home gamer. Larger systems are used at the municipal level to break up waste and pump it through treatment facilities. This has become a more important issue in recent years, as more ignorant citizens flush wipes and other matter that doesn’t break up in water. Rather than attempt to educate the populace, many cities have simply elected to solve the issue with heavy machinery. Some manufacturers are even marketing heavy duty grinders to do the job. If the trend continues, it should be possible to flush a Hot Wheels by 2037 without undue repercussions from the local authorities.

While already familiar to the plumbing fraternity, we hope this article has served as an education in the how and why of pumping sewage. It can be done, and at relatively low cost — albeit with significant consequences when it goes wrong. May this aid your decision making process when it comes time to remodel your poolhouse, or when your significant other asks if the downstairs bedroom should have an ensuite. Good luck, and happy plumbing!