Since 1981, I’ve installed numerous toilets and I’ve also helped unclog them and repaired them so they run quietly. Toilets may seem simple to you, but they’re actually quite complex.

So, how does your toilet work? Let’s start with the basics.

Most residential toilets connect directly to a hidden drainpipe which typically has a 3-inch inner diameter. Drainpipes have a curved passageway called a colon that will allow a 2-inch-diameter ball to pass through it easily. The pipe design shares traits with central vacuum cleaners, where the opening at the end of the suction wand and the wand tubing are a smaller diameter than the pipe behind the wall. The big idea? You want material entering and traveling through the pipes to be narrower than the pipe so as to prevent clogs.

The connection between the toilet and the plumbing drainpipe must be leakproof so that water and rank sewer gas can’t seep into your home. Sewer gas leakage is a chronic problem for many people, and it frequently stems from a failed seal between the toilet and the flange on the floor that serves as the drainpipe’s terminus.

A flange should sit atop a finished floor, but due to common installation errors it often does not. Sometimes a plumber installs a flange to a home’s subfloor, and sometimes during a flooring installation a contractor or homeowner buries a flange’s top surface below the new flooring material. When this happens, the wax or rubber gasket that creates the leakproof seal between the toilet and the flange cannot make solid contact with both the underside of the toilet and the top of the flange.

Once a toilet is bolted correctly to the flange, the gap between the base of the toilet and the floor should be grouted with regular tile grout. Tile grout dries solid, as brick and mortar would, and holds the toilet in place. Don’t use caulk for this task, as it remains flexible after drying. If your toilet wobbles when you sit on it, trouble lies ahead, as the seal will fail.


Water in the toilet bowl serves an important function. It prevents sewer gas and vermin from entering your home. All traps under sinks, tubs, showers, and floor drains do the same thing, but contain much less water in them than your toilet bowl. The large amount of water in the toilet bowl acts as a target for your bodily waste.

Clogged toilets are a classic homeowner headache, but you can unclog a toilet with little more than a bucket of water. (You can watch a video on to learn how.) Plungers also do the trick, in many cases.

Flummoxed about the fill valve in the tank of your toilet? It’s a simple valve, although it looks complex. If your toilet fills slowly or makes a whistling sound, you may need a new fill valve. Fortunately, they are inexpensive and you can typically install a fill valve in less than 30 minutes — assuming the shut-off valve under the toilet works.

Now I’ll talk about what not to flush down the toilet — specifically, those wretched flushable wipes. Adult wet wipes are the bane of sewer-plant operators. If you use them, never flush them down a toilet. Treat them like an infant’s dirty diaper, and invest in a lidded bathroom trash can specifically for soiled flushable wipes.

Flushing these wipes can lead to clogged drain lines, and hiring a drain-cleaning company will cost you hundreds of dollars. Avoid the problem altogether by using some common sense, a dedicated trash can and cooperation from the members of your household.

Tim Carter has worked as a home improvement professional for more than 30 years. To submit a question or to learn more, visit