Downstairs Toilet Installation

Updated February 21, 2017

Finishing a bathroom in a basement area adds value to the home. The value added can be significant. Doing the work yourself saves you money you would otherwise use to pay a contractor and it provides great hands-on experience for the homeowner. Understanding how to install a toilet is an important part of finishing a bathroom.

First Things First: Floor Preparation

The subfloor in a basement is constructed out of concrete. It is extremely important that the concrete around the toilet drain in the floor is level. If the floor is not level, the toilet will not seal correctly. An unlevel concrete floor will allow the toilet to rock back and forth. The rocking motion will allow the seal between the toilet and the floor flange to break and leak, which could lead to a huge mess.

To find out if the concrete floor is level, place a level directly on the floor, get on your hands and knees, and look to see if there is a space between the concrete and the level. The floor can either peak or dip. Peaked concrete is easily removed with an angle grinder and a diamond cup wheel. Grind the peak down to create a level surface for the toilet to sit on. Use a level to check your progress often. Dips in concrete floors are easily levelled using a self-levelling compound that is cement-based. Such a compound is mixed up in a five-gallon bucket and dumped directly over the concrete floor that requires levelling. After it has dried, the flooring can be installed and the toilet can be secured into place over the flooring.

The Next Step: Assemble the Toilet

There are many different toilet models on the market currently, and every one of them is assembled in a different way. Assemble the toilet according to the manufacturer's recommendations to avoid the possibility of leaking and flooding in the basement. This is usually involves a very simple and straightforward process. Many toilets are sold as a complete unit with all of the tank valves and flappers in place when the toilet is purchased. So all you have to do is bolt the tank to the base, attach the toilet seat, mount the toilet to the floor and install the water supply line between the toilet and the water valve coming out of the wall.

The Last Step: Mounting the Toilet

Toilet mounting is actually easier than it sounds. Many plumbing projects, because they involve water and many other more undesirable products, are intimidating to many people. But once the toilet is assembled according to manufacturer's specifications, it is ready to be installed. A toilet is held into place using two bolts that are inserted into slots around the drain flange in the floor. A watertight seal is created between the toilet and the flange with a wax ring. The easiest way to get a good seal the first time is to place the bolts in the slots in the flange first. Then carefully turn the toilet itself upside down to access the drain on the base of the toilet. The wax used to make wax rings is very sticky, so stick the wax ring directly to the bottom of the toilet. Carefully turn the toilet right side up, lift it up over the mounting bolts, and slide the bolts into the holes in the toilet base until the wax ring just makes contact with the flange. If the toilet sits directly on the floor without the wax ring making contact with the flange, a second wax ring should be stacked on top of the first wax ring to take up the space and make a tight seal. When the wax ring makes contact with the flange, gently rock the toilet into place over the bolts. Slide a washer over the ends of the bolts and screw the nuts onto the bolts by hand. Tighten the toilet nuts down with a wrench, but do not overtighten to avoid cracking the porcelain. Then attach the water supply line first to the toilet and then to the wall. Turn the water valve on slowly, allow the toilet tank to fill up, make any necessary adjustments to the tank valve system and test the toilet function. Check around the base of the toilet for leaking or seeping.

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About the Author

Kelly Nuttall is a student at Utah Valley University in Orem, Utah. She is set to graduate in the spring of 2011 with her bachelor's degree in technical communications. She has been writing for various websites since March of 2009.