A toilet replacement can mushroom into a “more-than-you-bargained-for” project if you must replace the drain fitting and/or the wood supporting the toilet. If your old toilet is swaying like a porcelain hobby horse, the wood framing under it may be rotted. To do the replacement, you'll have to fix this framing, and that calls for digging into the floor under the toilet, or the ceiling below it.
It's harder to tell if you'll need to do serious work on the drain. You can get a hint from the overall condition and age of plumbing in your house. Consider also how well the old toilet flushes (although a drain cleaning may be the only thing standing between you and a straight flush).
No question, this could involve some work, but here's another way to look at it: If your house needs the work, somebody's gotta do it. If you're game, that somebody might as well be you. And by digging in, you stand to save a bundle on the repair!
It's a fact: New toilets usually flush better than geezer toilets. And they may even harmonize better with your color scheme than harvest gold or avocado.
A third reason to replace a toilet is entirely practical: If the seal under the old toilet is leaking, water will eventually rot the wood framing underneath. That, my friend, is a drag, and it's a good reason to occasionally replace the seal under a toilet—something that, I guarantee, nobody does!
Toilets are usually shipped in two pieces: the bowl, which mounts to the floor; and the tank, which mounts to the bowl. You'll spend most of your time mounting the bowl.
Step 1: Out with the Old
It's usually easy to remove an old toilet. Shut off the water supply at the little valve, called a stop, beneath the toilet. If the valve handle sticks, loosen the big nut under the handle one quarter turn, as indicated in the following photo, close the valve, and retighten the nut.
Remove the water supply line—either a hose or a tube—by unscrewing the big nut at the valve end. In most cases, you'll be replacing this line with a flexible hose, but don't trash it yet. Bring the old hose to the store so you are sure the new water supply will connect to the shutoff.
Now pop off the decorative caps and loosen all bolts at the bottom of the toilet. (Look around; one may be hidden in back.) If the bolts don't want to move, try locking pliers. Don't worry if they break off; you'll be replacing them anyway.
Pull out the old toilet and cover the drain with a rag.