The DIY Project That’s More Achievable Than It Sounds
Replacing a toilet is a plumbing project that reliably intimidates homeowners who haven’t done it before, and that turns out to be entirely manageable once the process is understood. The physical work involves disconnecting a water supply line, unbolting two bolts from the floor, removing the old toilet, cleaning the flange, installing a new wax ring, setting the new toilet, reconnecting the supply line, and verifying there are no leaks. Most homeowners with basic plumbing confidence complete a toilet replacement in 1–2 hours.
The toilet replacement article in this series (Vol. 11) covers the performance specifications for selecting a toilet. This article covers the installation process itself — the physical steps that translate a toilet selection decision into a completed, functioning installation.
Pre-Installation: What to Verify Before the New Toilet Arrives
Before purchasing a new toilet, measure the rough-in distance (the distance from the wall behind the toilet to the center of the floor drain flange — typically 12 inches in standard American plumbing). A toilet with a 12-inch rough-in at a 12-inch rough-in is the correct match; a 10-inch toilet at a 12-inch flange will have a visible gap between tank and wall. Measure before ordering.
Also verify: the available space in front of the toilet (the toilet bowl projects forward from the flange; measure that the available space accommodates the toilet’s stated projection plus adequate clearance), the space on each side of the toilet for minimum clearance per local code (typically 15 inches from center to any obstacle on each side), and whether the water supply shutoff valve operates — a valve that’s seized shut needs to be replaced before any toilet work begins.
Removing the Old Toilet
Turn off the water supply at the shutoff valve under the tank. Flush to empty the tank, then use a sponge or shop vacuum to remove remaining water from the tank and bowl. Disconnect the supply line from the tank by unscrewing the coupling nut at the bottom of the tank. Unbolt the toilet from the floor by removing the plastic caps at the base of the bowl and unscrewing the nuts on the closet bolts below.
The toilet lifts straight up from the wax ring and floor bolts. Have assistance for this step — a standard toilet weighs 60–100 pounds, and a two-person lift prevents the awkward single-person struggle that often causes the toilet to tip or contact surfaces with the wax ring still on it. Set the toilet outside the bathroom on cardboard or a tarp immediately after removal.
Flange Inspection and Wax Ring Installation
With the old toilet removed, inspect the flange (the ring at the floor that the toilet mounts to): it should be intact, at or slightly above floor level, and the closet bolts should be in good condition. A cracked flange or one that’s below floor level requires repair or replacement before the new toilet is installed — a leaking flange allows sewer gas and potentially sewage to enter the space below the floor.
Place a new wax ring on the bottom of the toilet horn (the circular projection on the toilet’s base that connects to the flange) or on the flange itself (either approach works; placing it on the toilet horn allows you to see the alignment as you set the toilet). The wax ring should be room temperature or slightly warm — cold wax doesn’t compress and seal properly. Set the toilet down onto the flange, guiding the closet bolts through the base holes, and press firmly and evenly to compress the wax ring fully.
Final Assembly and Leak Testing
Thread the washers and nuts onto the closet bolts and tighten evenly, alternating sides, until the toilet base sits firmly on the floor without rocking — do not overtighten, which can crack the porcelain base. Snap the plastic caps over the bolt stubs (they snap onto the plastic snap caps that come with most toilet sets). Reconnect the supply line to the tank fill valve.
Turn the water supply back on slowly and allow the tank to fill. Check all connection points for drips while the tank fills: the supply line connections at both the shutoff valve and the tank, and the base of the toilet where it meets the floor. Flush several times and watch the base during and after flushing for any water weeping out from under the base — a sign that the wax ring didn’t seal completely and the toilet needs to be reset.