Replace a Toilet

Goal

Remove an existing toilet and install a replacement on the same flange. Standard 2-hour residential job; the work isn't technically difficult but rushing the wax-ring seating is the #1 cause of callback leaks.

Prerequisites

• Replacement toilet (verify rough-in dimension: 12" most common, 10" or 14" in older homes)
• Wax ring (regular for standard flanges, extra-thick for flanges below floor level) OR rubber/foam waxless gasket
• New supply line (flexible braided, ⅜" comp x ⅞" BC)
• New closet bolts + cap kit (don't reuse old ones)
• Adjustable wrench, socket set, putty knife, towels
• Caulk (silicone, color-matched to floor)
• 90 - 120 minutes for a standard swap

Steps

1. Shut off the supply at the angle stop under the toilet.
2. Flush + drain the tank fully. Sponge out the remaining tank + bowl water; use a wet-vac for the trap water.
3. Disconnect supply line at the tank inlet.
4. Remove the closet-bolt nuts at the toilet base. Cut bolts with a sawzall if rusted.
5. Rock the toilet to break the wax seal, then lift straight up. Drag-lift can dump wax onto the floor - lift, don't slide.
6. Plug the drain immediately with a rag to prevent sewer gas during the rest of the install.
7. Scrape the old wax off the flange. A putty knife + paper towels gets most of it.
8. Inspect the flange. A broken or sunken flange = the install can't proceed without flange repair (flange extender, replacement, or a Twist-N-Set repair kit). Don't fight a bad flange with extra wax - it WILL leak.
9. Install new closet bolts. Position them at 3 and 9 o'clock relative to the flange opening.
10. Place the wax ring. Press onto the underside of the new toilet's outlet horn, or onto the flange - manufacturer preference varies. Don't pre-deform it.
11. Remove the rag plug from the drain.
12. Lower the toilet straight down onto the bolts. Sit on the toilet with full body weight to seat the wax. NO rocking; one firm press.
13. Hand-tighten the nuts, alternating sides to keep the toilet level. STOP when the toilet is firmly seated; over-tightening cracks the porcelain.
14. Check level in both directions. Shim with plastic shims if needed. Don't trim shims until final.
15. Install the supply line - use a wrench to snug, not gorilla-strength.
16. Open the supply slowly while watching the connections at the tank and the angle stop. Watch the floor around the base for the first 5 minutes.
17. Flush 3 times. Watch the base for any seepage between flushes.
18. Trim shims, caulk the base. Caulk continuously around the front + sides; leave a 1 - 2" gap at the BACK so any future leak is visible.
19. Cap the closet bolts. Reinstall the seat (often included separately).

Verification

• Toilet level both directions
• No wobble when seated on
• No leaks at supply, tank, or base after 3 flush cycles
• Wax-ring seal verified visually (no wax visible squeezing out the sides)
• Caulk neat around base except the rear gap

Troubleshooting

• Slow leak at the base after install: wax seal didn't seat. Pull the toilet, replace the wax, reseat. Don't keep tightening the bolts - that cracks the bowl.
• Toilet rocks after install: shim correctly. Plastic shims, level both directions, trim flush.
• Slow refill or weak flush: open the supply fully (a partially-closed angle stop is the most common cause), check the fill valve adjustment.
• Sewer smell after install: incomplete wax seal OR a missing/dry trap somewhere else in the home. Inspect the wax seal first.

References

• IAPMO Uniform Plumbing Code, Chapter 4 (Plumbing Fixtures)
• Manufacturer install instructions for the specific toilet