Symptoms
- Toilet shifts or rocks when you sit or stand
- Caulk around the base is cracked
- Bolt caps at the base are missing or loose
- Slight gap opens between toilet and floor on one side
Likely causes
- CommonLoose base (closet) boltsThe nuts holding the toilet to the floor flange have loosened over time or were never fully tightened.
- PossibleUneven or damaged flooring under the toiletA soft or uneven subfloor keeps the toilet from sitting flat even with tight bolts.
- PossibleBroken or corroded flangeA cracked or rusted floor flange can't hold the toilet steady no matter how tight the bolts are.
- PossibleOld, compressed wax ringA thin or unevenly compressed wax ring leaves a slight gap that lets the toilet rock.
What to do
- Pry off the plastic caps at the base to expose the bolts and nuts.
- Tighten each nut a little at a time, alternating sides, snugging evenly rather than cranking one side down first.
- Stop tightening once the toilet feels solid; overtightening can crack the porcelain base.
- If it still rocks after tightening, check for a gap under the base on one side using a flashlight.
- Slide plastic toilet shims into any gap to level it, then trim flush with a utility knife.
- Re-caulk around the base after shimming to keep it stable and prevent water from getting underneath.
- If the flange looks cracked or sits too low, plan on a plumber replacing it along with the wax ring.
Tools and parts
- Adjustable wrench or basin wrench
- Flashlight
- Toilet shims
- Caulk and caulk gun
Toilet floor shimsSearch: “plastic toilet leveling shims”
When to call a pro
Call a plumber if tightening the bolts doesn't stop the rocking, since the flange may be broken and need replacement.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.