Why is my toilet sloped or rocking and how do I fix it?

The floor is not flat. Tile, vinyl and concrete floors are rarely perfectly level. American Standard says a bowl that sits on a floor may not sit completely flat, and that its bowls have a built-in tolerance of up to 1/8 inch to allow for the variety of bathroom floor types. That is one maker's figure for its own bowls, but it shows that a tiny gap is expected. A bowl that clearly rocks is more than that. If the toilet leans to one side instead of rocking, suspect the floor first. Korky says if your floor is not level, use shims to make the toilet sit flat.

The bolts are loose. The floor bolts, also called closet bolts, hold the base down. Over time they can work loose, and American Standard's first suggestion for a slight rock is to "retighten the bowl-to-floor knobs."

The wax ring has failed. The seal closes the joint between the toilet and the drain. A toilet that moves works that seal loose, and a failed seal can let water and sewer gas out at the base. Our guide on why a toilet leaks at the base explains the signs of a failed ring.

The flange is damaged or at the wrong height. The flange is the ring on the drain pipe that the toilet bolts to. Korky says "you must get a replacement if your closet flange is cracked or damaged." If the flange sits too low or too high, the toilet cannot rest on the floor and seal at the same time. Korky's guidance for its wax-free seal shows how much this matters, since the seal you need depends on whether the flange is above, even with or below the finished floor.

The plumbing code expects the toilet to be held firmly. The 2024 International Plumbing Code says the flange "shall be attached to the drain and anchored to the structure." It also says floor outlet fixtures "shall be secured to the floor or floor flanges by screws or bolts of corrosion-resistant material." A toilet that rocks is not secured the way the code intends.

Try these steps in order, and stop when the toilet no longer moves.

1. 1Retighten the nuts. Alternate from side to side. Korky says to tighten "by alternating sides until the toilet becomes stable," and warns that overtightening the bolts "can cause the porcelain to crack."
2. 2Add shims. American Standard suggests toilet shims to stabilize the bowl. Korky also recommends shims when the floor is not level. Slide them into the gap under the base until the bowl stops rocking, and check that the toilet is stable from every side.
3. 3Watch for leaks afterward. Flush a few times and look around the base. If you see any water, the seal is compromised and the toilet needs to come up.

Caulk is where the two makers differ. American Standard suggests "a bead of caulk around the front base of the toilet for additional stability." Korky says "we do not recommend using caulk around the base," because if there is a leak, caulk will make it go unnoticed. Korky adds that if you do use caulk, you should leave the back uncaulked so water has a path to escape. If you use any at all, keep it to the front and leave a gap at the back so a leak can show.

Shims and caulk should not be used to hide a leak. If water is coming out at the base, fix the seal.

If shims do not settle the toilet, or you see water or smell sewer gas, the toilet needs to come up. Korky's steps for fixing a wobbling toilet are:

1. 1Shut off the water and empty the tank. Turn off the supply, flush, and hold the handle down to drain the tank. Get out as much water from the tank and bowl as you can.
2. 2Disconnect the supply line. Once the tank is empty, disconnect the water supply from the toilet. If the line or shut-off valve is old, see how to replace a toilet supply line and how to replace a toilet shut-off valve.
3. 3Remove the nuts, bolts and washers, then lift the toilet. Toilets are heavy, and Korky recommends having help. If you are alone, Korky suggests removing the tank from the bowl first.
4. 4Clean the flange. Use a putty or utility knife to remove the old wax ring, and remove as much residue as you can from the top of the flange. Korky suggests stuffing a rag into the drain pipe hole so sewer gas does not come up and nothing falls in.
5. 5Inspect the flange. Look for cracks or damage. Korky says if you notice cracks or damage, "you must replace it with a new flange," and that it does not recommend using sealants when the flange is cracked. See how to fix a broken toilet flange.
6. 6Test-fit the toilet without a seal. Korky says to place the toilet on the flange without a seal to make sure it will sit flat, and to use shims if the floor is not level.
7. 7Measure the flange height. This decides which seal and how many rings you need.
8. 8Set the toilet on a new seal. Korky's guide covers a wax-free seal with foam rings. It says to use the thin foam ring if the flange is 1/2 inch or more above the finished floor, the thick ring if it is less than 1/2 inch above, and both rings if the flange is even with the floor. If the flange is 3/8 inch or more below the finished floor, it says to stack two full seals and that you may need longer bolts. Those numbers apply to Korky's seal, so follow the instructions that come with whichever seal you buy.
9. 9Tighten evenly. Alternate sides and press down on the bowl to compress the seal. Korky says a wax-free seal is repositionable and lets you make more than one attempt, while it warns that a wax seal is ruined if the toilet is not set correctly on the first try.
10. 10Reconnect the water, and test. Turn the water on slowly, watch the base while the tank fills, and flush several times.

Call a plumber if you find any of these:

• The flange is cracked, rusted or loose, or it sits at a height the seal cannot handle.
• Water or a sewer smell keeps coming back after you reset the toilet.
• The toilet rocks again soon after you reset it, which can mean the flange is not anchored to the floor.
• The floor around the toilet gives way underfoot or looks damaged. Do not shim a problem you have not found.

A reset takes some lifting and a clean seat for the new seal. If you would rather not do it yourself, HQ Plumbing and Air's toilet repair team can reset the toilet, repair the flange and check the drain. We are licensed and insured, and you get the price up front. If you are thinking the toilet itself may be the problem, see how to know when to replace a toilet. If only the seat moves and the porcelain stays put, the fix is different, and how to tighten a wobbly toilet seat walks through it.

A rocking toilet is one of the most common bathroom plumbing mistakes.