What toilet bowl bolts are and why they fail

Toilet bowl bolts are the two fasteners that anchor your toilet to the floor flange — the ring-shaped fitting that connects your toilet drain to the waste line below. Over time, these bolts corrode from moisture and mineral deposits, crack from the weight of the toilet, or straightforward loosen until they no longer hold the bowl in place. A wobbly toilet is the first sign they need replacing.

The bolts themselves are usually brass or stainless steel, about 1/4 inch in diameter and 2 to 3 inches long. They sit inside the bolt holes on either side of the toilet base, hidden under plastic caps. When they fail, water can seep between the toilet and the floor, rotting the subfloor and creating a much larger repair job. Replacing them is a straightforward task that takes 30 to 45 minutes and costs $10 to $30 in parts.

Key Takeaways

  • Toilet bowl bolts anchor the toilet to the floor flange and corrode or crack over time, causing the toilet to rock or leak at the base.
  • You will need a wrench, a screwdriver, a putty knife, and a new bolt kit (usually two bolts, washers, and nuts) from any hardware store.
  • The job requires turning off the water, draining the tank and bowl, and removing the old bolts from underneath the toilet base before installing new ones.
  • If the bolts are seized or the flange is cracked, you may need to call a plumber rather than force the old hardware out.

Gather your tools and materials

Before you start, turn off the water supply to the toilet. The shutoff valve is usually on the wall or floor behind the toilet. Turn the handle clockwise until it stops. Flush the toilet to empty the tank, then hold the handle down for a few seconds to drain the bowl as much as possible.

You will need an adjustable wrench or a socket wrench that fits the bolt nuts (usually 1/2 inch), a flathead screwdriver, a putty knife, and a new toilet bowl bolt kit. These kits are sold at any hardware store and include two bolts, washers, and nuts. Some kits also include rubber seals or wax rings, which you may or may not need depending on whether you are replacing the wax ring at the same time. If the old bolts are very tight, a penetrating oil like WD-40 can help loosen them.

Remove the plastic caps and access the bolts

The bolt nuts are hidden under plastic caps at the base of the toilet on both sides. Pry these caps off gently with a flathead screwdriver or putty knife. They usually pop off without much force. Once the caps are off, you will see the bolt nuts and washers underneath.

Look at the condition of the bolts before you try to remove them. If they are visibly corroded or the nuts are stuck, spray them with penetrating oil and wait 10 to 15 minutes. This makes them much easier to turn and reduces the risk of stripping the nut or breaking the bolt.

Loosen and remove the old bolts

Using your wrench, turn the nut on the first bolt counterclockwise. Turn slowly and steadily. If the nut is very tight, do not force it — stop and explore more penetrating oil, wait another 10 minutes, and try again. Forcing a corroded nut can snap the bolt or strip the threads, which makes removal much harder.

Once the nut is loose, unscrew it by hand and remove the washer. You may see a rubber seal or gasket under the washer; keep it if it is still in good condition, or replace it if it is cracked or flattened. Now reach under the toilet base from inside the bowl and push the bolt up and out. It should slide out easily once the nut is off. Repeat this process for the second bolt on the other side.

Install the new bolts

Before you insert the new bolts, inspect the floor flange for cracks or damage. If the flange is cracked or broken, the new bolts will not hold the toilet securely, and you should call a plumber to replace the flange. If the flange looks solid, proceed with installing the new bolts.

Insert the first new bolt into the bolt hole from underneath the toilet base, pushing it up through the hole until the head of the bolt sits against the flange. The bolt should slide in smoothly. If it does not, the flange may be misaligned or damaged. Slide the washer onto the bolt, then thread the nut onto the bolt by hand. Do not tighten it yet.

Repeat this process for the second bolt on the other side. Once both bolts are in place with washers and nuts hand-tightened, you can tighten them with your wrench. Tighten each bolt a little at a time, alternating between the two sides, until the toilet is snug against the floor. Do not over-tighten — the goal is to stop the rocking, not to crush the porcelain or the flange.

Test the toilet and replace the caps

Once both bolts are tightened, rock the toilet gently from side to side. It should not move. If it still rocks, tighten the bolts a bit more, alternating between the two sides. Once the toilet is stable, turn the water supply back on and let the tank fill. Flush a few times and check under the base for any leaks.

If water is leaking from under the toilet base, the wax ring may be damaged or the bolts may not be tight enough. Tighten the bolts another quarter turn on each side and test again. If the leak continues, you may need to remove the toilet and replace the wax ring — a separate job that takes about an hour.

Once you are satisfied the toilet is find and not leaking, snap the plastic caps back onto the bolts. They should click into place. You are done.

When to call a plumber instead

If the old bolts are seized and will not budge even after soaking with penetrating oil, do not keep forcing them. Excessive force can crack the flange or snap the bolt, making the job much more expensive. A plumber has specialized tools to remove stuck bolts without damaging the flange.

If the floor around the toilet base is soft or spongy, the subfloor has rotted and needs repair before you replace the bolts. If the floor flange is cracked, broken, or sitting below the floor level, it must be replaced — another job for a plumber. If you are unsure whether the flange is damaged, take a photo and show it to a plumber before you start.

Frequently Asked Questions

Can I replace just one bolt, or do I have to replace both?

Replace both bolts at the same time. Even if only one is corroded, the other is likely to fail soon, and you will have to do the job again in a few months. Replacing both takes only a little longer and saves you the trouble of repeating the work.

What size bolts does my toilet need?

Most toilets use 1/4-inch bolts that are 2 to 3 inches long. Bring the old bolt to the hardware store if you are unsure, or look at the bolt kit packaging — it will say the size. Toilet bolt kits are standardized, so any kit labeled for toilet bowl bolts will fit your toilet.

Do I need to replace the wax ring when I replace the bolts?

Not necessarily. If the toilet is not leaking and the wax ring looks intact, you can leave it alone. If water is already leaking from under the base, or if the wax ring is cracked or flattened, replace it at the same time. Replacing the wax ring requires removing the toilet, so it is worth doing both jobs together if the ring is damaged.

How tight should the bolts be?

Tighten them until the toilet stops rocking and sits flat on the floor. You should not be able to move the toilet side to side by hand. Over-tightening can crack the porcelain or the flange, so stop once the toilet is stable. If you hear cracking sounds while tightening, stop when ready and loosen the bolts slightly.

What if water leaks from under the toilet after I replace the bolts?

First, tighten the bolts another quarter turn on each side and test again. If the leak continues, the wax ring is likely damaged and needs replacement. This requires removing the toilet, which is a separate job. If you are not comfortable doing this yourself, call a plumber.