Step-by-step fix
Step 1: Confirm the tank bolts are the leak source
- Dry the outside of the tank, the underside of the tank near the bolts, and the back edge of the bowl.
- Flush once, then watch closely where fresh water appears.
- Look for drips forming at the tank bolts or running down from the bolt holes under the tank.
- Check that the leak is not starting higher up at the fill valve, supply line, or from a crack in the tank.
If it works: You have confirmed the leak is coming from one or both tank bolts or their washers.
If it doesn’t: If the water starts at the center flush valve opening, the tank-to-bowl gasket or flush valve seal is a better repair path. If the water starts at the supply connection, address that connection instead.
Stop if:- You find a crack in the tank or bowl.
- The toilet rocks badly or the tank feels unstable enough that it may break during removal.
Step 2: Shut off water and empty the tank
- Turn the toilet shutoff valve clockwise until it stops.
- Flush the toilet and hold the handle down to drain as much water from the tank as possible.
- Use a sponge or towels to remove the remaining water from the bottom of the tank.
- Place a bucket or pan under the tank area to catch drips while you work.
If it works: The tank is mostly empty and safe to work on without constant dripping.
If it doesn’t: If the shutoff valve does not fully stop the water, close the home's nearest working fixture valve only if you know the plumbing layout, or wait until you can replace the shutoff before continuing.
Stop if:- The shutoff valve leaks heavily when turned.
- The valve will not close and water keeps refilling the tank fast enough to prevent safe work.
Step 3: Remove the old bolts and washers
- From inside the tank, hold the bolt head steady with a screwdriver.
- From underneath the tank, loosen the nut with an adjustable wrench.
- Repeat for the second bolt, supporting the tank with one hand as the hardware comes free.
- If the nuts are badly rusted, apply steady pressure first. If they still will not move, carefully cut the old bolts with a mini hacksaw.
- Lift out the old bolts and washers and remove any leftover rubber or corrosion from the bolt holes.
If it works: The old tank bolts and washers are out, and the bolt holes are clean enough for the new parts to seat flat.
If it doesn’t: If the hardware is fused in place, cutting the old bolts is usually faster and safer than forcing them until the porcelain is stressed.
Stop if:- The porcelain around a bolt hole is chipped through, cracked, or crumbling.
- The tank shifts in a way that makes it hard to control safely while removing the last fastener.
Step 4: Install the new toilet tank bolt set with washers
- Compare the new parts to the old ones so you understand the order before installing them.
- Insert each new bolt through its rubber washer and place it through the tank hole from inside the tank.
- Install the matching washer and nut underneath in the order provided with the replacement set.
- Tighten each side a little at a time so the pressure stays even from left to right.
- Snug the hardware until the rubber washers compress and the tank feels secure, but do not overtighten porcelain.
If it works: Both new bolts and washers are installed evenly, and the tank sits securely without obvious twisting.
If it doesn’t: If the tank looks crooked, loosen both sides slightly and retighten in small alternating turns until it sits evenly.
Stop if:- A bolt keeps spinning because the parts are assembled in the wrong order and will not seat.
- You hear porcelain creaking or see the tank start to stress while tightening.
Step 5: Refill the tank and check for leaks
- Turn the shutoff valve back on slowly and let the tank fill.
- Watch the bolt heads inside the tank and the nuts underneath as the water level rises.
- Dry the area again and wait a few minutes to see whether any fresh moisture forms.
- If needed, tighten each side just a little more, alternating side to side.
If it works: The tank fills and stays dry around both bolts and washers.
If it doesn’t: If a slow drip continues, recheck the washer placement and make sure both sides are tightened evenly. If the leak still does not stop, the tank-to-bowl gasket or the tank itself may also be involved.
Stop if:- Water begins leaking from a new crack or from a different fitting you disturbed during the repair.
Step 6: Test the repair in normal use
- Flush the toilet several times and watch underneath the tank after each flush.
- Run a dry paper towel around the bolt nuts and the back rim of the bowl to catch small drips.
- Check again after 15 to 30 minutes to make sure no slow seepage returns.
- Wipe up the area and remove your bucket or towels once everything stays dry.
If it works: The toilet flushes normally and the tank bolt area stays dry during and after real use.
If it doesn’t: If moisture returns only after flushing, revisit the bolt tension and washer seating. If the area stays dry at the bolts but leaks elsewhere, move to the actual leak source instead of tightening further.
Stop if:- The tank shifts on the bowl during flushing or feels loose enough to risk breakage.
Replacement Parts
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FAQ
Do I need to replace both tank bolts if only one is leaking?
Yes. Replace both bolts and washers as a set. If one side has worn out or rusted, the other side is usually not far behind, and even tightening is easier with matching new parts.
How tight should toilet tank bolts be?
Tight enough to compress the rubber washers and hold the tank steady, but not so tight that the porcelain is stressed. Tighten a little on each side, alternating back and forth.
Can I reuse the old washers if they still look okay?
It is better not to. Old rubber can harden, flatten, or crack once disturbed. New washers are cheap insurance against doing the job twice.
What if the old bolts are badly rusted and will not come off?
Cutting them off carefully with a small hacksaw is often the safest option. Forcing seized hardware can twist the tank or crack the porcelain.
Will replacing the tank bolts fix every leak between the tank and bowl?
No. If water is leaking from the center of the tank-to-bowl connection, the tank-to-bowl gasket or flush valve area may be the real cause. Confirm the leak source before replacing parts.