Adjustable wrench
Use it for: To loosen and tighten the tank bolt nuts and water supply connection.
Shop adjustable wrenchesToilet repair
How to Replace a Toilet Tank Bolt Set
Replace the toilet tank bolt set when water is leaking from the bolts under the tank or from the tank-to-bowl connection and the old bolts or washers are corroded, loose, or no longer sealing.
This repair is straightforward if the tank and bowl are still in good shape. The main job is to remove the tank, install the new bolts and sealing washers correctly, then tighten everything evenly so the tank seals without cracking.
Before you start: Match the replacement part to your exact toilet before ordering.
Safety first
- Lift the tank carefully. Porcelain is heavy, slippery, and easy to crack if dropped or twisted.
- Tighten tank bolts evenly and in small steps. Over-tightening can crack the tank or bowl.
- Keep towels down around the base so leftover water does not make the floor slippery.
Tools you may need
Large flat screwdriver
Use it for: To hold the bolt heads inside the tank while you loosen or tighten the nuts below.
Shop flat screwdrivers
Sponge or small cup
Use it for: To remove the last bit of water from the tank before lifting it off.
Shop sponges for cleanup
Bucket or towels
Use it for: To catch leftover water and protect the floor around the toilet.
Shop towels and cleanup cloths
Penetrating oil
Use it for: To help free rusted or mineral-stuck nuts on older tank bolts.
Shop penetrating oilAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Step-by-step fix
Step 1: Make sure the tank bolt set is the real problem
- Dry the outside of the tank, the underside near the bolts, and the area where the tank meets the bowl.
- Flush the toilet and watch closely as the tank refills.
- Look for water forming around the tank bolts, dripping from the bolt nuts underneath, or seeping from the tank-to-bowl connection right after a flush.
- Check whether the bolts are visibly rusted, the rubber washers look flattened or cracked, or the nuts will not stay snug.
If it works: You confirmed the leak is coming from the tank bolts or their sealing washers.
If it doesn’t: If the leak is coming from the supply line, fill valve, flush valve, or a crack in the tank, fix that issue instead of replacing the tank bolt set.
Stop if:
- You find a visible crack in the tank or bowl.
- The toilet rocks badly or the bowl itself is damaged.
Step 2: Shut off the 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 small cup to remove the remaining water from the bottom of the tank.
- Place towels or a bucket under the tank area to catch drips when you disconnect parts.
If it works: The water is off and the tank is empty enough to remove safely.
If it doesn’t: If the shutoff valve does not fully stop the water, close the home's main water supply before continuing.
Stop if:
- The shutoff valve leaks heavily when you turn it.
- The valve will not close and you cannot safely stop water flow.
Step 3: Disconnect the tank and remove the old bolt set
- Disconnect the water supply line from the bottom of the tank.
- Loosen the nuts on the tank bolts underneath the tank while holding the bolt heads inside the tank with a screwdriver.
- If the nuts are stuck, apply penetrating oil and give it a few minutes to work.
- Lift the tank straight up and set it on a towel or protected surface.
- Remove the old bolts, rubber washers, metal washers, and nuts from the tank holes.
- Wipe the bolt holes and the sealing surfaces clean so the new parts can seat properly.
If it works: The tank is off and the old toilet tank bolt set has been removed.
If it doesn’t: If the nuts are badly seized, keep the tank supported and work them loose slowly rather than forcing the porcelain.
Stop if:
- A bolt spins in damaged porcelain or the tank starts to crack.
- The bolt holes are chipped enough that the new washers will not seat flat.
Step 4: Install the new bolts and washers in the tank
- Compare the new parts to the old set so you understand the order of the washers and nuts.
- Insert each new bolt with its rubber sealing washer on the inside of the tank so the rubber sits directly against the porcelain.
- Install the remaining washer and nut arrangement supplied with the set on the outside of the tank, if your kit uses them, and snug them enough to hold the bolts in place.
- Make sure both bolts sit straight and the rubber washers are centered over the holes.
If it works: The new bolts are installed in the tank and the sealing washers are seated flat.
If it doesn’t: If the hardware stack-up in your kit is unclear, pause and follow the included diagram so the rubber washer ends up sealing against the inside of the tank.
Stop if:
- The replacement bolts do not fit the tank holes or the hardware cannot seat squarely.
Step 5: Set the tank back on the bowl and tighten evenly
- Lower the tank onto the bowl carefully, guiding the bolts through the mounting holes.
- Install the washers and nuts underneath the bowl as provided in the kit.
- Tighten each side a little at a time, alternating left and right so the tank comes down evenly.
- Watch the gap and tank position as you tighten. The tank should stay level and stable without being forced.
- Reconnect the water supply line to the tank.
If it works: The tank is mounted securely and evenly with the new toilet tank bolt set in place.
If it doesn’t: If the tank looks crooked, loosen the nuts slightly, re-center the tank, and tighten again in small alternating turns.
Stop if:
- The porcelain creaks, shifts sharply, or shows any sign of cracking while tightening.
- The tank will not sit evenly because the bowl mounting surface is damaged.
Step 6: Refill the tank and confirm the repair holds
- Turn the shutoff valve back on slowly and let the tank fill.
- Dry the bolts, nuts, and the tank-to-bowl area again so any new leak is easy to spot.
- Flush several times and check underneath the tank after each flush.
- Run a hand or dry tissue around the bolt nuts and under the tank to confirm there is no fresh moisture.
- If needed, tighten each nut just a little more, alternating sides and avoiding over-tightening.
If it works: The toilet fills and flushes without leaking from the tank bolts or the tank-to-bowl connection.
If it doesn’t: If a small drip remains, recheck washer placement and tank alignment. If the leak continues after careful retightening, remove the tank and inspect for a damaged washer seat or hidden porcelain crack.
Stop if:
- A steady leak continues even with correct washer placement and light retightening.
- You discover a crack in the tank once it is refilled.
Replacement Parts
Find a toilet tank bolt set on Amazon
Match the replacement part to your exact toilet before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- The area under the tank stays dry through several flushes.
- The tank sits level and does not rock on the bowl.
- There is no fresh rust-colored drip or bead of water forming at either bolt.
- The shutoff valve and supply connection remain dry after the repair.
FAQ
Do I need to replace all the tank bolts if only one is leaking?
Yes. Replace the full toilet tank bolt set so both sides seal the same way and tighten evenly. Mixing old and new hardware often leads to another leak soon after.
Should I use sealant on toilet tank bolts?
Usually no. The rubber washers are meant to make the seal. Adding sealant can make the parts seat poorly and can hide the real cause of a leak.
How tight should toilet tank bolts be?
Tight enough to compress the washers and stop leaks, but not so tight that the porcelain is stressed. Tighten both sides gradually and evenly rather than cranking one side down at once.
Why is my toilet still leaking after I replaced the bolt set?
The most common reasons are washer placement in the wrong order, uneven tightening, a tank that is not sitting squarely, or a hairline crack in the tank. Dry everything and watch closely during a flush to pinpoint the source.
Can I reuse the old washers or nuts?
It is better not to. Old rubber washers are often flattened or brittle, and old metal hardware may be corroded. Using the full new set gives the best chance of a lasting seal.