Adjustable wrench
Use it for: To loosen and tighten the tank bolts and supply line nut.
Shop adjustable wrenchesToilet repair
How to Replace a Toilet Tank to Bowl Bolt Set
If your toilet leaks only when you flush and the water shows up between the tank and bowl, replacing the toilet tank to bowl bolt set is a common fix.
This repair is mostly about draining the tank, removing the old hardware, and tightening the new bolts evenly so the tank seals without cracking. Work slowly and do not force the porcelain.
Before you start: Match the replacement part to your exact toilet before ordering.
Safety first
- Porcelain cracks easily, so tighten tank bolts in small, even turns.
- Keep one hand on the tank when hardware is loose so it does not shift suddenly.
- Use towels or a bucket to control spills and reduce slip risk on the bathroom floor.
Tools you may need
Large flat screwdriver
Use it for: To hold the bolt head inside the tank while you loosen the nut below.
Shop large flat screwdrivers
Sponge or small towel
Use it for: To soak up the last water left in the tank before removing the bolts.
Shop sponges and towels
Small bucket
Use it for: To catch leftover water and hold old hardware during removal.
Shop small buckets
Work gloves
Use it for: To protect your hands from sharp old hardware and tight spaces behind the toilet.
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Step-by-step fix
Step 1: Confirm the bolt set is the likely problem
- Look around the seam where the tank sits on the bowl.
- Flush the toilet and watch for fresh water dripping from the tank-to-bowl area or from the bolts underneath the tank.
- Wipe the area dry first so you can tell whether the leak starts during or right after a flush.
- Check that the water is not coming from the supply line, shutoff valve, fill valve, or a crack in the tank.
If it works: You confirmed the leak starts at the tank-to-bowl connection or around the tank bolts when the toilet flushes.
If it doesn’t: If the leak comes from the supply line or another tank part, fix that part instead before removing the tank bolts.
Stop if:
- You find a visible crack in the tank or bowl.
- The toilet rocks badly or the bowl itself is loose at the floor.
Step 2: Shut off water and drain the tank
- Turn the toilet shutoff valve clockwise until the water stops.
- Flush the toilet and hold the handle down to drain as much water from the tank as possible.
- Use a sponge or towel to remove the remaining water from the bottom of the tank.
- Place a bucket and towel under the tank area to catch drips when the bolts come out.
If it works: The tank is mostly empty and safe to work on without spilling much water.
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 the water supply.
Step 3: Remove the old tank bolts
- Disconnect the water supply line from the bottom of the tank if it blocks access.
- From underneath the tank, loosen the nuts on the old tank bolts while holding the bolt heads inside the tank with a screwdriver.
- Remove the old nuts, washers, and bolts.
- Lift the tank straight up just enough to free the old hardware if needed, then set it down carefully in place or on a protected surface.
- Clean mineral buildup and old rubber residue from the bolt holes and the contact area around them.
If it works: The old bolt set is out and the bolt holes are clean enough for the new hardware to seal.
If it doesn’t: If the nuts are badly rusted, apply steady pressure and work them loose slowly rather than twisting hard against the porcelain.
Stop if:
- A bolt spins in damaged porcelain and the hole looks chipped or enlarged.
- The tank feels unstable enough that it may slip or fall while you are removing hardware.
Step 4: Install the new toilet tank to bowl bolt set
- Compare the new hardware to the old set so you understand the order of the pieces.
- Install each new bolt with its sealing washer inside the tank as the replacement set is designed to sit.
- Guide the bolts through the tank holes and into the bowl mounting holes.
- Thread the washers and nuts on by hand underneath so both sides start evenly.
- Tighten each side a little at a time, alternating left and right so the tank lowers evenly onto the bowl.
- Stop tightening when the tank feels secure and level. Do not crank down hard on one side.
If it works: The new bolt set is installed and the tank sits evenly on the bowl without wobbling.
If it doesn’t: If the tank leans or one side pulls down farther than the other, loosen both sides slightly and retighten evenly.
Stop if:
- You hear porcelain creaking, popping, or cracking while tightening.
- The tank will not sit evenly because the mounting surfaces are damaged.
Step 5: Reconnect water and check for leaks
- Reconnect the water supply line if you removed it.
- Turn the shutoff valve back on slowly and let the tank fill.
- Watch the bolt holes, the underside of the tank, and the seam between the tank and bowl as the tank fills.
- Dry the area with a towel, then flush once and watch again for fresh drips.
- If needed, snug each nut just a little more, alternating sides and checking after each small adjustment.
If it works: The tank fills and flushes without water dripping from the bolts or the tank-to-bowl connection.
If it doesn’t: If a small drip remains, make another very small, even adjustment on both sides. If the leak continues, recheck washer placement and part fit.
Stop if:
- Water leaks from a crack rather than from the bolt area.
- Tightening enough to stop the leak would clearly risk cracking the tank.
Step 6: Make sure the repair holds in normal use
- Flush the toilet several times over the next few minutes.
- Check the floor under the tank and the back of the bowl for any new water.
- Press gently on the tank to make sure it feels secure and does not shift.
- Recheck the area again later after the toilet has been used normally.
If it works: The toilet stays dry through repeated flushes and the tank remains secure.
If it doesn’t: If water returns only after several flushes, inspect the bolt set and the tank-to-bowl seal again to make sure everything is seated correctly.
Stop if:
- The leak returns quickly even though the new hardware is installed correctly.
- The tank loosens again, suggesting damaged porcelain or another failed sealing part.
Replacement Parts
Find a toilet tank to bowl 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 tank sits level on the bowl and does not rock when pressed gently.
- No water appears around the bolt heads, under the tank, or on the floor after several flushes.
- The bolts feel snug, but the porcelain is not under obvious strain.
- The toilet works normally in real use later the same day without a returning leak.
FAQ
Do I need to replace both tank bolts if only one is leaking?
Yes. Replace the full toilet tank to bowl bolt set so both sides seal and tighten evenly. Mixing old and new hardware often leads to another leak.
How tight should toilet tank bolts be?
Tight enough to hold the tank steady and stop leaks, but not so tight that the porcelain is stressed. Tighten each side a little at a time and keep the tank level.
Why does my toilet leak only when I flush?
That usually means water is escaping from the tank while it empties, often at the tank-to-bowl bolts or the seal between the tank and bowl.
Can I reuse the old washers or nuts?
It is better not to. Old rubber washers flatten out and old metal hardware may be corroded, which can keep the new repair from sealing well.
What if replacing the bolt set does not stop the leak?
The tank-to-bowl gasket may also be worn, or the tank or bowl may be cracked. Recheck the exact leak point before replacing more parts.