Toilet Tank Leaking From Bolts-Causes & Fixes

Leaky toilet tank bolts is a problem you’ve probably encountered or you are likely to deal with in the future, especially if you have an old 2-piece toilet. Though common in tanks that have been in use for a long time, it can also happen in newly installed units.

Your toilet is leaking from tank bolts because of corroded, damaged, loose or misaligned washers and bolts. The solution is to either tighten or replace the tank bolts. You might also want to check the bowl gasket.

Read on for more details on causes and fixes. In addition, find answers to frequently asked questions, including why there are leaks when flushed only and in brand new tanks of different toilet brands.

Why Toilet Tank is Leaking from Bolts + Fixes

Damaged Washers

When you buy a 2-piece toilet, the tank and bowl are separate pieces. During installation, you attach the tank and the bowl with bolts, washers and gaskets. Following is a toilet-to-tank bolts diagram.

Toilet tank to bowl bolts diagram

The rubber washers go inside to stop water leaks inside the tank. Between the tank and the bowl goes a brass flat washer and brass nut to connect the toilet tank and bowl.

The additional washers and nuts are placed under the toilet bowl.

The rubber washers in your toilet’s tank bolts may wear out over time, causing the tank bolts to damage and eventually leak. Dripping water on the bolts and nuts, as well as the floor beneath them, shows the washers need replacement

How to Remove Damaged Washer

You need an adjustable wrench, as well as a set of bolts, nuts, and washers, to accomplish this task.

Follow the procedure below:

1. Empty the toilet tank of any remaining water.

To begin, make sure you turn off the water supply to the toilet by turning off the valve behind the toilet bowl. Flush the toilet to empty the bowl, then pull the water supply line of the tank clean with the adjustable wrench. By absorbing the residual water in the bowl with a sponge or a cloth, you can get rid of it.

2. Take off the tank’s lid.

Remove the lid from the toilet tank and place it on a pile of towels or blankets to make room for the tank.

3. Unbolt the nuts and bolts.

Loosen the nuts from the bolts with an adjustable wrench, and if they’re stuck, have a helper spin the bolts with a screwdriver from inside the tank while you hold the nut with the wrench. Apply penetrating oil to loosen the nuts from the bolts and free them from the bowl’s casing to make the job easier.

4. Remove the tank and place it on a cushioned surface.

When the tank is hefty, it is better to get the help of a friend to help you hoist it straight up and move it to the padded surface. For safety, lay it flat.

5. Replace any worn-out washers.

Extract the bolts from the toilet tank after completing the instructions above, making sure to remove all the old rubber washers.

This 2 Pack toilet tank to bowl bolt kit that includes heavy duty solid brass bolts with extra long + double gaskets

Brass bolts kit
Brass Kit

How to Replace Damaged Washers

Follow these instructions to install the replacement rubber washers:

  1. Place one rubber washer just under the bolt head on the bolt.
  2. Place the bolt into the bolthole of the tank.
  3. On the bolt on the outside of the tank, place the second rubber washer.
  4. Add the third rubber washer and a new bolt nut to the bolt.
  5. To fasten the tank to the toilet bowl housing, use a new metal washer.
  6. On the second bolt, replace the washers and nuts in the same order.
  7. Refill the toilet tank.
  8. Reposition the tank over the bowl housing and reinstall the central tank gasket and bolts. Fasten the bolts, then double-check that you connected the tank correctly and is perpendicular to the bowl’s casing. To refill the tank, reconnect the water supply and turn it back on, making sure that the cover is in place.
  9. After you accomplish all the work for a while, check the bolts for leaks; if there are any, you may need to repeat the process or get a professional to check it out.

You can repair leaking tank bolts by following these simple procedures. However, if you find that these methods aren’t working, it may be time to enlist the help of a professional.

Corroded or Damaged Tank Bolts

Hard water can cause corrosion in your tank bolts. Homeowners who live in areas with particularly hard water can prevent this by using solid brass bolts.


If you are using hard water, you can spray your bolts with a rust protector. This can help extend their life, hence preventing rust. Consider rust-resistant brass or stainless steel nuts and bolts

Stainless Steel bolts and nuts
Stainless steel bolts and nuts

If you have a toilet tank bolt that is damaged or corroded, you can just cut off the nut. This is easy to do with a mini hacksaw.

If the bolts just spin in circles instead of becoming loose, remove and replace them. To get them off, use a screwdriver on the head of the bolt and your wrench on the nut. Twist the wrench to the left. This should loosen them up.


  1. Turn off the water supply valve going to the tank.
  2. If you have a flap style flush fail, hold the handle down to empty the toilet tank. For a canister style pull the handle and hold it up.
  3. Then remove the tank cover
  4. Remove the supply line. You can put a container under it to catch any water,
  5. to disconnect the supply line and the fill valve.
  6. Remove all the necessary bolts, washers, and nuts from both the inside of the tank and below the bowl.
  7. Replace any faulty spacers, bolts and washers between the tank and the bowl.
  8. Now take the tank and gently place it onto the bowl.
  9. Ensure that you align the holes.
  10. Slip a bolt with a washer into each of the aligned holes.
  11. Continue to hold the tank in the right position and put a washer on the bolt and under the bowl.
  12. Tighten the nut. When you tighten the nut, start by tightening it with your hand, and then gently tighten it more with a tool. It is essential to be as careful as possible so that you do not crack the porcelain. Give the nuts a snug fitting.
  13. Turn the water back on and give your toilet a test flush.
  14. Check for any leaks.

Misaligned or Loose Bolts or Washers

The solution to this is simply to align and tighten the bolts.

  1. Hold the toilet in position
  2. Tighten the nut. When you tighten the nut, start by tightening it with your hand, and then gently tighten it more with a screwdriver or an adjustable wrench. It is essential to be as careful as possible so that you do not crack the porcelain. Give the nuts a snug fitting.
  3. Turn the water back on and give your toilet a test flush.
  4. Check for any leaks.

Damaged Bowl Gasket

The tank-to-bowl gasket can also become damaged due to corroded bolts or worn-out washers.

Toilet tank to bowl gasket
Bowl Gasket

The location of the gasket is where the tank connects to the bowl. It helps to create a seal between the toilet tank and the toilet bowl so that water can pass through the plumbing.

Replacing the tank to bowl gasket

Remove the old gasket and inspect it. If it looks worn or damaged, you’ll definitely want to replace it.

For replacing the gasket, follow the procedure below:

  1. Turn off the water supply valve going to the tank.
  2. If you have a flap-style flush fail, hold the handle down to empty the toilet tank. For a canister style pull the handle and hold it up.
  3. Then remove the tank cover
  4. Remove the supply line. You can put a container under it to catch any water
  5. Disconnect the supply line and the fill valve.
  6. Then remove the toilet, and you will see the old gasket.
  7. Remove it and replace it with a new one also replace the bolts.
  8. After this return the toilet and fix it in place with the new bolts and do not tighten them so much.
  9. Reconnect the supply line and the fill valve and turn the water back on.
  10. Flush the toilet to see if it is still leaking.

Toilet Leaking from Tank Bolts when Flushed

This can be due to loose or misaligned bolts and washers, especially in newly installed units. It can also happen shortly after the replacement of the bolts. Simply tighten the nuts as highlighted above.

Plumbers Putty for Leaky Toilet Tank Bolts?

The plumber’s putty is not intended to seal tank bolts. It may work as a temporary solution but is not a good idea in the long run.

Although it is a good sealant when used in the right places, it won’t provide a proper seal when it comes to tank bolts. Using a sealant can also break the watertight seal that the rubber washers and gaskets provide.

However, some plumbers suggest that you can silicone sealants under the following conditions.

  • The silicone should be spread fully across the bolt heads and onto the adjacent porcelain on the inside of the water closet or water tank. A thick layer over the rusty bolt heads should be a must to prevent the likelihood of any leakages from occurring.
  • The whole area where you apply the silicone should be clean and very dry. The silicone will not adhere well to wet surfaces.
  • You would need to apply the patch over the entire bolt head all in one go. A secondary application of the silicone will not adhere well to a cured first layer.
  • Make sure to let the silicone material fully cure before trying to put the water closet back into service.
  • Removal of the silicone from any surfaces that it decides to really stick to can be a pain to get it all off. This would be especially true for many toilet tanks that do not have a fully glazed interior. The best fix is to simply replace the bolts, the washers, and the tank to bowl gasket

Are Toilet Tank Bolts Universal?

Most tank-to-bowl repair kits come with universal bolt sizes that can fit bolt holes of different toilet tanks. However, custom toilets and some brands may require different sizes. Be sure the size you order matches what you already have.

It is important to carefully check the bolts you have before buying new ones for replacement.

Leaky Kohler &American Standard Toilet Tank Bolts

Be it, Kohler, American Standard, Mansfield, or any other 2pc toilet brand, damaged or misaligned bolts and washers are the major reasons your toilet, is leaking from the bolts. Check the solutions discussed above for details.

While there are universal tank-to-bowl bolts, Kohler and American Standard toilets have their own kits.

Kohler tank to bowl bolts repair kit
Kohler Kit
American Standard Toilet Tank Bolts
American Standard Bolts Kit

Why is my Toilet Tank still leaking after Replacing Bolts?

The nuts on the bolts may need to be tightened up. Leaks can also occur if you tighten the nuts too much as well. Ideally, they should be snug. Overly tight nuts can also damage the gasket and possibly crack the toilet bowl or the tank.

Moreover, the leaking of the toilet may not be caused by the bolts, it may be the gasket or even the Flapper.

Brand New Toilet Leaking from Tank Bolts-Why?

One reason for a toilet leak from a brand-new toilet might be a loose connection where the tank meets the toilet.

  1. Check the connecting bolts. If they seem loose, or you can see water gathering in that area, use the screwdriver to tighten them. Approach the bolts from inside the tank and screw them down to create the best seal.
  2. Dry the area and wait 15 minutes. If water gathers in the area, move on to replacing the bolts and washers.
  3. Shut off the water at the valve, then flush and hold the handle until all the water has drained from the tank.
  4. Remove the old bolts and washers.
  5. Clean and dry the area, then install new washers and bolts.
  6. Screw in place with the screwdriver/adjustable wrench
  7. Check for any leakage 

Toilet Leaks: Further Reading

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