How do you stop toilet tank bolts from leaking?

To stop toilet tank bolts from leaking, you need to address improper installation, worn components, or loose fittings—these are the most common causes of leaks around tank - to - bowl bolts. Follow these step - by - step solutions:

1. Inspect and Replace Worn Washers/Gaskets

Tank bolts rely on rubber washers to create a watertight seal. Over time, these washers harden, crack, or compress, leading to leaks.

• What to do:

a. Turn off the water supply valve to the toilet and flush to empty the tank.

b. Remove the bolt nuts from the underside of the bowl (use a wrench, but avoid over - tightening).

c. Take out the old washers—there should be two washers per bolt: one inside the tank (under the bolt head) and one outside (between the bowl and the nut).

d. Replace them with matching - size rubber or neoprene washers (5/16" is the standard size for most residential toilets; refer to the previous size guide). Neoprene washers are more durable than standard rubber.

2. Tighten Bolts Evenly (Avoid Over - Tightening)

Loose bolts cause gaps between the tank and bowl, while over - tightening can crack the ceramic tank or bowl—both lead to leaks.

• What to do:

a. After replacing washers, reattach the tank to the bowl and hand - tighten the nuts first to align the tank properly.

b. Use a wrench to tighten each nut a quarter turn at a time, alternating between bolts (like tightening a car wheel lug nut). This ensures even pressure across the tank base.

c. Stop as soon as resistance is felt—do not force the wrench.

3. Use a Tank - to - Bowl Gasket (Main Seal Check)

Sometimes, leaks around bolts are mistaken for a failed main tank - to - bowl gasket (the large rubber seal between the tank outlet and bowl inlet). If the gasket is worn, water can seep around the bolts.

• What to do:

a. While the tank is removed, inspect the main gasket for cracks, tears, or misalignment.

b. Replace it with a gasket that matches your flush valve size (2 - inch for standard toilets, 3 - inch for high - efficiency models).

c. Ensure the gasket is seated evenly in the tank outlet groove before reattaching the tank.

4. Apply Thread Sealant (Optional for Persistent Leaks)

For stubborn leaks, use a non - corrosive thread sealant tape or paste (PTFE tape is ideal) on the bolt threads—this helps seal minor gaps between the bolt and nut.

• Note: Do not use too much sealant, as excess can squeeze out and clog the flush valve.

5. Replace Corroded Bolts

Rust or corrosion on steel bolts can break the seal and damage washers.

• What to do: Replace steel bolts with stainless steel or brass bolts—they resist corrosion and last longer. Universal toilet tank bolt kits (including bolts, washers, and nuts) are available at hardware stores.

Final Check

After reassembly, turn the water supply back on, fill the tank, and check for leaks around the bolt nuts and tank base. Wipe the area with a dry paper towel to spot small drips easily.