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How to Replace a Toilet Seat

This Old House plumbing and heating expert Richard Trethewey shows us how to replace a toilet seat, explaining the standard shapes of seats and the potential problems a DIYer might encounter.

Plumbing and heating expert Richard Trethewey puts the mystery behind toilet seat replacements to rest. Richard shows host Kevin O’Connor how simple toilet seat replacements have become, with standard sizes and bolt patterns. He even explains how corrosion-free plastic hardware is very easy to work with during installation.

Toilet Seat Standards

Toilet seats come in two standard varieties: oval and round. All oval toilet seats will fit oval toilets, and all-round seats fit round toilets. The spacing of the bolts that hold these seats to the toilet are also standard, so the only consideration to think of is the shape of the toilet.

How to Replace a Toilet Seat

  1. There are two caps on the back of the toilet seat on either side. Use a flat screwdriver to pop these caps off to gain access to the bolt.
  2. Look underneath the toilet seat and find the plastic nuts holding the seat in place. Use the pliers to get a grip on one of the nuts. There’s no need to squeeze too tightly; medium pressure will do.
  3. Return to the top of the toilet and use the widest screwdriver possible to loosen the bolt while still holding the nut underneath. The nut will usually loosen easily after the first few turns, so the pliers may become unnecessary.
  4. Repeat the process on the other bolt. Pull up on the toilet seat to remove it.
  5. Place the new toilet seat on the toilet, and pass the bolts through the holes. Many seats have plastic barbs to help keep the bracket in place. Push them through the bolt holes as well.
  6. Place the new plastic nut on the bolt and thread it on by hand. Once snug, tighten the bolt with the screwdriver, but do not over-tighten.
  7. Repeat the process on the other side and press the plastic caps down over the bolts.

How to Remove Corroded Toilet Seat Bolts

  1. Older toilet seat bolts and nuts were metal, and they could fuse together due to corrosion from moisture and urine. Here’s how to remove them.
  2. Place a piece of duct tape on the toilet to protect it.
  3. Lay a putty knife on the tape and hold it flat against the toilet.
  4. Pass the hacksaw back and forth to cut through the plastic hinge and eventually through the bolt.
  5. Remove the toilet seat and tap the cut bolt through the toilet.


Richard demonstrates how to replace an old or damaged toilet seat. When installing a new seat the first step is to determine what size toilet seat you need, be sure to use the right size seat to match the existing toilet.