Our Fix for the “Impossible” Case Toilet Seat

A few years ago, my dad—an engineer with a soft spot for vintage plumbing—ran into a familiar problem: the seat on our Case toilet had cracked, and nothing available today would fit it properly. The Case 1000 and 1100 models, known for their sleek one-piece “Lowboy” design and side-mounted tank levers, use an uncommon 7-inch bolt spacing with front-mount hardware. Standard toilet seats simply don’t line up. Original replacements, once expensive, were now nearly impossible to find—especially in matching colors.

Determined not to junk a perfectly good fixture, he sketched an adapter plate and began prototyping it on a 3D printer. We started with PLA, which printed easily but couldn’t handle heat or moisture. ABS was more durable but prone to warping. After testing several materials, we found that PETG offered the best balance of strength, flexibility, and chemical resistance—perfect for bathrooms. It resists bleach, humidity, and wear without becoming brittle over time.

Our first adapters were printed in basic gray PETG, but customers quickly started asking for other colors. That led us to experiment with new filaments, and today we offer multiple color-matched options including white, biscuit, almond, and light gray. While the matches are close, we note that they aren’t perfect—vintage glazes vary over time. For customers seeking a more exact look, our adapters can also be lightly sanded and painted using plastic-bonding spray paints.

Each adapter is printed in small batches, inspected by hand, and shipped with corrosion-resistant stainless hardware and flat-bottom leveling bumpers. These ensure the seat rests evenly and securely on the bowl—no rocking, no guesswork.

While specifically designed for Case 1000 and 1100 toilets, the adapter might also fit certain Briggs 7420, Kohler Rochelle, or Universal Rundle models that share a similar tank-front bolt pattern. However, compatibility with those models has not been confirmed in every case.

Retrofit Seats LLC is not affiliated with Case, Briggs, Kohler, or Bemis—we’re just the family that finally cracked the code for a proper retrofit, and we’re proud to help others hold onto the fixtures that still work like they were built yesterday.