A genuine Thetford OEM lip seal designed to fit the waste-holding tank blade assembly on Thetford cassette toilets manufactured after July 2000. This essential part ensures a watertight seal between the toilet bowl and the waste tank, preventing leaks, odours, and sticking blades.

If your toilet smells, leaks, or the blade is difficult to open, replacing the lip seal will usually restore smooth, leak-free operation.

Part Number: T23721

Material: Flexible, chemical-resistant rubber

Function: Waste blade lip seal

Diameter: Approx. 120 mm

Kit Includes: 1 × Lip seal (rubber blade seal)

Compatability:

Fits Thetford cassette toilets manufactured after July 2000

• C2, C3, C4 (post-07/00 models)

• C200, C220, C250, and C260 series

Frequently Asked Questions 

Q: What does this seal do?
It seals the gap between the toilet bowl and the waste tank, preventing leaks and odours, and allowing the sliding blade to operate smoothly.

Q: How do I know if I need a new lip seal?
You should replace it if you notice:

• Water leaking from the bowl into the tank

• The blade is difficult to open or close

• Persistent odours from the toilet

• The seal is visibly cracked, flattened, or sticky

Q: How often should I replace the lip seal?
Thetford recommends replacing it every 2–3 years, or sooner if your RV is used frequently or stored in extreme temperatures.

Q: Can I use silicone spray or petroleum jelly on it?
No , these products can damage the rubber. Use only Thetford Seal Lubricant, which is safe and extends the life of the seal.