Thetford has been making toilets for the recreational vehicle (RV) manufacturing industry since the 1970s. They manufacture everything from the humble Porta-Potti to porcelain units styled just like an upscale household unit, along with a comprehensive range of toilet care and cleaning products. User manuals for the majority of their products are available for download free of charge at their website. The user-serviceable parts of a Thetford toilet are its seat and seat cover, the blade seal, the water valve and the vacuum breaker. Repairing a malfunctioned unit is a straightforward project.
Release the seat and seat cover by sharply pushing backward on the hinges when the seat and cover are open. Fitting a new assembly is by reversing that process.
Check to make sure no debris is trapped in the groove into which the blade seats if the toilet bowl fails to hold water, and check that the blade seal is firm and plump. If the seal is decayed, stiff or powdery, it must be replaced. If the blade seats well into a well-conditioned seal the toilet may be slightly warped from being fastened to the floor too tightly. To free off the blade mechanism, use your socket set to slightly loosen the nuts on the closet bolts which hold it to the floor.
Flush the toilet and observe the behaviour of the water. If it continues to drip into the toilet bowl more than 15 seconds following a flush, the water valve has malfunctioned and must be replaced. If water leaks behind the toilet after flushing the vacuum breaker (an anti-siphon device mandated by code) has malfunctioned and must be replaced. Both are accessed by lifting the toilet completely away from the floor.
Remove the closet nut/bolt/washer assemblies if you need to lift the toilet away completely. Press the foot pedal and the front assembly will be visible behind it; remove the nut from the bolt. Lift the seat and remove it so the access hole cover is revealed, then use a half-inch deep well socket on a 12-inch extension bar to remove the nut from the rear assembly. Raise the toilet straight up to clear the lip of the black water tank, and release the water supply pipe by loosening the hose clamp securing it in place.
Thetford's Customer Service Department can be reached at 1-800-543-1219. When purchasing your replacement parts, be sure to have on hand a note listing the manufacturer, model, colour and year of manufacture (usually knowing the RV's year of manufacture is enough). If you are picking up the parts from an RV supplier, take the broken part with you for comparison.
Never use petroleum jelly to lubricate the blade seal. Use a proprietary silicone-based drain valve lubricant.