Both my gray and black tank dump valves( Thetford 01447 ) were weeping between the halves (at the gasket) I found these 09872 rebuild kits Thetford 09872 Slide-Ez Valve Repair Package - All Plastic | Boatplicity (https://boatplicity.com/9069330-thetford-09872-rebuild-kit?utm_source=orderconfirmation&utm_medium=email&utm_campaign=OrderConfirmation) couple hours of work to pull them apart, clean and reassemble, there were a couple extra (not needed seals). They work great and no more leaks..