Gaskets at the discharge valve and fill cap are small, inexpensive parts, and a worn one is a common cause of slow weeping. Reconditioners commonly replace them as part of the process. Which material goes back in matters more than the cost suggests.
The common types
- EPDM (ethylene propylene diene). General-purpose and inexpensive. Handles most water-based chemistry. Poor with petroleum oils and many solvents.
- Food-contact EPDM. The same base material in a grade documented for food contact.
- FKM (often sold as Viton). Handles many solvents, acids and fuels. Costs more than EPDM.
- PTFE-encapsulated. Very chemically inert. Used when other materials will not hold up.
How gaskets fail
- Compression set: the gasket slowly loses its spring and stops sealing. Common in normal service.
- Swelling and softening: the wrong elastomer absorbs the product. Typical of EPDM in solvent or oil service.
- Hardening and cracking: often from heat or age.
Temperature matters too
Repeated heating and cooling works a gasket harder than steady temperature. If your product is filled hot or the tote sits in big temperature swings, expect gaskets to need replacement sooner.
What to ask
Tell the partner supplier what you will store and at what temperature, and ask which gasket material is fitted. If in doubt, check the product’s safety data sheet and a chemical compatibility chart.