Start with the application.
EPDM is a common candidate for water service and outdoor environments. Curing system, fluid additives and operating conditions determine the final suitability.
What to verify
Generally unsuitable for petroleum oils and fuels. Do not substitute EPDM into a mineral-oil circuit based on size alone. Potable-water service requires appropriate evidence.
Specify more than the polymer
Record dimensions, compound identification, hardness, tolerances, working conditions and quantity. Ask for a grade-specific datasheet before design approval.
General polymer guidance is not a guaranteed rating for a finished O-ring. Validate performance in the intended assembly.
Dimensions and standards
Give the inside diameter and cross-section with units. If using a standard size, include its exact designation and applicable revision. Confirm dimensional tolerances against your drawing.
Technical references
General background: Parker O-Ring Handbook and Trelleborg elastomeric O-rings. These references do not certify Rubrings products or establish any affiliation.