Seam tape can fail by starting to peel away (often caused by washing), or can become flaky and powdery (usually caused by age).

Seam sealing stops water from leaking through the tiny holes creating by stitching on waterproofs. The tape is activated with heat and sticks over the stitching to create a waterproof seal. Over time this seam sealing tape can peel away, making the garment less waterproof.