No, you should not use WD-40 on a shower diverter valve because its petroleum base breaks down and degrades rubber O-rings and plastic seals over time, leading to premature leaks and mechanical failure. For safe, long-lasting maintenance, you should always clean mineral scale with white vinegar and lubricate moving parts using food-grade silicone grease (plumber's grease). Verification: Test the diverter action to ensure it slides smoothly without damaging internal rubber seals.
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