shower arm leaking when not in use
If you replaced the cartridge a set it exactly the same way, you may have set it to the wrong &quot;off&quot; position by duplication of the &quot;leaking&quot; one. The temperature limiter also sets the stop point on many diverter.
See &quot;stop tube kit&quot;

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Test
To test if this is the issue, remove the hardware and very slowly turn the cartridge and try to find off dead center.
If this fails
If this doesn't solve the problem then it's likely that the diverter body has worn or has developed sediment. It may need to be thoroughly cleaned or replaced.