Quick Answer
Most shower filter leaks come from the threaded joints and are fixed by re-taping with Teflon tape and reseating the connection. Check the cartridge O-ring/seal if the housing itself leaks. Tighten by hand; avoid over-tightening.
Problem
A dripping or leaking shower filter is annoying and wastes water, but the cause is usually a simple seal issue rather than a broken part.
Product Recommendation
ZOOSHEN filters include sealing rings with the housing and cartridge. If a seal is damaged, replacement rings and cartridges are available.