Why Is My Water Filter Leaking from the Bottom or Top?

Water filters leak from the top or bottom when seals fail, parts crack, or excess pressure builds in the housing. The most common cause is a flattened or mis-seated O-ring after a filter change that no longer seals the cap or canister. A cracked sump or head usually means replacement, not more tightening, and pressure spikes can force water past good seals. Our licensed plumbers follow local plumbing codes and service filtration, RO, and softener systems throughout the Indianapolis area. A dry O-ring can seal at first but seep later as temperatures change; a thin coat of silicone-safe lubricant often prevents that.

Try these checks in order:

• Reseat or replace the O-ring; clean the groove and lightly lubricate.
• Hand-tighten the canister; avoid cross-threading and over-torque.
• Inspect for hairline cracks in the sump or head and replace if found.
• Verify the cartridge is the correct size and fully seated.

Shut off the filter’s water supply and relieve pressure before opening the housing.

Updated: 2026-07-04

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