RO leaking from a filter housing: the O-ring, not the housing

The most common RO leak is also the most fixable. It shows up right after a filter change, at the seam where the housing screws on, and it is almost never the housing itself.

The O-ring

Inside the housing lip is a rubber ring that makes the seal. It gets pinched, twisted or dislodged when the housing is screwed back on, especially if it was dry. It also hardens with age and stops sealing.

The fix

• Switch the RO off and close the inlet valve
• Unscrew the housing and remove the O-ring
• Check it for cuts, flat spots or a twist
• If it looks fine, apply a thin smear of food-grade silicone grease and reseat it flat in its groove
• If it is damaged, replace it — they are cheap and standard
• Screw the housing back on hand-tight, then a quarter turn more. Not with a wrench.

If it still leaks

The housing may be cross-threaded — back it off and start again squarely. Or the housing has a hairline crack from over-tightening in the past, and needs replacing.

Leaks elsewhere

From a push-fit tube: the tube is not pushed fully home, or its end is scored. Cut a clean end and reinsert. From the membrane housing cap: same O-ring logic. From the tank valve: the valve washer.

Over-tightening is the cause of more housing cracks than anything else. The O-ring does the sealing, not the force. If you need a tool to stop a leak, something else is wrong.

When to call

A leak you cannot find, a crack in a housing, or a leak that comes back after a new O-ring. All quick, and a service visit includes checking every seal.