Under-Sink Water Filter Problems: Common Issues and How to Fix Them

Most under-sink water filter problems have straightforward causes and fixes. Here’s a practical troubleshooting guide.

See our full Under Sink Water Filters Guide or call us on 1800 789 781 if you need help.

Problem 1: Reduced Water Flow

Most likely cause: Clogged cartridge. Replace the cartridge — this is the most common cause of flow reduction and the fix is straightforward. Browse our replacement cartridge range.

Other causes: Partially closed inlet shut-off valve (check it’s fully open), kinked water line, or a clogged sediment pre-filter if your system has one.

Problem 2: Dripping or Leaking Under the Sink

Most likely cause: Loose connection or a damaged O-ring on the filter housing. Turn off the inlet shut-off valve, dry the area, and identify the source. Tighten the connection or replace the O-ring. Apply a small amount of food-grade silicone grease to the O-ring before reassembling.

If the leak is from a water line fitting: Turn off the water supply and call a licensed plumber. Do not attempt to repair pressurised water line fittings yourself.

Problem 3: Unusual Taste or Odour

Most likely cause: Exhausted carbon cartridge. Replace immediately — a carbon cartridge past its service life provides no chlorine removal and can harbour bacteria. Browse our replacement cartridge range.

New system taste: A slight carbon taste from a new cartridge is normal. Flush for 5–10 minutes before use.

Problem 4: Noisy Operation

Most likely cause: Air in the water lines after a cartridge change. Run the filtered water tap for a few minutes to purge the air. This is normal after any cartridge replacement.

RO systems: A low hum from the RO membrane is normal during filtration. Loud rattling or banging is not — call us on 1800 789 781.

Problem 5: Water Bypassing the Filter

Most likely cause: Damaged or missing O-ring allowing water to bypass the cartridge. Replace the O-ring and ensure the cartridge is correctly seated. If the housing is cracked, replace the housing.

Frequently Asked Questions