The Korky 528 is one of the most popular toilet fill valves out there—quiet, adjustable, and anti-siphon certified. But like any plumbing part, it can act up. Whether your toilet’s not refilling, making strange noises, or leaking from the top, this guide will walk you through the most common issues with the Korky 528 and how to fix them.
Quick refresher: what is the Korky 528?
The 528 is an adjustable fill valve that replaces old or broken float-style valves. It controls how your toilet tank refills after each flush and includes anti-siphon protection (so dirty water doesn’t backflow into your water supply).
Common problems and how to fix them
1. Toilet not filling after flush
This is often caused by debris inside the valve or a stuck float. Here’s what to do:
Try this:
- Turn off the water at the shutoff valve
- Remove the top cap of the fill valve (twist counterclockwise while pressing down)
- Hold a cup or towel over the opening
- Turn water on briefly to flush out debris (2–3 seconds is enough)
- Reinstall the cap and turn the water back on
If that doesn’t help, the valve may need to be replaced—especially if it’s several years old.
2. Water keeps running or doesn’t shut off
This usually means the float is stuck or misadjusted, or the flapper isn’t sealing.
Steps to try:
- Check that the float moves freely up and down
- Make sure the refill tube isn’t inserted too far into the overflow pipe—it should clip just above it
- Adjust the float height using the twist collar to raise or lower water level
- Check the toilet flapper—if it’s warped or leaking, water will constantly escape into the bowl
Tip: The water level should sit about 1 inch below the top of the overflow pipe.
3. Whistling or squealing sound
That high-pitched noise is almost always due to debris or a worn diaphragm inside the valve.
Try flushing out the valve:
- Follow the same steps as in problem #1 to flush debris from the top of the fill valve
- If the noise continues, consider replacing the top cap assembly (you can get a replacement without buying the full valve)
Replacement part: Korky part #528GK (Genuine Replacement Cap and Seal Kit)
4. Water leaking from top of the valve
If you see water spraying or dripping from the top, the valve is either clogged internally or the cap seal is damaged.
Fix:
- Turn off water and remove the cap
- Inspect the rubber seal inside—if it’s torn, flattened, or cracked, replace it
- Flush the valve to clear blockages, then reinstall
If the seal looks fine but the leak continues, the internal parts might be worn—time for a full valve replacement.
5. Slow tank refill
This can be caused by low water pressure, debris in the shutoff valve, or a partially blocked fill valve.
Try this:
- Make sure the shutoff valve is fully open
- Disconnect the supply line and clean the inlet screen if it’s clogged
- Flush the fill valve to clear any debris (see step #1)
If you still get a trickle, the diaphragm inside the valve might be worn—replace the cap or full valve.
When to replace the whole valve
If flushing debris or adjusting the float doesn’t help—or if your valve is over 5 years old—it might be time for a full replacement. The Korky 528 is affordable and installs in under 10 minutes with just a pair of pliers.
Helpful tools
- Adjustable pliers or channel locks
- Towel or sponge (to soak up water in the tank)
- Bucket (for draining the supply line)
Final thoughts
The Korky 528 is one of the most reliable fill valves out there—but like any valve, it can get clogged or wear out over time. If your toilet’s acting up, try flushing the valve and checking the float before jumping to replace it. Most issues are a quick fix with no plumber needed.
Need replacement parts? Visit Korky’s official site or find genuine 528 repair kits at most hardware stores.