Quick Answer:
If the toilet still runs after replacing the fill valve, most likely the refill tube is routed wrong, the fill valve height is incorrect, or the float level needs adjusting. Confirm the refill tube is clipped to the overflow tube (not shoved down it), set the float to the manufacturer’s mark, and retest the tank fill.
Why This Happens
New fill valves come in many shapes. If the valve sits too low or the refill tube is pushed into the overflow, water can siphon continuously into the bowl and make the toilet run. If the float isn’t set to the correct mark the tank will overfill and the valve never shuts off. Minor leaks at the flapper or a bad seal can also trigger continuous refilling.
Two common patterns you might notice: Toilet runs intermittently every few minutes when the tank slowly leaks down, or sometimes the problem appears only at night and sounds different — such as when the house is quiet — similar to Toilet runs only when house is quiet.
Step-by-Step What to Do
1. Shut off water and drain the tank
- Turn the shutoff valve at the wall clockwise to stop water to the toilet.
- Flush to drain most of the water from the tank. Use a sponge or towel to remove remaining water if needed.
2. Check how the refill tube is routed
- Find the small plastic refill tube that runs from the fill valve to the overflow tube.
- Confirm the tube is clipped to the outside of the overflow tube and its end sits above the overflow lip. The refill tube must not be shoved down the overflow; set float level to manufacturer mark and retest.
- If the refill tube is inside the overflow, pull it out and reattach the clip so it points into the overflow but not inserted down the tube.
3. Confirm the fill valve height
- Look for the manufacturer’s height mark or adjustment collar on the fill valve. The valve top should be at the recommended height above the overflow tube so it refills properly.
- Adjust the valve according to the maker’s instructions—most modern valves have a twist or slide adjustment.
4. Set the float level
- Locate the float (cup or rod style) and set it to the manufacturer’s water level mark. This mark is usually stamped on the valve body or shown in the instructions.
- Water level should be about 1 inch below the top of the overflow tube or at the exact mark described by the manufacturer. After adjusting, turn the water back on slowly and let the tank fill.
5. Test and observe
- With the tank filled, watch for a minute to see if water continues to flow into the overflow or if the valve shuts off and stays closed.
- Flush once or twice and recheck the refill tube position and final water level. If it still runs, check the flapper for a bad seal or debris before changing parts again.
What Not to Do
- Don’t route the refill tube down into the overflow—this can cause constant running.
- Don’t overtighten plastic fittings; you can crack the tank or strip threads. Tighten snugly by hand and finish with a small wrench only if needed.
- Don’t ignore a persistent leak. If you’re unsure, a plumber is appropriate to avoid wasting water or causing tank damage.
When to Call a Professional
Call a plumber if you’ve confirmed the refill tube and float are set correctly but the toilet still runs, if you suspect a cracked tank or corroded valve parts, or if you’re uncomfortable making the adjustments. A pro can quickly identify worn parts (flapper, seat, or valve) and replace them correctly.
Safety Notes
- Always turn off the water supply before disassembling the fill valve or working inside the tank.
- Work gently around porcelain. Use towels to protect the tank and avoid dropping tools that could crack it.
- If replacement parts don’t fit easily, stop and verify model compatibility rather than forcing components together.
Common Homeowner Questions
- Why does the toilet keep running after a fill valve replacement? — Usually the refill tube is misrouted, the float level is wrong, or the valve height is incorrect.
- How high should the fill valve be set? — Set it to the manufacturer’s height or so the water fills about 1 inch below the overflow tube.
- Can I fix it myself or do I need to call someone? — Try the checks above first; call a plumber if adjustments don’t stop the running or if you’re unsure.
For more related articles, see the nan hub.