Quick Answer:
If the refill time keeps getting longer over weeks, it usually means something is slowly restricting water flow. Progressive buildup — mineral scale, rust, or debris — on the inlet screen, in the supply line, or inside the fill valve is the most common cause. A few checks and a gentle cleaning often restore normal speed; if not, call a plumber.
Why This Happens
- Mineral deposits (scale) form slowly where water moves through small openings. Over time those deposits narrow passages and reduce flow.
- Rust or sediment from old pipes can accumulate in the shutoff valve, flex line, or fill-valve inlet screen and block water movement.
- Worn or partially blocked fill valves lose efficiency gradually, so refill time gets worse week by week rather than failing all at once.
- Any progressive restriction in the supply path — from the house shutoff to the fill mechanism — produces the symptom you describe.
Step-by-Step What to Do
1. Confirm the pattern and isolate the fixture
- Note how refill time changes after a fresh flush and over several days. If the slowdown is consistent and gradual, that points to buildup rather than a sudden failure.
- Check other fixtures fed by the same supply. If multiple fixtures show reduced flow, the issue may be upstream (main valve or supply line). If only one toilet is affected, focus on that tank.
2. Turn off the water and inspect visible parts
- Shut the toilet shutoff valve clockwise to stop supply before working on the tank.
- Remove the tank lid and look at the fill valve inlet and the fill valve itself. Many valves have a small removable inlet screen or filter where the supply connects; inspect it for grit, rust, or white scale.
- Also check the external flex supply line at both ends for kinks, corrosion, or debris.
3. Clean or replace the inlet screen and supply line
- Carefully remove the inlet screen (if present) and rinse it. Gently soak in white vinegar for 30–60 minutes to loosen mineral scale, then rinse and reinstall.
- If you see heavy deposits inside the flex line or the valve, replace the flex supply line and consider a new fill valve. Replacement flex lines are inexpensive and straightforward to swap.
- After cleaning or replacing parts, turn the shutoff back on slowly and test refill time. Watch for leaks.
4. Check and test the fill valve
- Some fill valves allow you to flush out debris by briefly turning the shutoff off and on or by lifting the valve mechanism per the manufacturer’s instructions. Follow those steps if they apply to your valve.
- If the valve still fills slowly after cleaning screens and the supply line, the valve itself may be worn. Replacing the fill valve is a common, low-cost fix.
5. Follow-up monitoring
- Monitor refill times for a few weeks after cleaning or replacement. Gradual reappearance of the slowdown suggests an upstream source or hard water issues causing rapid redeposit.
- If hard water is present, consider more frequent checks or installing an appropriate water-treatment option to reduce recurring buildup.
For related reading about similar symptoms, see Toilet refills slowly and Tank takes forever to fill.
What Not to Do
- Don’t ignore gradual slowdown — it often indicates buildup; if cleaning doesn’t help, a plumber is appropriate.
- Don’t force or rapidly wrench fittings; that can damage valves or fittings and cause leaks.
- Avoid pouring strong acids or undiluted harsh chemicals into the tank to remove scale — they can damage rubber parts and finishes and create hazardous fumes.
- Don’t assume a quick fix will last if you have very hard water; repeated clogs mean you should address the water quality or replace parts with hard-water-friendly components.
When to Call a Professional
- If cleaning inlet screens and replacing the flex line or fill valve doesn’t restore normal refill time.
- If multiple fixtures supplied by the same line show progressive slowdown — that can signal an issue in the house supply or corrosion in older plumbing.
- If you find signs of pipe corrosion, persistent leaks, or if shutoff valves are seized — a plumber can diagnose and safely repair or replace those components.
Safety Notes
- Turn off water at the shutoff before working on the tank to avoid flooding.
- Wear gloves and eye protection when cleaning parts or handling vinegar/cleaners.
- Use basic hand tools and take care not to overtighten plastic fittings. If a valve seems stuck, call a plumber rather than forcing it.
Common Homeowner Questions
- How long should a tank refill take? About 1–2 minutes for a normal toilet tank; significantly longer is a sign of restricted flow.
- Can I clean the inlet screen myself? Yes — remove, soak in vinegar, rinse, and reinstall; replace if damaged.
- Will replacing the fill valve fix a gradual slowdown? Often yes, especially if the valve is worn or clogged; but check supply lines and screens first.