If your toilet refills after you flush but takes a long time to do so, it can be frustrating and inconvenient. A slow-filling toilet is usually caused by restricted water flow or a partially blocked fill valve, not a problem with the drain.
In most cases, the issue is mechanical and fixable without replacing the toilet.
Quick Answer:
A toilet fills slowly when water flow to the tank is restricted. This is most often caused by a partially closed supply valve, debris inside the fill valve, a clogged inlet screen, or low water pressure feeding the toilet.
Why This Happens
Toilet tanks are designed to refill quickly so the toilet is ready for the next use. When something limits water entering the tank, refilling slows down noticeably.
Common causes include:
- A toilet supply valve that isn’t fully open
- Sediment or mineral buildup inside the fill valve
- A clogged inlet screen in the fill valve
- A kinked or aging supply line
- Gradually declining fill valve performance
Unlike a toilet that won’t refill at all, slow filling usually means water is getting through — just not enough of it.
Step-by-Step: How to Fix a Toilet That Fills Slowly
Step 1: Check the Supply Valve
Locate the shutoff valve behind or below the toilet.
- Turn it fully counterclockwise
- Do not assume it’s fully open based on position alone
A partially closed valve is the most common cause of slow refilling.
Step 2: Inspect the Supply Line
Look at the flexible hose running from the valve to the tank.
Make sure it:
- Isn’t kinked or bent sharply
- Isn’t pinched behind the toilet
- Isn’t leaking or corroded
Even a small restriction can slow the refill noticeably.
Step 3: Clean the Fill Valve Inlet
Sediment often builds up where water enters the fill valve.
To clean it:
- Turn off the supply valve
- Flush the toilet to empty the tank
- Remove the fill valve cap (design varies)
- Rinse debris from the inlet and internal screen
This step alone resolves many slow-fill issues.
Step 4: Watch the Refill Cycle
Turn the water back on and flush the toilet.
Observe:
- How fast water enters the tank
- Whether flow is steady or weak
- Whether the valve shuts off cleanly
If refilling improves but is still inconsistent, the issue may overlap with a toilet that keeps running intermittently.
Step 5: Consider Fill Valve Wear
If the toilet is older and cleaning doesn’t help, the fill valve may simply be worn.
Fill valves are inexpensive and designed to be replaced when performance declines.
What Not to Do
- Don’t ignore slow refilling for long periods
- Don’t keep flushing repeatedly to “force” refilling
- Don’t overtighten supply connections
- Don’t pour cleaning chemicals into the tank
Slow refilling often worsens over time if not addressed.
When to Call a Professional
Call a plumber if:
- Refilling remains extremely slow after cleaning
- Water pressure is low throughout the house
- Multiple toilets refill slowly
- The supply valve or line is leaking
These signs can indicate a broader supply or pressure issue.
Safety Notes
- Turn off the toilet supply before disassembly
- Keep towels nearby when working inside the tank
- Avoid stressing plastic valve components
- Replace cracked or brittle parts promptly
Common Homeowner Questions
Is a slow-filling toilet wasting water?
Not directly, but it can encourage repeated flushing, which increases water use.
Can low house water pressure cause this?
Yes, but most slow-fill problems are localized to the toilet itself.
Should I replace the fill valve or clean it first?
Cleaning is worth trying first. Replacement is usually the next step if performance doesn’t improve.