Why Is My Toilet Slow to Fill?

Have you noticed that your toilet is taking longer to refill after flushing? This is a common toilet problem with multiple possible causes. Fortunately, none of them are major concerns or costly to deal with. Follow this guide to get your slow toilet functioning efficiently again. 

How to Fix a Slow-Filling Toilet 

Finding out why your toilet is slow to refill is your first step toward fixing it. Keep in mind these potential reasons and how to handle each one. 

Partially Closed Water Supply Valve 

Check behind the toilet for the water supply hose connected to the wall. You’ll see a valve connecting to it, which enables you to turn off the water when your toilet is being repaired or replaced. Make sure this value is open by turning it to the left. 

Problems with the Fill Valve or Tube 

The fill valve, which is close to the top of a vertical tube-shaped part in the toilet tank, manages the water flow into the tank. A toilet fill valve might degrade, clog or slip out of alignment after years of use, stopping the tank from filling appropriately. Follow these tips to adjust, unclog or fix the fill valve: 

  • Search for the fill valve: Open the toilet tank lid and find the fill valve inside. It’s usually installed on the left side with a tailpiece extending through the bottom of the tank and linking to the supply tube and shut-off valve. 
  • Adjust the fill valve: Be certain the fill valve is secure and evenly fastened to the tube. Adjust the fill valve height if necessary by twisting the adjustment knob (typical to newer toilets) or find a flathead screwdriver and loosen the adjustment screw (required for older toilets). Then, check that the water level is approximately one inch below the top of the overflow tube. 
  • Clean the fill valve: To get rid of mineral buildup and other dirt from the valve, first shut off the water in the rear of the toilet and take off the fill cap. Then, slowly turn the water back on, cupping your hand over the valve to prevent from being sprayed by the water. Let the water flow for a few seconds to flush out dirt. Next, scrub away mineral buildup on the fill cap. If you observe cracks or substantial wear and tear, replace the valve. 
  • Clean the valve tube: Debris inside the valve tube could also be the culprit. Turn off the water supply and take off the valve hardware. Then, run a thin wire or bottle brush down the tube. Start the water supply slightly to rinse away the remaining residue. Replace the valve hardware and see if the toilet fills faster now. 

Waterlogged Float Ball 

The float ball in older toilet models rises with the water level, closing the fill valve when the tank is full. If the float ball is filled with water, it blocks the tank from filling properly. 

Remove the tank lid and look inside. A partially submerged float ball may be waterlogged. Before running out to buy a new ball, look at the float arm it’s connected to. If the arm is pointed too low in the tank, bend it up slightly to elevate the ball’s height. 

If this doesn’t work, then it might be time to just replace the component entirely. But it’s worth remembering that this is old toilet technology, so it might possibly be better to update the existing tank hardware or change out the toilet completely. 

Plugged Plumbing Vent 

Your home plumbing system includes vents that enable air to enter the pipes. If they become clogged, tension may build within the pipes, stopping the water from flowing. This can, in turn, make your toilet slow to fill or even cause the bowl to flood. 

You need to get on the roof to search for clogged plumbing vents. Search for long, vertical PVC pipes poking up from the roof tiles. Clear away any animal nests, deep snow or other obstructions you find to ensure your plumbing works properly. 

Leaky or Blocked Pipe 

If there’s nothing apparently wrong with the water supply valve, fill valve and tube, float ball or plumbing vents, the slow toilet issue could stem from your supply pipes. A water line leak could stop your toilet tank from filling appropriately. It’s best to hire a licensed plumber to handle these issues. 

Schedule Toilet Repair with Service Experts Heating, Air Conditioning & Plumbing 

Is your toilet still not working right? Turn to Service Experts Heating, Air Conditioning & Plumbing for dependable toilet repair in the U.S.. We can pinpoint the reason why this is happening and perform a cost-effective repair. If the fixture has reached the end of its average life span, our specialists can suggest high-efficiency toilet replacement in the U.S.. We’ll help you pick out the replacement model and install it on your behalf. Rest assured that every job we execute is backed by a 100% satisfaction guarantee! To schedule a visit from us, please call Service Experts Heating, Air Conditioning & Plumbing today. 

Savings For You

See All Offers Here >


  • Save $50 on a Paid Service
  • Written 100% Satisfaction Guarantee
  • Plus, ask how to save an additional 15% and waive your trip charge!


  • Prevent costly damage from water leaks, drain clogs and tank damage
  • Written 100% Expert Service Guarantee

© 2024 Service Experts, Service Experts Heating & Air Conditioning, and the Service Experts logo and design are registered trademarks of Service Experts LLC and used under license by SE Canada Inc. All Rights Reserved. *Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.

Chat with a Service Experts Professional