Why Is My Toilet Slow to Fill?

You flushed and now you have to wait; sound familiar? This is a frequent toilet issue with multiple possible causes. Fortunately, none of them are major concerns or expensive to fix. Follow this guide to get your slow toilet flowing quickly again. 

How to Repair a Slow-Filling Toilet 

Finding out why your toilet is slow to fill is your first step toward fixing it. Consider these possible reasons and how to deal with each one. 

Partially Closed Water Supply Valve 

Look behind the toilet for the water supply hose connected to the wall. You’ll find a valve connecting to it, which helps you to turn off the water during toilet repairs and replacements. Check this valve to make sure it’s completely open. 

Issues with the Fill Valve or Tube 

The fill valve, which can be found close to the top of a vertical tube device in the toilet tank, regulates 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, clear out or fix the fill valve: 

  • Locate the fill valve: Remove the toilet tank lid and find the fill valve inside. It’s usually secured on the left side with a tailpiece extending through the bottom of the tank and attaching to the supply tube and shut-off valve. 
  • Adjust the fill valve: Make sure the fill valve is secure and evenly attached to the tube. Adjust the fill valve height if necessary by twisting the adjustment knob (common to newer toilets) or loosening the adjustment screw with a flathead screwdriver (required for older toilets). After that, verify that the water level is roughly one inch below the top of the overflow tube. 
  • Clear debris from the fill valve: To get rid of mineral buildup and other debris from the valve, first shut off the water in the back of the toilet and remove the fill cap. After that, slowly turn the water back on, cupping your hand over the valve to prevent from being sprayed by the water. Allow the water to flow for a few seconds to flush out the buildup. Next, scrub away mineral buildup off the fill cap. If you notice cracks or significant wear and tear, replace the valve. 
  • Clean the valve tube: Debris trapped in the valve tube could also be the culprit. Shut off the water supply and take off the valve hardware. Next, run a slim wire or bottle brush into the tube. Open the water supply slightly to rinse away the leftover residue. Replace the valve hardware and verify if the toilet fills faster now. 

Waterlogged Float Ball 

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

Take off the tank lid and peek inside. A partially sunken float ball may be waterlogged. Before you replace the ball, look at the float arm it’s connected to. If the arm is pointed too low in the tank, bend it up somewhat to elevate the ball’s height. 

If that does not do the trick, then it might be time to just replace the component entirely. Just remember that this is an older toilet design, so it may be better to modernize the existing tank components or change out the toilet completely. 

Plugged Plumbing Vent 

Your home plumbing system uses vents that enable air to enter the pipes. If they become clogged, stress may build throughout the pipes, blocking the water from flowing. This can, in turn, make your toilet slow to fill or even cause the bowl to overrun. 

You need to get on the roof to search for clogged plumbing vents. Start looking for long, vertical PVC pipes poking up from the tiles. Get rid of any animal nests, deep snow or other obstructions you notice to help your plumbing work as intended. 

Leaky or Blocked Pipe 

If you can’t find anything wrong with the water supply valve, fill valve and tube, float ball or plumbing vents, the slow toilet problem could stem from your supply pipes. A leak or blockage in the water line could stop your toilet tank from filling properly. It’s a good idea to hire a licensed plumber to fix these issues. 

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

If these tips did not handle your issue, look to Service Experts Heating, Air Conditioning & Plumbing for quality toilet repair in the U.S.. We can identify the reason why this is happening and perform the most appropriate repair. If the fixture has come to the end of its average life span, our team can propose high-efficiency toilet replacement in the U.S.. We’ll help you decide on the replacement model and install it for you. You can relax knowing that every job we complete is backed by a 100% satisfaction guarantee! To schedule a visit from us, please connect with 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.