Why Is My Toilet Slow to Fill?

You flushed and now you have to wait; sound familiar? This is a frequent toilet problem with several possible reasons. Thankfully, none of them are major concerns or costly to deal with. Follow this guide to get your slow toilet functioning efficiently again. 

How to Address a Slow-Filling Toilet 

Understanding why your toilet is slow to fill is the first step toward fixing it. Keep in mind these possible reasons and the best way to handle each one. 

Partially Closed Water Supply Valve 

Check behind the toilet for the water supply line connected to the wall. You’ll find a valve connected to it, which allows you to close off the water during toilet repairs and replacements. Make sure this value is open by turning it to the left. 

Issues with the Fill Valve or Tube 

The fill valve, which you’ll find attached to the top of a vertical tube-shaped part in the toilet tank, controls the water level flowing into the tank. A toilet fill valve could break down, clog or slip out of alignment after years of use, preventing the tank from filling right. Follow these tips to adjust, clean or fix the fill valve: 

  • Search for 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 linking to the supply tube and shut-off valve. 
  • Adjust the fill valve: Be sure that the fill valve is secure and evenly connected to the tube. Adjust the fill valve height if required by twisting the adjustment knob (common to newer toilets) or loosening the adjustment screw with a flathead screwdriver (required for older toilets). After that, make sure the water level is approximately one inch below the top of the overflow tube. 
  • Clean the fill valve: To take out mineral buildup and other sludge from the valve, first shut off the water in the rear of the toilet and take off the fill cap. After that, slowly turn the water back on, cupping your hand over the valve to avoid getting sprayed. Let some water flow for a few seconds to flush out debris. Next, scrub away mineral buildup off the fill cap. If you detect cracks or excessive wear and tear, replace the valve. 
  • Clean the valve tube: Debris inside the valve tube could also be at fault. Shut off the water supply and take off the valve hardware. Afterward, run a slim wire or bottle brush into the tube. Turn back on the water supply slightly to rinse away the excess residue. Replace the valve hardware and check if the toilet fills quicker. 

Waterlogged Float Ball 

The float ball in older toilet models rises with the water level, sealing the fill valve once the tank is full. If the float ball takes on water, it prevents the tank from filling properly. 

Take off the tank lid and peek inside. A partially sunken float ball could be waterlogged. Before you replace the ball, examine the float arm it’s secured to. If the arm is fixed too low in the tank, bend it up slightly to lift the ball’s height. 

If this doesn’t work, you might want to simply buy a new float ball; the average cost of this product ranges between $7-$20 in most hardware or home improvement stores. Just be aware that this is an older toilet design, so it might possibly be better to upgrade the existing tank parts or change out the toilet altogether. 

Blocked Plumbing Vent 

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

You’ll need to jump up on the roof to search for clogged plumbing vents. Look for long, vertical PVC pipes poking up from the roof tiles. Get rid of any animal nests, deep snow or other obstructions you find to guarantee that your plumbing can function as intended. 

Leaky or Blocked Pipe 

If nothing is wrong with the water supply valve, fill valve and tube, float ball or plumbing vents, the slow toilet dilemma could stem from your supply pipes. A water line leak could restrict your toilet tank from filling correctly. It’s best to hire a licensed plumber to fix 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 reliable toilet repair in the U.S.. We can pinpoint the reason why your toilet is slow to fill and perform a budget-friendly repair. If the fixture has come to the end of its typical life span, our specialists can recommend high-efficiency toilet replacement in the U.S.. We’ll help you decide on the replacement model and install it for you. Relax knowing that every job we perform is supported by a 100% satisfaction guarantee! To schedule a visit from us, please contact 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