How Do You Fix a Running Toilet?
A running toilet wastes 3,000 to 5,000 gallons of water per month more if the running is continuous. Most running toilet fixes are DIY-feasible with $5 to $20 in parts from any hardware store.
Diagnose With the Food Coloring Test
Put 5 to 10 drops of food coloring in the toilet tank. Do not flush. Wait 15 minutes. If color appears in the bowl: the flapper is leaking (water passing from tank to bowl continuously). This is the most common running toilet cause. The fix: replace the flapper a $5 to $15 part that fits over the drain hole at the bottom of the tank, available at any hardware store. Turn off the water at the supply shutoff under the toilet, flush to empty the tank, unhook the old flapper, and hook on the new one. Turn the water back on, let the tank fill, repeat the dye test to confirm the fix.
Fill Valve Failure
The fill valve refills the tank after flushing. A fill valve that is running continuously (the toilet sounds like it is constantly filling or hissing) is either: set with a float that is too high (water drains into the overflow tube continuously) or a worn fill valve that does not shut off correctly. Float adjustment: bend the float arm down slightly (for ball float types) or adjust the float position on the fill valve stem (for modern float types) to lower the water level below the overflow tube. If adjustment does not resolve it: fill valve replacement ($10 to $20 in parts) takes 15 to 30 minutes and requires turning off the supply and emptying the tank.
When to Call a Plumber
When the toilet bowl itself is cracking or leaking at the base. When the wax ring is failing (water seeping at the base of the toilet when flushed). When the flapper and fill valve replacement has not resolved the running and the cause is unclear. When the shut-off valve under the toilet will not close (a plumber replaces the shutoff valve and addresses the running toilet in the same visit). Most running toilet situations are DIY-resolvable; call a plumber for the base leak, wax ring, and shutoff valve scenarios.
Working With a Contractor on This Project
Getting the right outcome on any home services project starts before the work begins. A few consistent practices make the difference between a smooth project and a frustrating one.
Get at least two or three quotes. A single quote gives you no basis for comparison. Two or three quotes reveal the market rate for the work, expose scope differences between bidders, and let you assess contractor communication quality before any commitment is made. The lowest bid is not automatically the best value if the scope is thin or the materials are underspecified.
Ask for licenses and insurance before work starts. Verify current general liability insurance and, for any work involving workers on your property, workers compensation coverage. Licensing requirements vary by state and trade; confirm the specific requirements in your jurisdiction. A licensed contractor who carries appropriate insurance protects both parties if something goes wrong during the project. (For more on this, see Questions to Ask Before Booking Faucet Repair.)
Get the scope in writing. A written proposal that specifies materials, labor scope, timeline, what is included (permits, cleanup, disposal), and warranty terms is the foundation of a professional engagement. Verbal agreements on any of these points invite misunderstanding. For any project over $500, written scope is non-negotiable.
Clarify the payment schedule upfront. A reasonable payment schedule ties major payments to project milestones: a deposit at signing, a payment at material delivery or project start, and a final payment at completion after a walkthrough confirms satisfaction. A contractor who requires full payment upfront before work begins is a red flag in any trade.
Making a Confident Decision
The information in this article is designed to help you ask better questions of the professionals you work with, evaluate their answers with more confidence, and understand the decisions involved in this type of home services project. It is not a substitute for professional assessment of your specific home. (For more on this, see Questions to Ask a Plumber About Faucet Work.)
Every home is different. Roof slopes, local weather, tree exposure, soil conditions, and existing system condition all affect what the right solution is for your specific situation. The general principles here apply broadly, but a professional who assesses your home in person will give you guidance that accounts for the details that general articles cannot.
When you are ready to move forward, getting at least two or three quotes from licensed, insured, local contractors is the most important practical step. It lets you compare approaches, assess contractor quality, and confirm that the solution proposed matches your specific situation and budget.
Cost figures on this page were checked against published pricing on September 2, 2026. How we source cost data.
