The four leak types and what each costs to fix
Toilet leaks come from four locations. Pros diagnose by where the water appears and when.
Type 1: Internal flapper / flush-valve leak
Symptom: water trickles into the bowl between flushes, you hear "phantom" refilling every 10-30 minutes when no one used the toilet. Wastes 50-200 gallons per day on a continuous leak.
Cost to fix: $85-$160. New flapper $5, fill valve $12, flush valve $25. Labor 30-45 minutes.
Type 2: Fill valve overflow
Symptom: tank water level rises above the overflow tube, constant trickling sound, water bill jumps.
Cost to fix: $80-$150. Replace fill valve and adjust water level. Labor 30 minutes.
Type 3: Tank-to-bowl gasket leak (two-piece toilets only)
Symptom: water drips from where the tank meets the bowl, runs down the back of the bowl onto the floor. Usually only during/after flushing.
Cost to fix: $120-$220. Remove tank, replace spud gasket and tank bolts. Labor 45-60 minutes.
Type 4: Base/wax ring leak
Symptom: water appears at the toilet base after each flush. Sewer-gas smell. Toilet may rock slightly.
Cost to fix: $120-$280. See our dedicated wax-ring-replacement service page.
How pros diagnose
Step 1: Food coloring test. Drop colored dye into the tank. Wait 20 minutes without flushing. If color appears in the bowl, you have a flush-valve / flapper leak. If not, the leak is external.
Step 2: Dry-paper test at base and tank-to-bowl joint. Place dry paper towels around the base and at the tank-bowl junction. Flush and watch for moisture appearance. Tells you whether the leak is at the wax ring or the spud gasket.
Step 3: Listen test. A continuously running fill valve has a characteristic high-pitched whine. Phantom refills (every 10-30 minutes) point to flapper leak.
What you save by fixing fast
A continuous toilet leak wastes 100-200 gallons per day. At average $11 per 1,000 gallons of combined water+sewer, that\'s $35-65 per month, $400-780 per year added to your bill. The $150 repair pays for itself in 2-4 months.
Some utilities also offer "leak adjustments" — a one-time bill credit if you can document repair of a sudden leak. Check your utility\'s policies and save the repair invoice.
When to choose full toilet replacement
If your toilet is 15+ years old and has multiple leak points (e.g., flapper + tank-bolt + maybe wax ring), a full toilet replacement at $400-700 installed is more cost-effective than chasing individual leaks. New WaterSense toilet also saves $30-100 per year in water usage going forward.