Toilet Keeps Running? Fix It for Under $25 (and Stop the Waste)

Published by Clément Lacaille, Tech-Bharat · Updated September 28, 2026 · How we research

That faint hiss or periodic phantom refill from your toilet isn't just annoying — it's one of the most expensive small leaks in a California home. A running toilet can waste 200+ gallons per day, which shows up fast on a water bill and matters even more in a state where every district asks residents to conserve. The fix is usually a sub-$25 part and half an hour of your time.

Find the culprit in five minutes

Take the tank lid off and look. Three components cause nearly every running toilet:

• The flapper — the rubber disc at the bottom of the tank that lifts when you flush. If it's warped, mineral-crusted, or misaligned, water seeps continuously into the bowl.
• The fill valve — the tall assembly that refills the tank. A worn fill valve never fully shuts off, producing a constant hiss.
• The float — set too high, it lets water rise above the overflow tube, so the tank drains endlessly down the overflow and refills forever.

Quick test: put a few drops of food coloring in the tank and wait 15 minutes without flushing. Color in the bowl means the flapper is leaking. Water trickling into the overflow tube means the float is set too high or the fill valve won't close.

The fixes, cheapest first

1. Adjust the float (free). Turn the adjustment screw or slide the float clip so the water line sits about an inch below the top of the overflow tube.
2. Replace the flapper ($5–$10). Shut the supply valve, flush to empty the tank, unclip the old flapper, and match it at the hardware store — flappers aren't universal, so bring the old one.
3. Replace the fill valve ($10–$25). Modern universal fill valves install in 20–30 minutes with no special tools. Shut off the supply, drain the tank, unscrew the supply line and lock nut, swap the valve, and set the fill height.

Hard water accelerates all of this. In mineral-heavy areas around Fresno and Sacramento, flappers and valve seals can fail in two or three years instead of five or more, so keep a spare flapper on hand.

When a running toilet means something bigger

Call a professional if you notice any of these:

• You've replaced the flapper and fill valve and it still runs — the flush valve seat itself may be pitted, which can mean replacing the flush valve or the toilet.
• Water on the floor around the base, which points to a failed wax ring, a cracked tank, or a loose tank-to-bowl gasket rather than a running problem.
• The toilet runs and flushes weakly, which can indicate a partial clog or venting issue downstream.
• The shutoff valve under the toilet won't turn or leaks when you touch it — corroded angle stops are common in older homes and worth replacing while a pro is there.

Professional toilet repair in California typically runs $100–$300 for internal component replacement, more if the toilet has to be pulled. If your toilet is a pre-1994 model using 3.5+ gallons per flush, replacement deserves a look: many California water districts offer rebates on high-efficiency models, a topic we cover in our guide to drought-smart plumbing upgrades.

The conservation math

At 200+ gallons a day, a running toilet can leak more water in a month than a family uses for showers. Tiered water rates in much of the state mean that waste is billed at your most expensive rate. A $10 flapper often pays for itself before your next bill arrives.

Not confident pulling the tank apart, or suspect the problem goes beyond the usual parts? Describe the symptoms on Plumber Comparator and request your free quote — a licensed local plumber will get it sorted quickly.

Related topics

These topics used to have their own pages; their key facts and figures are gathered here.

Running Toilet? What It Costs to Fix

A toilet that hisses, gurgles, or refills itself every few minutes is one of the most common calls a California plumber gets, and one of the cheapest to fix — if it's caught early. Left alone, it's also one of the few plumbing problems that quietly drains money every single day it goes unfixed, because the water meter keeps counting whether or not anyone's home. Here's what's actually happening inside the tank, what each fix costs, and how to tell a $15 part from a job that means a whole new toilet.

• Flapper replacement: the most common fix. The flapper is the rubber (or synthetic) seal at the bottom of the tank that lifts when you flush and should drop back down to seal the tank. Over years, mineral deposits, chlorine, and simple age make it warp or stop sealing fully. A basic flapper part costs under $15; a plumber's visit to diagnose and swap it typically runs $100–$200 total.
• Fill valve replacement: the taller assembly that refills the tank after a flush and shuts off at the right water level. When it fails, the toilet either runs continuously or cycles on and off ("phantom flushing") every few minutes as water slowly seeps out and the valve tops the tank back up. Replacement typically runs $100–$250 installed, a bit more than a flapper because the valve connects to the supply line and float mechanism.
• Both at once: many plumbers replace flapper and fill valve together on an older toilet, since both parts wear on a similar timeline and a second trip costs more than doing it once. Expect $150–$350 for the combined job.
• Flush valve or overflow tube crack: less common, but if the entire valve seat at the tank's base is corroded or the plastic overflow tube has cracked, the repair moves toward tank internals replacement, typically $150–$300.

• The toilet rocks or has water pooling at its base. That's a wax ring or flange problem, not a tank issue — see our toilet flange repair guide.
• Water pressure in the house is unusually high. A fill valve that keeps failing every year or two, in a house where other fixtures also act up, can be a symptom of high street pressure rather than a bad part — worth checking with a $15 gauge as described in our water pressure troubleshooting guide.
• The toilet is original to a home built before the mid-1990s. Very old porcelain tanks sometimes have obsolete internal geometry that makes a modern universal fill valve fit poorly. At that point, replacing the whole toilet with a modern low-flow model — covered in our toilet installation cost guide — is often more cost-effective than chasing parts compatibility, and it cuts water use going forward.

Keep reading

• Boiler Replacement Cost in California
• Plumbing Inspection Before Buying a Home
• Earthquake Plumbing Prep
• How Much Does a Plumber Cost in California? 2026 Rates Explained
• California plumbing cost guides