A running toilet is one of those plumbing problems that is easy to put off because it does not look like an emergency. But a toilet that runs continuously can waste 200 gallons of water per day at San Diego’s January 2026 rate increase of 14.7%, that is a real dollar amount showing up on your next bill every single month you ignore it. Some running toilet fixes take five minutes and cost nothing. Others need a licensed plumber. Here is how to tell which situation you are in.

The Most Common Cause: Faulty Flapper (DIY)

Take the lid off the tank and watch what is happening inside. If water is quietly trickling into the bowl and you can hear that thin, constant running sound, the flapper is almost certainly the culprit. The flapper is the rubber seal at the bottom of the tank that lifts when you flush and reseats to hold water in the tank between flushes. Over time, rubber flappers warp, crack, or accumulate mineral deposits that prevent a clean seal.

A replacement flapper costs $5 to $15 at any hardware store and installs in under 10 minutes no tools needed. Turn off the water supply valve behind the toilet, flush to empty the tank, unhook the old flapper chain from the flush lever and pull the flapper off its mounting posts, snap the new one on, reconnect the chain with a small amount of slack, and turn the water back on. If the running stops, you are done.

Float Adjustment: Also DIY

If the water level in the tank is above the overflow tube the tall open tube in the center of the tank — water is draining into it continuously and running into the bowl. This means the float, which controls when the fill valve shuts off, is set too high. On a ball-float style, bend the arm slightly downward. On a cup-float style, turn the adjustment screw on the fill valve counterclockwise. The water level should be about one inch below the top of the overflow tube.

When to Call a Plumber: Fill Valve Failure

If adjusting the float does not stop the running, or if you hear a constant hissing from the tank even when the water level looks correct, the fill valve itself has likely failed. This is still a manageable repair, but it involves replacing a component that is under water pressure and needs to be done correctly to avoid a flood in the tank area. Most licensed plumbers complete a fill valve replacement in under 30 minutes.

When to Call a Plumber: Toilet Replacement Conversation

If your toilet is over 20 years old and has needed two or more repairs in the past few years, it is worth pricing out a full toilet replacement. Modern low-flow toilets use 1.28 gallons per flush or less, compared to 3.5 to 7 gallons for pre-1994 models. In San Diego, where water costs hit a new record in 2026, upgrading an old toilet pays for itself faster than most homeowners expect.

Not sure what is going on inside your tank?

Call PlumbTech at 1-800-388-8149. Our licensed San Diego plumbers handle everything from a quick fill valve swap to a full toilet repair and replacement fast, affordable, and done right. Book online here.

One More Sign That Needs a Plumber: Water on the Floor

If you notice water pooling at the base of the toilet — not condensation, but actual wetness that stays there — the wax ring seal between the toilet base and the floor flange may have failed. This is not a DIY repair. A failed wax ring means sewer gas can enter the bathroom, and water is seeping under the floor with every flush. PlumbTech handles this as part of standard toilet repair services across San Diego.

Running toilet wasting water every day?

Email Plumbtech.pros@gmail.com or call 1-800-388-8149 and we will get it sorted same day, upfront pricing, no surprises. Schedule your visit here.

Frequently Asked Questions

How much water does a running toilet waste per day?

• A continuously running toilet wastes roughly 200 gallons per day on average — that is about 6,000 gallons per month. At current San Diego water rates, that adds $ or more to your monthly bill depending on your usage tier.

How do I know if it’s the flapper vs. the fill valve?

• Put a few drops of food coloring in the tank and do not flush for 15 minutes. If color appears in the bowl, the flapper is leaking. If the tank is overflowing into the overflow tube despite the water level being correct, the fill valve is the issue.

Can a running toilet cause a water bill spike in San Diego?

• Yes and it is one of the most common culprits behind unexplained bill increases. The City of San Diego specifically lists running toilets as a top cause of unexpected usage spikes. Always check the toilet first when your bill jumps without explanation.