How to Fix a Running Toilet (and When to Call a Handyman)

Lift the lid off the tank and you will see a simple system. When you press the handle, a chain lifts the flapper, a rubber seal at the bottom of the tank. Water rushes from the tank into the bowl and the flush happens. As the tank empties, the flapper drops back down and seals the opening again.

At the same time, the fill valve (the tall part on one side, usually with a float attached) senses that the water level dropped and starts refilling the tank. When the float rises to the set level, the fill valve shuts off. The overflow tube in the middle is a safety drain: if the water ever rises too high, it spills into that tube and down into the bowl instead of onto your floor.

A toilet runs when one of these steps does not finish. Either the flapper is not sealing, so water keeps leaking into the bowl, or the fill valve is not shutting off, so water keeps spilling into the overflow tube. Figuring out which one is your problem is the whole game.

Start by looking at the water level in the tank. If the water is up at the top of the overflow tube and you can see it trickling in, the fill valve is the problem. The tank is overfilling and the extra water is draining into the bowl through the overflow.

If the water level is below the overflow tube but the toilet still refills on its own every so often (people call this a phantom flush), the flapper is the likely culprit. Water is leaking past the seal, the level drops, and the fill valve kicks on to top it up.

To confirm a flapper leak, try the dye test. Put a few drops of food coloring in the tank, do not flush, and wait 15 to 20 minutes. If color shows up in the bowl, water is getting past the flapper. Also check the chain: a chain that is too short holds the flapper slightly open, and a chain that is too long can get trapped under the seal.

Flappers are rubber, and rubber wears out. Over the years it warps, hardens or picks up mineral deposits that keep it from sitting flat. San Diego tap water tends to be on the hard side, so scale buildup on the flapper and the valve seat is a common reason toilets start running here.

First, turn off the water at the shutoff valve behind the toilet (turn it clockwise) and flush to empty the tank. Wipe the flapper and the round seat it sits on. Sometimes a gentle scrub with a soft pad removes enough buildup to stop the leak. If the flapper feels stiff, cracked or out of shape, replace it.

Replacement flappers are inexpensive and sold at any hardware store. Take the old one with you, or note the brand and the size of the flush opening (2 inch and 3 inch are the common sizes). Unhook the old flapper from the ears on the overflow tube, clip on the new one, attach the chain with just a little slack (about half an inch), turn the water back on and test. Run the dye test again to make sure the seal holds.

If water is running into the overflow tube, try lowering the water level first. On most modern fill valves, you turn an adjustment screw or slide a clip on the float rod to make the float sit lower. On older toilets with a ball float on an arm, you can gently bend the arm down or turn the screw on top of the valve. The goal is a water level about an inch below the top of the overflow tube, or at the line marked inside the tank.

If adjusting does not stop it, or the fill valve hisses, refills slowly or does not shut off at all, it is time to replace it. A universal fill valve kit fits most toilets. Shut off the water, flush, sponge out the leftover water, disconnect the supply line under the tank, unscrew the lock nut and lift the old valve out. Set the new valve height to match your tank, tighten the lock nut by hand plus a small turn, reconnect the supply line and clip the refill tube onto the overflow tube.

Turn the water on slowly and watch for drips under the tank. A small leak at the connection usually means the nut needs a quarter turn more. Do not overtighten plastic parts; they crack.

A handle that sticks can hold the flapper open after a flush. If jiggling the handle stops the running, check whether the handle nut inside the tank is loose or the lever arm is rubbing against the tank lid or wall. Tighten or replace the handle assembly.

A cracked overflow tube will let water drain constantly, and that usually means replacing the flush valve, which involves separating the tank from the bowl. Same with a worn tank to bowl gasket that drips onto the floor. These jobs are doable for a confident DIYer, but they take longer and there is more to go wrong.

Finally, check the supply line and the shutoff valve themselves. Old braided lines and corroded shutoff valves can drip or fail when you turn them. If your shutoff will not turn or leaks when you touch it, stop and get help before something breaks.

If you do it yourself, parts for a flapper or a fill valve usually run somewhere around 10 to 30 dollars at a hardware store. A full tank rebuild kit with flapper, fill valve and gaskets usually costs more, but still well under the price of a new toilet.

If you hire it out, most homeowners pay somewhere in the range of roughly 100 to 300 dollars for a typical running toilet repair, depending on the part, the toilet model, travel and how much work is involved. A flush valve or tank to bowl gasket job usually lands toward the higher end because the tank has to come off. These are general market ranges, not a quote, and prices vary across San Diego County.

Since a constant leak keeps costing you on the water bill, a quick repair usually pays for itself. If you are not sure what your job involves, Handmax can give you a free quote if you text a photo of the inside of the tank.

Call for help if the shutoff valve is stuck or leaking, if water is coming from under the toilet or the base, if the tank is cracked, or if you replaced the flapper and fill valve and it still runs. Also call if the toilet rocks on the floor, since a loose toilet can break the wax seal and leak into the subfloor.

A handyman is a good fit for these small repairs and like-for-like part swaps. Work that changes your plumbing, moves a drain or needs a permit is a job for a licensed plumber. In California, an unlicensed handyman can only take on small jobs under 1,000 dollars in total that do not need a permit, so for anything bigger, ask about licensing up front.

If your toilet is running right now and you would rather not deal with it, Handmax offers same-day appointments in many cases around San Diego, Chula Vista, El Cajon, La Mesa and nearby. Text a photo of the tank and you will usually get an answer within the hour.