Why is my toilet constantly running and how to fix it

A toilet that keeps running is almost always losing water past a worn flapper or a fill valve that will not shut off, and both parts cost under $25 at any Sioux Falls hardware store. You can stop the water waste today with a five-minute diagnosis and a screwdriver. This post walks through the exact causes, the parts involved, what a running toilet costs you every month in Sioux Falls, and the point where a plumber is the cheaper call.

We are Emergency Plumbing Sioux Falls, and we fix running toilets across the city every week. Most of them are the same three parts.

Why is my toilet constantly running in Sioux Falls SD?

A toilet constantly running in Sioux Falls SD is caused by water escaping the tank into the bowl after the flush cycle ends, which forces the fill valve to keep refilling a tank that never reaches its shutoff level. There are only four parts that can do this, and three of them fail from normal wear.

Here is what is actually happening inside the tank:

• Flapper - the rubber seal at the bottom of the tank. It hardens, warps, or mineral-crusts and no longer seats. Water bleeds into the bowl 24/7.
• Fill valve - the tall plastic tower. When the diaphragm inside wears out, it never fully closes and you hear a constant hiss.
• Flush valve seat - the plastic or brass opening the flapper presses against. A nick or mineral buildup means even a new flapper will not seal.
• Overflow tube or refill tube - if the refill tube is pushed down into the overflow, water siphons straight into the bowl.

Sioux Falls water runs hard. Our municipal supply pulls from the Big Sioux aquifer and the Missouri River, and it carries enough dissolved calcium and magnesium that scale builds on rubber and plastic parts faster than in softer-water cities. That is why flappers here tend to fail in three to five years instead of the seven to ten you read about online. If your home has never had a water softener installation Sioux Falls SD, expect the shorter end of that range.

How to diagnose a running toilet in five minutes

Diagnosing a running toilet in Sioux Falls takes about five minutes and one food-coloring test, and the result tells you exactly which part to replace. Do this before you buy anything.

1. Lift the tank lid and set it somewhere safe. Tank lids crack easily on tile.
2. Drop six to eight drops of food coloring into the tank water. Red or blue works best.
3. Wait 10 minutes. Do not flush.
4. Look in the bowl. If color appears, the flapper or flush valve seat is leaking. If the bowl stays clear, the fill valve is the problem.
5. Listen. A steady hiss means the fill valve is running. A periodic short refill every 20 to 30 minutes means the flapper is seeping.

One more check: grab the flapper and run your thumb along its edge. If it feels stiff, chalky, or has visible grit, that is your culprit. A flapper that still feels soft and pliable but leaks is usually sitting on a scaled valve seat.

How do I fix a constantly running toilet in Sioux Falls South Dakota?

You fix a constantly running toilet in Sioux Falls South Dakota by replacing the failed part - the flapper first, then the fill valve if the hiss continues - and both jobs take under 30 minutes with basic hand tools. Shut the water off at the angle stop behind the toilet before you start.

Toilet flapper replacement Sioux Falls SD

This is the fix in roughly seven out of ten running toilets we see. Kits run $8 to $15 at any Sioux Falls hardware store.

1. Turn the angle stop clockwise until it stops. Flush the toilet to drain the tank.
2. Unhook the flapper chain from the flush lever arm.
3. Slide the old flapper off the overflow tube posts. Note the brand - Korky, Fluidmaster, and Toto use different mounts.
4. Take the old flapper to the store with you. Matching the brand and model prevents a second trip.
5. Install the new flapper, leaving about half an inch of slack in the chain. Too tight and it leaks; too loose and it will not lift.
6. Turn the water back on and do the food-coloring test again.

Toilet fill valve repair Sioux Falls South Dakota

If the bowl stays clear but the tank keeps hissing, the fill valve is done. A replacement runs $12 to $20 and takes about 20 minutes.

1. Shut off the angle stop and flush the tank empty. Sponge out the last inch of water.
2. Disconnect the supply line from the bottom of the tank with an adjustable wrench.
3. Loosen the lock nut under the tank and pull the old valve out from inside.
4. Drop the new valve in, set it so the critical level mark sits one inch above the overflow tube, and tighten the nut hand-tight plus a quarter turn.
5. Reconnect the supply line, turn the water on, and adjust the float so the tank fills to the marked water line - usually one inch below the top of the overflow tube.

If you have done both and the toilet still runs, the flush valve seat is damaged or the tank-to-bowl gasket is failing. That is a bigger job, and it is where most homeowners call us. Our toilet repair Sioux Falls SD techs carry every common flapper and valve on the truck, so it is a one-visit fix.

What a running toilet costs you every month

A running toilet wastes between 200 and 4,000 gallons of water per day depending on how badly the flapper is leaking, which at Sioux Falls water rates adds roughly $15 to $200 to your monthly bill. The EPA puts the common middle case - a steady silent leak - at about 200 gallons a day, or 6,000 gallons a month.

Sioux Falls utilities bill water and sewer together, and you pay sewer on every gallon that goes down the drain. That is the part people miss. A leak that costs $30 in water often adds $40 or more in sewer charges.

Here is what a running toilet typically costs to fix in Sioux Falls in 2026:

• DIY flapper or fill valve: $8 to $20 in parts, 20 to 30 minutes.
• Professional flapper or fill valve replacement: $95 to $185, parts and labor.
• Full toilet rebuild (flapper, fill valve, flush valve seat, gaskets, supply line): $175 to $325.
• New toilet installed if the bowl or tank is cracked: $275 to $650 depending on the model.

If the toilet is 20 years old, running constantly, and the bowl is scratched or the tank is sweating, replacement usually beats a rebuild. We install toilet installation Sioux Falls SD with a new wax ring, new supply line, and haul-away of the old unit included.

Common mistakes we see on DIY toilet repairs

The most common mistake on a running toilet repair in Sioux Falls is replacing the flapper without cleaning the valve seat underneath it, which means the new flapper leaks within a week. We get called back to that exact situation constantly.

Watch for these:

• Not shutting off the angle stop first. If the valve is frozen or weeping, you now have two problems. Test it before you start.
• Buying a universal flapper for a brand-specific toilet. A generic flapper on a Toto or Kohler tank will not seal correctly.
• Over-tightening the fill valve lock nut. Hand-tight plus a quarter turn. Crank it and you will crack the tank.
• Setting the float too high. Water then runs into the overflow tube continuously - you have created a new running toilet.
• Ignoring a warped tank-to-bowl gasket. If water runs down the outside of the bowl, that gasket is the problem, not the flapper.
• Letting the chain kink. A tangled chain holds the flapper open a quarter inch and you will hear it running all night.

One more: if your toilet runs only in winter, the issue may be a frozen or sweating supply line rather than the tank parts. That is a different repair, and our leak detection and repair Sioux Falls SD team handles it the same day.

When to call a professional

Call a plumber when you have replaced the flapper and fill valve and the toilet still runs, when water is pooling on the floor around the base, or when the shutoff valve behind the toilet will not close. Those three situations move past a $15 parts job into real water damage.

We also get calls when the toilet is the symptom, not the problem. A toilet that gurgles and refills on its own every hour is often a venting or drain issue, not a tank issue. If you are also seeing slow drains in the tub or a sewer smell in the basement, the running toilet is a side effect of a blocked line, and our drain cleaning Sioux Falls SD crew needs to clear it before the toilet will behave.

Our technicians are state-licensed plumbing contractors. We quote the repair before we start, we carry the common parts on the truck, and we test the flush twice before we leave. If the toilet is beyond saving, we will tell you that instead of selling you a rebuild you do not need.

Frequently Asked Questions

Why does my toilet keep running in Sioux Falls SD?

Almost always a worn flapper or a failing fill valve. Sioux Falls water is hard, so mineral scale wears these rubber and plastic parts out in three to five years instead of the seven to ten typical in softer-water cities. A food-coloring test in the tank tells you which one it is in about 10 minutes.

How do I fix a constantly running toilet in Sioux Falls South Dakota?

Shut off the angle stop, drain the tank, and replace the flapper first - that solves roughly 70 percent of cases for $8 to $15. If the tank still hisses, replace the fill valve for another $12 to $20. Both jobs take under 30 minutes. If it still runs after that, the flush valve seat or tank gasket is the issue.

How much does it cost to fix a running toilet in Sioux Falls?

DIY parts run $8 to $20. Professional flapper or fill valve replacement in Sioux Falls in 2026 runs $95 to $185 with parts and labor. A full toilet rebuild with all new internals is $175 to $325. Replacing the toilet entirely is $275 to $650 installed.

Should I replace the flapper or the whole toilet in Sioux Falls SD?

Replace the flapper if the toilet is under 15 years old and the porcelain is sound. Replace the whole toilet if the tank or bowl is cracked, the base is leaking onto the floor, the bowl is badly scratched, or the toilet is 20-plus years old and you have already rebuilt it once.

How much water does a running toilet waste?

A silent flapper leak wastes about 200 gallons a day - 6,000 gallons a month - according to the EPA. A fully open flapper can push 4,000 gallons a day. In Sioux Falls you pay sewer charges on every one of those gallons, so the bill impact is roughly double the water charge alone.

Get help with Plumbing in Sioux Falls

If your toilet is still running after a flapper and fill valve swap, or you would rather not spend your Saturday with a wrench, we can have it fixed today. Emergency Plumbing Sioux Falls handles running toilets, rebuilds, and full replacements across the city, with upfront pricing before we start.

Call +1 (713) 655-1138 and we will get your water bill back to normal.