How to Fix a Running Toilet

If your toilet will not stop running, you are not alone. A running toilet is one of the most common plumbing problems in Los Angeles homes, and it is also one of the most wasteful. A single running toilet can waste up to 200 gallons of water per day, driving your water bill up by $50 to $100 per month. The good news is that this is almost always a DIY-friendly repair that costs less than $25 in parts.

In this guide, we will walk you through how to diagnose the cause of your running toilet and fix it step by step. No special tools or plumbing experience required.

How a Toilet Works (The Basics)

Before you can fix a running toilet, it helps to understand the three main components inside the tank:

• The flapper — A rubber seal at the bottom of the tank that lifts when you flush and drops back down to seal the tank once flushing is complete. This is the most common cause of a running toilet.
• The fill valve — The tall mechanism on the left side of the tank that refills the tank with water after each flush. It turns on when the water level drops and shuts off when the tank is full.
• The float — A device (either a ball on an arm or a cup that slides along the fill valve) that tells the fill valve when to stop filling. If the float is set too high, water rises above the overflow tube and the toilet runs continuously.

A running toilet means one of these three parts is not working correctly. Let us figure out which one.

Step 1: Diagnose the Problem

Remove the tank lid and set it somewhere safe (they are heavy and fragile). Look inside the tank while the toilet is running and check these three things:

Check 1: The flapper seal

Press down on the flapper with your hand. If the running stops, the flapper is not sealing properly and needs to be replaced. This is the cause about 80 percent of the time.

Check 2: The water level

Look at the overflow tube (the open-topped tube in the center of the tank). If water is flowing into the overflow tube, the water level is set too high. You need to adjust the float.

Check 3: The fill valve

If the flapper seals fine and the water level is correct but the toilet still runs, the fill valve itself may be worn out and needs replacement.

Fix 1: Replace the Flapper

This is the most common fix and the easiest. A replacement flapper costs $5 to $10 at any hardware store.

What you need:

• A new flapper (bring the old one to the store to match the size)
• A towel

Steps:

1. Turn off the water supply valve located behind the toilet near the floor. Turn it clockwise until it stops.
2. Flush the toilet to drain most of the water from the tank.
3. Unhook the old flapper from the two pegs on the overflow tube and disconnect the chain from the flush lever.
4. Wipe the flush valve seat (the ring the flapper sits on) with a cloth to remove any mineral deposits or debris. A dirty seat prevents a proper seal even with a new flapper.
5. Hook the new flapper onto the pegs and connect the chain to the flush lever. The chain should have about half an inch of slack — not too tight and not too loose.
6. Turn the water supply back on and let the tank fill.
7. Flush and watch. The toilet should fill, stop, and stay quiet.

If the new flapper does not solve the problem, move on to the next fix.

Fix 2: Adjust the Float

If water is flowing over the overflow tube, the float is set too high. The water level should sit about one inch below the top of the overflow tube.

For a ball float (older toilets):

• Look for the metal or plastic arm connecting the ball to the fill valve.
• Bend the arm downward slightly to lower the ball. This lowers the point at which the fill valve shuts off.
• Flush and check. Adjust again if needed until the water stops about one inch below the overflow tube.

For a cup float (newer toilets):

• Find the adjustment clip or screw on the float cup that slides along the fill valve shaft.
• Squeeze the clip and slide the cup downward about half an inch.
• Flush and check the water level. Repeat until correct.

Fix 3: Replace the Fill Valve

If the flapper is good and the float is set correctly but the toilet still runs, the fill valve is likely worn out. Replacement fill valves cost $8 to $15 and the job takes about 20 minutes.

What you need:

• A new fill valve (universal models fit most toilets)
• An adjustable wrench or pliers
• A towel and a small bucket or container

Steps:

1. Turn off the water supply and flush the toilet. Use a towel or sponge to soak up remaining water in the tank.
2. Place a bucket or towel under the water supply connection at the bottom of the tank.
3. Disconnect the water supply line from the bottom of the fill valve using your wrench. Some water will drain out.
4. Remove the locknut on the underside of the tank that holds the fill valve in place. Turn it counterclockwise.
5. Lift the old fill valve out of the tank.
6. Adjust the height of the new fill valve so the top sits about one inch above the overflow tube (most have a twist-to-adjust base).
7. Insert the new fill valve into the hole and tighten the locknut from below. Hand-tight plus a quarter turn with pliers is enough — do not overtighten or you may crack the tank.
8. Reconnect the water supply line.
9. Attach the refill tube to the overflow tube (this small hose refills the bowl after flushing).
10. Turn the water on and let the tank fill. Check for leaks at the base connection.

Fix 4: Adjust the Chain Length

Sometimes the fix is even simpler than replacing parts. If the flush chain is too short, it pulls the flapper open slightly and prevents a full seal. If it is too long, it can get caught under the flapper.

• Too short — Move the chain hook to a hole further from the flush lever, or add a few links.
• Too long — Move the hook closer to the lever or trim excess chain with wire cutters. Leave about half an inch of slack.

Parts Cost Summary

Part	Cost	Difficulty
Toilet flapper	$5 – $10	Easy (5 minutes)
Float adjustment	Free	Easy (2 minutes)
Fill valve	$8 – $15	Moderate (20 minutes)
Complete repair kit	$20 – $25	Moderate (30 minutes)

When to Call a Professional in Los Angeles

Most running toilet problems are straightforward DIY fixes. But there are situations where calling a professional makes more sense:

• The toilet runs even after replacing the flapper and fill valve — The flush valve seat may be cracked or warped, which requires removing the entire toilet.
• You see water on the floor around the toilet base — This could indicate a failed wax ring seal, which is a different (and messier) repair.
• The toilet is old and parts are hard to find — Some older toilet models use non-standard parts. A handyman can assess whether repair or replacement makes more sense.
• You are not comfortable working with plumbing — There is no shame in hiring a pro. A simple repair done wrong can cause water damage that costs thousands.

At GoldKey Repairs, we handle running toilet repairs and all types of plumbing work for Los Angeles homeowners. Our pricing is transparent: $150 for the first hour and $85 for each additional hour, plus the cost of parts. Most running toilet repairs take less than an hour. Call us at (323) 630-9115 to schedule a visit.