Finding the problem is usually simple
A toilet runs constantly because the fill valve that lets water into the tank isn't closing completely. A toilet runs intermittently because the valve opens slightly for a few minutes. In either case, you have to figure out why that valve isn't stopping the incoming water flow and if there are broken parts of the toilet that need attention.
First, look for leaks. A leak in the tank can make a toilet run constantly or intermittently. If your toilet is leaking, you've probably noticed it already. But take a look just to be sure. If you find leaks coming from the tank bolts or flush valve, you'll most likely have to remove the tank from the bowl so you can replace the tank bolts, the rubber washers and the gaskets on the flush valve. If there are leaks around the fill valve, tighten the locknut (see Photo 6). Leaks can come from cracks in the tank, too. In that case, the only reliable solution is a new toilet.
If you don't find any leaks, lift off the tank cover. At first glance, the array of submerged thingamajigs inside may look intimidating. But don't let them scare you. There are really only two main parts: the flush valve, which lets water gush into the bowl during the flush; and the fill valve, which lets water refill the tank after the flush. When a toilet runs constantly or intermittently, one of these valves is usually at fault.
To determine which valve is causing the trouble, look at the overflow tube. If water is overflowing into the tube, there's a problem with the fill valve. If the water level is below the top of the tube, the flush valve is leaking, allowing water to trickle into the bowl. That slow, constant outflow of water prevents the fill valve from closing completely. We cut away the fronts and backs of new toilets to show you how to replace these parts of the toilet. Your toilet won't look so pristine inside. You'll find scummy surfaces, water stains and corrosion. But don't be squeamish—the water is as clean as the stuff that comes out of your faucets.
Repair the fill valve. Fix 1: Adjust the float
If your valve has a ball that floats at the end of a rod, gently lift the rod and listen. If the water shuts off, you may be able to stop the running by adjusting the float. Some fill valves have a float adjustment screw on top (see Figure A below). If there is no adjustment screw, bend the float arm. If you have a Fluidmaster-style fill valve, make sure it's adjusted properly (Photo 8). You don't have to empty the tank to make these adjustments.
Get to Know the Inside of Your
This cutaway photo highlights the parts of a standard toilet.
Repair the fill valve. Fix 2: Flush the valve
Hard water, debris from old pipes or particles from a break in a city water line can prevent a flush valve from closing completely. Running water through it from the supply line will clear the debris. Photos 1 and 2 show you how to do this on one common type of valve. Even though other valves will look different, the clearing process is similar. However, you may have to remove a few screws on top of the fill valve to remove the cap.
Repair the fill valve. Fix 3: Replace the washer
When you remove the cap to flush out the valve, inspect the washer for wear or cracks. Replacing a bad washer is cheap and easy. But finding the right washer may not be. The most common washers are often available at home centers and hardware stores. Other styles can be hard to find. If you decide to hunt for a washer, remove it and take it to the store to find a match. Plumbers usually replace the whole fill valve rather than hunt for a replacement washer.
Repair the fill valve. Fix 4: If you can't fix the fill valve, replace it
Replacing a fill valve requires only a few basic tools (an adjustable pliers and a pair of scissors) and an hour of your time. A kit containing the type of valve we show here and everything else you need at home centers and hardware stores.
Your first step is to shut off the water. In most cases, you'll have a shutoff valve right next to the toilet coming either through the floor or out of the wall. If you don't have a shutoff, turn off the water supply at the main shutoff valve, where water enters your home. This is a good time to add a shutoff valve next to the toilet or replace one that leaks. This is also a good time to replace the supply line that feeds your toilet (Photo 6). A flexible supply line reinforced with a metal sleeve costs about $7 at home centers and hardware stores. Photos 1 – 8 show how to replace the valve. If the height of your valve is adjustable, set the height before you install the valve (Photo 5). If your valve is a different style from the one we show, check the directions. After mounting the valve (Photo 6), connect the fill tube (Photo 7).
The fill tube squirts water into the overflow tube to refill the toilet bowl. The water that refills the tank gushes from the bottom of the fill valve. When you install the valve and supply lines, turn the nuts finger-tight. Then give each another one-half turn with pliers. When you turn the water supply back on, immediately check for leaks and tighten the nuts a bit more if necessary.
Fix the flush valve
When a flush valve causes a toilet to run, a worn flapper is usually the culprit. But not always. First, look at the chain that raises the flapper. If there's too much slack in the chain, it can tangle up and prevent the flapper from closing firmly. A chain with too little slack can cause trouble too. Photo 3 shows how to set the slack just right.
Next, test the flapper as shown in Photo 1. If extra pressure on the flapper doesn't stop the running noise, water is likely escaping through a cracked or corroded overflow tube. In that case, you have to detach the tank from the bowl and replace the whole flush valve. Since the overflow tube is rarely the cause of a running toilet, we won't cover that repair here.
If pressing down on the flapper stops the noise, the flapper isn't sealing under normal pressure. Turn off the water, flush the toilet to empty the tank and then run your finger around the rim of the flush valve seat. If you feel mineral deposits, clean the flush valve seat with an abrasive sponge or ScotchBrite pad. Don't use anything that might roughen it. If cleaning the flush valve seat doesn't solve the problem, you need to replace the flapper.
Replacing your flapper may require slightly different steps than we show (Photos 2 and 3). Your flapper may screw onto a threaded rod or have a ring that slips over the overflow tube. If you have an unusual flush valve, finding a replacement flapper may be the hardest part of the job. To find a suitable replacement, turn off the water, take the old one with you to the home center or hardware store. (Turn off the water before removing the flapper.) You may not find an identical match, but chances are you'll locate one of the same shape and diameter. If not, try a plumbing supply store (in the Yellow Pages under “Plumbing Supplies”) or search online.
It helps to know the brand and model of your toilet. The brand name is usually on the bowl behind the seat. In some cases, the model or number will be on the underside of the lid or inside the tank. Matching an unusual flapper can become a trial-and-error process. Even professional plumbers sometimes try two or three flappers before they find one that works well.
Replace a broken or corroded toilet flush handle
Toilet flush handles are another part of a toilet that can cause toilets to keep running. Often handles get loose or corroded and no longer pull the flap up or drop it back down properly. It’s an easy repair, but there’s a trick to getting the flush handle out. The retaining nut inside the tank is a reverse thread. So, if you’re in front of the toilet, turn the nut to the left to loosen (Photo 1). Then remove the old handle and lever, slide the new handle into place, and thread on the retaining nut. Tighten by turning to the right (Photo 2).