My toilet ran for three weeks before I finally dealt with it. Three weeks of that soft, whispery hiss every time I walked past the bathroom. I kept telling myself I’d get to it. I kept not getting to it. Then my water bill arrived and I nearly choked on my coffee — up $31 from the previous month, just from one lazy toilet valve.
Here’s the thing nobody tells you upfront: a running toilet is almost always the same three-part problem. Not twelve parts. Not a mysterious plumbing situation requiring a guy named Dale with a work van. Just three inexpensive pieces you can grab at any hardware store — Home Depot, Ace, Menards, doesn’t matter — for under $20 combined. And the whole fix takes less time than a sitcom episode.
What’s Actually Happening Inside Your Tank
Before you touch anything, it helps to know what you’re dealing with. Pull the tank lid off and set it somewhere safe. What you’ll see looks complicated. It isn’t.
Your toilet has three jobs: fill with water, stop filling when it’s full, and flush when you ask it to. The flapper (that rubber flap at the bottom) seals the tank. The fill valve refills the tank after a flush. And the float tells the fill valve when to stop. When your toilet runs nonstop, at least one of these three things has quit working properly. The flapper is usually the culprit. maybe 70% of the time, in my experience, but we’re replacing all three while we’re in there, because the parts cost almost nothing and doing it once beats doing it twice.
The Three Parts You Need (and What They Cost)
Go to any hardware store and ask for these three things, or just find them in the plumbing aisle.
A universal flapper: usually $4–$6. Korky and Fluidmaster both make solid ones. I’ve used Korky 2030BP for years without complaint.
A fill valve: the Fluidmaster 400A is the standard, costs about $9–$11, and fits virtually every toilet made since the late 1980s. It comes with instructions that are actually readable, which is a minor miracle in the hardware world.
A float ball or float cup: this sometimes comes integrated with the fill valve kit. If yours does, you’re done shopping. If not, a replacement float cup runs about $4 on its own.
Total damage: somewhere between $13 and $20, depending on your store and whether parts are bundled. Compare that to a plumber’s minimum service call, which in most cities runs $125–$175 just to show up.
Shut Off the Water First.
Seriously.
This sounds obvious. And yet.
The shutoff valve is on the wall behind your toilet, near the floor. small oval handle, usually chrome. Turn it clockwise until it stops. Then flush the toilet once to drain most of the water from the tank. Grab an old towel and put it on the floor under the tank. Some water will drip. That’s fine.
Now sponge out whatever’s left in the bottom of the tank. A cheap dollar-store sponge works perfectly. You want the tank as dry as possible before you start pulling things out.
Replacing the Flapper (Start Here)
The flapper hooks onto two little pegs on either side of the overflow tube, that tall plastic pipe in the middle of your tank. It also connects to the flush handle via a small chain.
Unhook the chain from the handle arm. Slide the flapper ears off the pegs. Done. It takes about 45 seconds.
Snap your new Korky flapper onto the same two pegs. Reattach the chain to the handle arm, leaving about half an inch of slack. Too tight and the flapper won’t seat properly. Too loose and it’ll get sucked under. Half an inch of slack is the sweet spot I keep coming back to after years of fiddling with this.
Swapping Out the Fill Valve
The fill valve is the taller assembly, usually on the left side of the tank. Disconnect the water supply line from the bottom of the tank (it’s just hand-tight usually, or a quick turn with pliers). Then reach under the tank and unscrew the locking nut that holds the fill valve in place. Pull the old valve straight up and out.
Drop the new Fluidmaster 400A into the same hole. The instructions show you how to adjust the height. you want the critical water level mark about an inch below the top of the overflow tube. Tighten the locking nut underneath (hand-tight, then a quarter turn with pliers, don’t over-crank it, or you risk cracking the tank). Reconnect your supply line.
Setting the Float Correctly
If your fill valve came with an integrated float cup, adjusting it is just a matter of pinching and sliding the float up or down on the valve shaft. You want the water to stop filling about one inch below the top of the overflow tube. That’s the line. Too high and water spills into the overflow and your toilet runs constantly. Too low and your flushes feel weak and unsatisfying.
Turn your shutoff valve back on slowly. Watch the tank fill. When it stops, check where the water level lands. Adjust the float if you need to. Flush once, watch it refill, and listen. That hissing sound should be gone.
What Most Guides Get Wrong
Most how-to articles tell you to diagnose the exact broken part first, then only replace that one thing. Logical, right? But here’s my honest take: when you’re already elbow-deep in a toilet tank, and the parts collectively cost less than a decent lunch, replacing all three at once is just smarter. You eliminate the whole system of failure in one visit. You don’t find yourself back at the hardware store in six months when the fill valve. which you didn’t replace, finally gives out.
I’ve done this exact job maybe a dozen times across two houses and one cabin I help maintain for a family friend. The whole process, including cleanup, runs about 18 minutes when you’re not rushing. Your water bill will thank you immediately.
FAQ
Will these parts fit my toilet?
Almost certainly yes. Fluidmaster 400A and Korky 2030BP are both designed as universal fits. The only common exception is older low-profile tanks, but even those usually accept standard parts.
What if the toilet is still running after I replace everything?
Check the flapper chain first. if it’s catching under the flapper, it’ll hold it open slightly. Also confirm the water level sits at least an inch below the overflow tube. Those two things account for probably 90% of post-repair running.
Do I need any special tools?
No. Your hands and one pair of adjustable pliers are genuinely all you need. I do this job in under 20 minutes without reaching for anything else.
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