Rogue Plumber:

Replacing A Toilet Flapper Valve...
And Fixing The Low-Flow Toilet Blues

In This Article:

We replace an old Kohler toilet flush valve with a new Kohler low-flow flapper valve that turns out to be rather adjustable

Related Articles:
Skill Level: 1-2 (Basic) Time Taken: 15 Minutes

By , Editor


I was asked to fix a toilet that was running constantly.

There are two valves in a typical toilet, so there are two main reasons that a toilet runs constantly:

  1. The fill valve can leak and let water into the tank. The excess water will drip down the overflow tube into the bowl. With this problem you can typically hear the water just barely trickling, but trickling almost continuously.
  2. The flush valve can leak and let water drain into the bowl. When this happens the water level in the tank will drop, and the fill valve will open periodically, filling the tank again.

This toilet had a leaky flush valve. I could tell right away because the water level was an inch below the overflow tube (as it should be), yet I could see ripples in the water in the bowl. The water level in the tank would drop slowly, then the fill valve would open for a few seconds and I could hear water running.

The Fix For A Constantly-Running Toilet:

The first thing I did was shut off the water supply to the toilet.

Then I flushed the toilet to get the water out of the tank.

I arrived at this house with only a minimal amount of tools, and none of the lighting equipment I carry on major projects, so some of these photos are rather dark or grainy.

In The Tank:

  • 1. The Flush Lever. This lever is raised up when the toilet is flushed.
  • 2. The Flush Valve, or flapper valve.


The flush valve is actuated by a chain that hooks onto the flush lever. I removed this hook.


Then I reached down inside the tank and lifted the flapper valve off its mounting tabs. Many toilets use an all-rubber flapper valve, which comes off quite easily. This hard plastic flapper required more effort... in fact, I thought that I might break something.


I examined the underside of the flapper valve, just for kicks. Whenever I make a repair I like to confirm what is wrong.

It looked like the flapper might not have been seating perfectly at one spot (red arrow).


The flapper seals against the valve seat (arrow). I checked this seat to make sure there was no buildup of mineral deposits, which could cause this problem.

At this point I headed to the nearest hardware store to buy a simple all-rubber flapper valve, which usually costs about $2 to $4. Being a bit lazy, I decided instead to go to a local plumbing and heating supply store. I figured it might cost a couple of bucks more, but their store was closer.

The New And Improved Flapper Valve:

There can be some big advantages to buying supplies at the locally-owned, professional-oriented stores.

As soon as I pulled the old flapper valve from my pocket the man at the store knew exactly what type of toilet I was fixing. He recognized the part as belonging to an early Kohler low-flow toilet.

He showed me this new-and-improved flush valve that comes with new Kohler toilets. Right away I realized something. I asked if the Styrofoam float was adjustable. He nodded. He explained that if the float was placed lower on the chain, that the flapper would stay open longer, and if the float was placed higher, the flapper would close even earlier. 

As you may recall, the Environmental Protection Agency forced some changes on the plumbing industry back in the early 1990's. In an attempt to conserve our resources, the EPA now requires that all toilets sold in the United States use only 1.6 gallons per flush (GPF), instead of the previous standard of 3.5 gallons per flush.

To comply with this rule, many toilet manufacturers modified their flush valves to close prematurely. Instead of the whole tank of water surging into the bowl, less than half of the tank would empty out. But that simple change has not worked well for many toilets. Millions of Americans have been irritated by toilets that don't flush on the first attempt. Having to flush 2 or 3 times to clear the bowl is hardly a wise way to reduce water consumption.

A lot of Americans have been annoyed by the government's high-handed approach to something that affects us so personally. Many parts of the country do not face any shortages of water. Besides, the biggest culprit in water waste is lawn sprinkling. If you really want to save water, then don't pamper your lawn.


It turns out there are some sneaky, low-down, possibly illegal ways to make a low-flow toilet work properly. With this type of flapper valve, the plastic retainer clips can be removed and the float moved downhill to a lower position.


Like this.

When the float is placed lower on the chain, it will hold the flapper open longer, letting more water flow into the bowl.

With most low-flow toilets, restoring the flow closer to the original 3.5 gallons per flush seems to make them flush better, which is logical since many 1.6 GPF toilets are just 3.5 GPF toilets with a slight modification.


After the flapper valve was installed, I noticed that the chain was too long. I was about to cut the chain shorter with a pair of wire cutters...


...when I noticed that the flush lever had a little socket for this type of chain.


So I just snapped the chain into the socket and wrapped the excess chain around the lever so it would not get caught on something.


It's hard to see the action of moving water in a photograph, but the float is holding the flapper open even though the water is almost gone from the tank. With the original part, the flapper closed when the water was about 4 inches higher. 

I recently installed a low-flow toilet made by Eljer that made me stop and think. It looked like they had simply made a hole in an otherwise ordinary hollow flapper valve, so some of the air would escape when the flapper was raised. Then the flapper would lose its buoyancy and fall back prematurely, covering the big opening that lets water rush into the bowl.

It occurred to me that replacing this flapper with an ordinary replacement flapper (which would not have any little vent hole) would restore the toilet back to its original 3.5 gallon per flush design. I also noticed that Home Depot sells a couple of different toilet flapper valves that are adjustable, so the homeowner can try different settings to get one that works best and still conserves some water.

Oh, lookey here...

The new Kohler toilet that I installed in my own home a couple of years ago uses the same foam float as in this article. I noticed that I could also adjust the float height as described earlier.

But this toilet (the model is called Portrait, and it's pretty expensive, about $250) works fine with the float in the original setting, so I'll leave it for now.

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Copyright 2002, 2005

Written February 4, 2002
Revised October 19, 2007