How to Select and Change a Toilet Flapper

411 plumb Leaking toilet flappers can waste an enormous amount of water without you realizing it. The water goes quietly down the drain often without you noticing the fill valve refilling the toilet then one day you receive the water bill and wonder why it is hundreds of dollars higher than it used to be. Often a flapper costing less than $10 is the culprit. If dye testing reveals a leaking flapper you need to replace it.

Unfortunately it is not a simple matter because there is no universal fits all toilet flapper. Today you are faced with a bewildering array of flappers for different manufacturers and models. Quite a few are proprietary and difficult to get if you are unlucky enough to have a less than popular model. You are also faced with flappers that are for older toilets that allow the entire tank to empty before closing, and flappers that close after allowing a certain amount of water into the bowl before closing.

You will probably need to know the make and model of the toilet as well as whether it is a full flow or, low flow toilet. It is also not a bad idea to shut off the water to the toilet and bring the flapper with you, so that a knowledgeable salesperson can identify the flapper. Researching on line and knowing the manufacturer part number is not a bad idea. Interestingly enough there are also times when the OEM part works best, and others where an aftermarket part manufacturer has a better part, this is an area where a plumbing pro will often have an edge from the experience of replacing many over time and knowing what works best. Another factor in determining if a flapper is good is whether or not the rubber it is made of is resistant to chlorine and chloramines. Those are chemicals that are used in water treatment of municipal water supplies to sanitize the water and keep it safe to drink. They are detrimental to the life of rubber when used in high amounts.

Conventional Flappers

Older toilets before the days of low flow toilets had flappers that allowed the water level to drain completely to the bottom of the tank. Also some low flow toilets use this type of flapper because the flush valve was raised off the bottom of the tank so less water was available, or a device was placed around the flush valve to hold the water back from reaching it. If you were to put a low flow flapper on an older toilet you would probably end up with a toilet that flushes every other flush. Some of the flappers that allow the toilet tank to drain to the level of the flush valve are shown below. There are indeed many more that aren’t shown and if you will note many look very similar but are not interchangeable.

Low Flow Flappers

Low flow flappers are designed to only let part of the contents of the tank to flow into the bowl before closing. Through a variety of designs such as floats that hold the flapper open until the water level drops to the set amount. Or, parts that turn to different positions so an air vent takes longer or shorter amounts of time to allow water into the flapper controlling buoyancy and when the flapper can close. Or, different discs that have differing orifice sizes controlling the speed water can enter into the flapper air camber again controlling the buoyancy and when it is allowed to close. If you put an older style flapper on a modern low flow toilet you will often see the toilet flush multiple times and sometimes the incoming water will actually prevent the contents of the bowl from leaving properly. Some of the more modern low flow toilets have an extra large diameter flapper that allows the water to flow from the tank to the bowl extra fast resulting in an extremely powerful flush. Some of the flappers for low flow toilets are shown below again you will note there are many with subtle differences and also some of them are the large diameter models.

Tank Balls, Flush Discs, and Flush Tower Seals

If  the differences in the flappers I discussed above aren’t enough there are other types of devices other than flappers used to control the flow of water into the bowl such as triple seal tank balls, discs, and seals that screw or snap onto parts that are reused. Some of these are pictured below.

Success is often determined by research and knowledgeable sales persons at where you shop for the parts. Selecting the right part and installing it correctly is the difference between a job well done and failure. When you are finished the toilet should flush one time completely by just pressing and releasing the handle, and not leak water from the tank to the bowl when you are not flushing. If that doesn’t happen something is wrong and you need to fix it.

Posted in How To Plumbing Tips, Toilet Repairs Tagged with: , , , ,
2 comments on “How to Select and Change a Toilet Flapper
  1. A plumber replaced my 10 year old fill valve. Shortly, afterwards, the plastic handle broke so I replaced that myself and adjusted the bar inside that the chain attaches to. Then the toilet would occassionaly keep running which it hadn’t done before. I observed that the flapper didn’t want to always go over the “drain” completely so water would keep running out and the tank wouldn’t fill. So I replaced the flapper with the exact kind and brand (Korky Universal flapper) that was in the tank. It still will occassionally not sit properly. Since it isn’t doing this every time, I’m miffed at what is wrong. Does the chain need adjusting? How so and if it does, why does it work properly sometimes? Do I need to replace the plastic flush valve? The water has always been filtered by a whole house softner and I don’t use any chemicals in the tank so the conditon of the original flapper didn’t look any different than the new one. Can you determine what might be wrong? Thanks! Barbara

    • Redwood says:

      Hi Barbara,
      The flapper you are using mounts with either a ring around the overflow tube or attaches onto two hooks coming off the overflow tube which of the two methods are you using. Sometimes the angle of the chain down to the flapper can have some bearing on how well a flapper rests into place. Sometimes a slight bending of the tank lever is needed to align things better. Plastic tank levers can be bent by warming the plastic with a cigarette lighter moving it rapidly back and forth over a small area until it becomes warm enough to bend and hold it in place while it cools. the chain should have a little bit of slack in it when the flapper is closed. Sometimes the flappers get packaged in a manner that bends the mounting arms, with the mounting arms kinked they don’t hang in place well. A different one may work better. On some of the Kohler toilets the rubber gasket under the flush valve gets puckered up and may be holding the flapper up, trimming the raised part of the gasket with a sharp blade often helps. If one of these solutions doesn’t help more info about the toilet make and model might be needed and perhaps a picture. Let me know.

      BTW a handle breaking is almost always a sign that a old flapper was sticking too hard to the flush valve.

Leave a Reply

Your email address will not be published. Required fields are marked *