Conventional 3.5 gal/flush toilet with diaphragm fill valve and tank ball flush valve

  • Replace your toilets that have flush rates greater than 1.6 gal/flush with toilets that have flush rates of 1.6 gal/flush or less. Almost all toilets installed from between the mid 1970’s to 1993 have a flush rate of 3.5 gal/flush, and most of the toilets installed before the mid 1970’s have flush rates greater than 3.5 gal/flush. Toilets that are 1.6 gal/flush have tanks that appear small. Your toilets that have typical-size tanks are 3.5 gal/flush, and if the tanks appear large and old-fashioned they are about 5.5 gal/flush. To determine the flush rate of a toilet, close its shut off valve, flush the toilet, fill the tank from a bucket, and check how many gallons it took.

3.5 gal/ flush toilet 1.6 gal/flush toilet

The simplest way to estimate how much you would save by replacing your toilets is to assume that they use 40% of the water used in your home. In most homes, the toilets use less than 40%, so assuming this percentage may be the most you could save. If you replace 3.5 gal/flush toilets with 1.6 gal/flush toilets, 54% of the water will be saved. Check the water bill for the cost of water used each month. If you assume that 40% of this is due to the toilets, multiply: (cost of the water) x 0.40 x 0.54=savings per month. If, for example, your family spends $400 per year for water, the toilets may use about $160 per year and you may save about $88 per year.

Your savings can be estimated more accurately in another way. Assume that each person in the household flushes the toilet five times per day. This is average but you may choose to use a higher or lower figure. If all of your toilets are 3.5 gal/flush and you replace them with toilets that are 1.6 gal/flush, 9.5 gallons would be saved each day, for each person, or 3467 gallons per year per person. Multiply this by your cost of water per gallon to estimate your savings.

If you have no utility sink and you must pour the rinse water from mopping the floor into a toilet, it may not be advisable to replace this toilet with a 1.6 gal/flush model, because they become clogged more easily. 1.6 gal/flush toilets sold in home centers start in price at about $100. To select a toilet, see Appendix A, “Selecting a Toilet”. To install a toilet, see Appendix B, “How to Install a Toilet”.

  • On each toilet, check if the water level in the tank is at the top of the overflow tube and water is flowing into the tube. If you hear a toilet running constantly this will be the problem, but normally you won’t hear it. If water is flowing into the tube, the fill valve is not stopping the water from entering the tank as it is designed to do. Sometimes you can correct the problem by adjusting the fill valve to shut off the water at a lower water level, but sometimes you must repair it or replace it. All toilets have fill valves. A fill valve that has a float ball on an arm is normally called a “ballcock” (there are plunger-valve ballcocks and diaphragm ballcocks).

When you flush a toilet you open the flush valve on the bottom of the tank, allowing the water to drain out. The fill valve senses the water level, and opens when the tank is empty and closes when the tank becomes full. One type of fill valve has a plastic float cup that slides up and down a plastic pipe, to sense if the tank is empty or full. This is called a “float cup fill valve”. On some models you set the water level at which it closes by squeezing the spring clip and raising or lowering the float cup. On other models you turn a large plastic screw. Adjust the fill valve to lower the water level; if this doesn’t fix the problem repair the fill valve. First, replace the “seal”. This is a small rubber diaphragm that stops the water by pressing against a ring of plastic at the top of the valve body. Unscrew the top piece from the fill valve; the seal is in it. Seals for Fluidmaster™ float cup fill valves are available at home centers and hardware stores. If you find grit on the seal, this may be the cause of the problem. Just clean off the grit. Grit can enter a fill valve when you close and re-open the main shut off valve, or when work is done on a nearby water main. If replacing the seal does not repair the fill valve, the ring of plastic is damaged and the fill valve must be replaced. If you replace it with a fill valve of the same brand you do not need to remove the entire fill valve, only the upper part. Float cup fill valves have a lower part that is inserted into an upper part. First, turn off the water to the toilet. Slide up the plastic retainer ring at the bottom of the upper part, and replace the upper part.

Adjusting the float cup Removing the seal from

on a float cup fill valve a Fluidmaster™ float cup valve.

Fluidmaster™ float cup fill valve seal Upper and lower parts of float cup fill valve

Plunger-valve ballcock

Another type of fill valve, the”plunger valve ballcock”, has a rod that is raised by a large floating ball as the tank fills. These are solid brass, and most are very old. The rod pushes a plunger, which shuts off the water. You can adjust it to close at a lower water level by bending the rod downward. If it must be repaired, usually the washer at the bottom of the plunger has worn out. Occasionally, the cause of the problem is that water has leaked into the float ball. To check for this, remove the float ball and shake it.

To repair a plunger valve ballcock, shut off the water to the toilet, remove the plunger, and replace the washer. Replace the other rubber parts if they are available, but these don’t shut off the water, they stop water from leaking out of the ballcock while the tank is filling. The washer and other rubber parts are probably only available at plumbing supply stores and some large hardware stores.

A third type, called a “diaphragm ballcock” also has a rod that is raised by a large floating ball. The rod puts pressure on a diaphragm to shut off the water. These can be adjusted to lower the water level at which they close by turning an adjustment screw on the top. To repair one, you usually only must replace the diaphragm. Shut off the water to the toilet and remove the top piece from the diaphragm ballcock. If you find grit on the diaphragm, this may be the cause of the problem. Just clean off the grit. Grit can enter a fill valve when you close and re-open the main shut off valve, or when work is done on a nearby water main. Occasionally, the cause of the problem is that water has leaked into the float ball. To check for this, remove the float ball and shake it.

Diaphragm ballcock

Another type is the cartridge, or floatless fill valve. A diaphragm senses the water level to open or close the fill valve. They can be adjusted by turning an adjustment screw, but they cannot be repaired.

Cartridge fill valve

Seals, washers and diaphragms are available wherever toilet parts are sold. However, plumbing supply stores and some large hardware stores have a much better selection than home centers, especially for parts for old toilets. Some rubber replacement parts are designed for only one brand and some are universal. If you don’t know the brand, shut off the water to the toilet, remove the part and take it to a store to match it. If your fill valve cannot be repaired you can replace it with any other type and any brand. Float cup fill valves are probably the best choice for two-piece toilets because they are the least expensive, reliable, and their repair parts are easy to find in stores. If you must replace a fill valve, you could install one that is designed to warn you when water leaks out of the tank. These don’t open to let the tank fill when the tank water level becomes low unless you have just flushed the toilet. Different brands are sold in some hardware stores for about $16. They can be used on any two piece toilets. All types of float valves have installation instructions included in the package.

  • If a toilet with a flapper runs occasionally throughout the day, check if the chain or plastic strap that lifts the flapper is too tight. It must hang slightly loose. Next, inspect the flapper. If it is warped or it looks or feels worn, replace it. Most flappers can be replaced with a universal flapper, designed to fit a conventional 2” flush valve, but some late model 1.6 gal/flush toilets use a 3” flapper. Some toilets require that you use a flapper of that brand. Also, if your toilet uses 3.5 gal/flush or more you may prefer a flapper that is designed to use less water. See Appendix C, “How to Choose a Flapper”. Before putting on the new flapper, use a paper towel to clean rubber deposits off of the seat that the flapper rests on. If the flapper is not warped or worn the seat may be causing the leak. Run your finger around the seat; if you feel a rough spot, this may be causing the leak. Scour the seat with emery cloth or fine steel wool. Don’t use sandpaper because it could scratch the surface. A metal seat may have mineral deposits, which can be scraped off with a wood chisel.

If you don’t feel a rough spot, replace the flapper. Check if the tank still leaks by turning off the water at the toilet shut off valve, and checking if the tank is full hours later. If the tank still leaks, either the gasket at the base of the flush valve is worn, or the seat that the flapper rests on isn’t smooth enough. You could mount a new seat onto the original seat or you could replace the flush valve. Replacing the flush valve will replace the seat and also the gasket at the base of the flush valve. Flush valves designed for conventional toilets with 2” openings are available wherever toilet parts are sold. Instructions for installing them are included in the packages. A new seat can be mounted onto a metal or plastic seat. A kit for this, the “Fluidmaster™ Flusher Fixer Kit”, is sold wherever toilet parts are sold. It is a flush valve that is mounted to the seat with epoxy putty. There are some styles of seats that it cannot be mounted to; these are indicated on the package. Use a hair dryer to thoroughly dry the seat before applying the epoxy.

When you replace a flapper, it is better not to turn off the toilet shut off valve because this could cause it to leak onto the floor. If you turn off the valve and if it leaks when you turn it on, it may stop leaking if you fully open it, and it will always stop leaking if you tighten the packing nut. Use two pliers or wrenches to tighten it.

  • If a toilet with a tank ball runs occasionally throughout the day, first check if the “guide arm” should be adjusted. This guides the tank ball to the valve seat, and the ball must fall into the exact center of the hole. If you must adjust it, be careful not to break off the brass overflow tube; these become weak as they get old. Scour the seat with emery cloth or fine steel wool to make a water tight seal. If the surface is rough, use a coarser grade of steel wool. Don’t use sandpaper because it could scratch the surface. It may have mineral deposits on it, which can be scraped off with a wood chisel. Check if the tank leaks by turning off the water at the toilet shut off valve, and checking if the tank is full hours later. If the tank still leaks, replace the tank ball and the lift wires. The lower lift wire must be replaced because its threads may not be compatible with the threads on the new tank ball. If the tank still leaks, you could either replace the flush valve, or remove the guide arm, lift wires and tank ball and mount a new seat and flapper onto the old seat. A kit for this, the “Fluidmaster™ Flusher Fixer Kit”, is sold wherever toilet parts are sold. With this kit, a thin plastic seat is glued to the original seat with epoxy putty. If you mount a new seat and the toilet still leaks, the leak is caused by a worn gasket at the base of the flush valve. You must replace the flush valve or replace the gasket. A conventional 2” flush valve with a flapper can be used. You must remove the tank to install it. Instructions are given with the flush valve.

When you replace a tank ball, it is better not to turn off the toilet shut off valve because this could cause it to leak onto the floor. If you turn off the valve and if it leaks when you turn it on, it may stop leaking if you fully open it, and it will always stop leaking if you tighten the packing nut. Use two pliers or wrenches to tighten it.

  • If a toilet with a flush valve disk runs occasionally, first check if the seat that the disk or seat rests on feels smooth. If not, clean it with an abrasive pad, and check if the tank leaks. Check it by turning off the water at the toilet shut off valve, and checking if the tank is full hours later. If it still leaks, replace the flush valve disk. There are two types of flush valve disks: those that screw on, and those that pop on. If you try to pop off a screw-on disk you may break the flush valve, so if unsure which type it is, first try to screw it off. After replacing the flush valve disk, check if the tank leaks. If it still leaks, replace the flush valve with a similar flush valve. All of the flush valves of this style are American Standard brand, designed to be used in one-piece toilets. They are available in home centers and plumbing supply stores.

American Standard flush valve

  • If you have a Mansfield flush valve and the toilet runs occasionally, replace the flush valve seal. Mansfield flush valve seals are available at plumbing supply stores and some large hardware stores. If you replace the seal and the tank still leaks, replace the flush valve. A conventional 2” flush valve can be installed, but Mansfield flush valves use Mansfield flush valve handles so the handle must also be replaced. Flush valves for toilets with 2” openings are available wherever toilet parts are sold. Instructions for installing them are included in the packages.

Mansfield flush valve Mansfield flush valve seal

  • Check for small, unnoticeable leaks in the tank. Water can leak out of a tank unnoticed through several paths. When water leaves a tank through any type of leak, most goes down the drain but some enters the bowl, so if you add coloring to the water in the tank a leak will cause the water in the bowl to change color. You could pour food coloring, instant coffee, or powdered fruit drink mix into the tank until the water has a deep color. If you add coloring to the water in the tank and the water in the bowl changes color, shut off the water at the toilet shut off valve. If the water level in the tank has not fallen hours later, the fill valve is leaking through the refill tube into the overflow pipe. Replace the fill valve. If the water level in the tank has fallen, the leak is at the flush valve. Either the rubber gasket at the bottom of the flush valve is leaking or the flapper, tank ball, flush valve disk, or Mansfield flush valve seal is leaking. To repair it, see the measure above that explains how to repair or replace your type of flush valve. If you turned off the toilet shut off valve, check if it has begun to leak when you turn it back on. If it is leaking, tighten the packing nut.

Packing nut

Toilet shut off valve

  • If you have a pressure-assisted toilet that runs continuously or must be flushed more than once, you can probably repair it yourself. Most, if not all manufacturers of pressure-assisted toilets have a “trouble shooting guide” for their toilets on their company web sites, which give the possible causes of any problem. For detailed instructions on doing repairs, some books on plumbing for homeowners explain how to repair a pressure-assisted toilet.
  • If a toilet sometimes runs while the tank stays empty, until you jiggle the flush handle to make it stop, there are several possible causes. If the flush handle is metal and it is too tight, it may be corroded. Apply penetrating oil, or remove it and clean it with vinegar, or replace it. If the flush valve has lift wires and a tank ball, check if the “guide arm” should be adjusted. This guides the tank ball to the valve seat, and the ball must fall into the exact center of the hole. If you must adjust it, be careful not to break off the brass overflow tube. These become weak as they get old. If the lift wires are corroded, replace them or lubricate them. If the fill valve has a rod and float ball, check if the float ball rubs against the tank. If the toilet has a flapper with a lift chain, the lift chain may be too long, and occasionally get tangled. If the flush handle is loose and the toilet has a flapper, the flapper may not always fall onto the center of the flush valve seat. Tighten the flush handle retaining nut.
  • If you have a toilet that flushes with 3.5 gallons or more, replace the flapper with a water saving flapper. They should be installed in 5.5 gal/flush toilets, but not in 1.6 gal/flush toilets. In 3.5 gal/flush toilets, it is arbitrary- they reduce the use of water but slightly decrease the effectiveness of the toilet. There are at least three types. Your local store may have only one type, but whichever you buy will be effective. They all reduce the water used by closing the flush valve before all the water has drained out. These three types of flappers are described in Appendix C, “How to Choose a Flapper.”

Adjust-A-Flushflapper Time rated flapper Flapper with float

  • If a toilet has a water saving flapper, adjust it to use less water and check if the toilet still flushes well. The three common types of water saving flappers are the “Adjust-A- Flush™, the “time rated flappers” and flappers with floats. These are pictured above. If your toilet has a Fluidmaster™ Flusher Fixer™, this can also be adjusted to use less water. As explained in Appendix C, AdjustA-Flush™ flappers are adjusted by rotating the rubber piece, time rated flappers are adjusted by replacing the plastic nozzle, and flappers with floats are

Fluidmaster Flusher Fixer

adjusted by sliding the float up or down the chain or strap. You adjust a Fluidmaster™ Flusher Fixer™ by adding or removing tiny plastic plugs that are in four drain holes in the bottom of its timing cup. The number of drain holes that are plugged determines how fast the flapper closes and how much water is used. To add a plug you clip it off from under the timing cup and push it into one of the holes.

  • If a toilet occasionally must be flushed more than once, there are several possible causes.
    1. The water level in the tank may be set too low. It should be about ½” below the top of the overflow tube. If it is a float cup fill valve, raise the water level by releasing the spring clip or turning the large plastic screw, depending on the model, to raise the float cup. If you can’t raise it any higher, raise the upper part of the fill valve by rotating it by 2 or 3 rotations.

Rotate valve shank to raise the Release the spring clip to raise float ball

water level in the tank

If it is a cartridge (floatless) ballcock, raise the water level by turning the adjustment screw.

Turn the adjustment screw on a

floatless ballcock

If the fill valve has a brass rod and a floating ball, bend the brass rod upward.

If the fill valve has a plastic rod and a floating ball, turn the adjustment screw.

    1. If the toilet has a water saving flapper, adjusting the flapper to increase the water per flush could solve the problem. See Appendix C,”How to Choose a Flapper”. If the toilet has a Fluidmaster™ Flusher Fixer™, clip off a plug from under the “timing cup” and push it into one of the holes in the bottom of the cup. The number of drain holes that are plugged determines how fast the flapper closes and how much water is used when the toilet is flushed.

Fluidmaster Flusher Fixer

    1. The vent stack could be clogged. This is the large pipe that leads from the toilet drain to the roof, and sticks out of the roof. Air must enter through this pipe for the toilet to flush well. It can be clogged by a bird’s nest or a small animal. To check for a clogged vent stack, run a snake through it from the roof. Snakes can be rented at rental centers.
    2. The toilet could be partially clogged by an obstruction. A comb or toy could be stuck in the toilet’s trap (trapway). A toilet plunger may open the obstruction, but if an object is tightly jammed you will need to use a toilet snake (closet auger) to remove it. These are sold at home centers.
    3. In very old toilets, mineral deposits could be partially blocking the toilet’s trap (trapway). To check for this you must remove the toilet, reach into the trap and feel the surface. You may not be able to repair this problem.
    4. The first 1.6 gal/flush toilets, which were sold in 1994 and for a few years after, flushed poorly. Some homeowners replaced them because they often had to be flushed twice.
    5. The drain below the toilet could be partially clogged. To repair this you must remove the toilet and snake the drain with a large electric snake.
  • Replace the fill valves with fill valves that are designed to warn you when water is leaking from the tank. They don’t open to let the tank fill when the tank water level becomes low unless you have just flushed the toilet. Different brands are sold in some hardware stores for about $16. They can be used on any two piece toilet.
  • If you have old, metal flush valve seats, scour them with fine steel wool. This will prevent leaking, which is likely to happen sooner or later. Do not use sandpaper because it could scratch the surface.
  • Check if any of your toilets are supplied with hot water, by checking if their supply lines feel warm. In hot, humid climates, some plumbers install hot water piping to the toilets to prevent the condensation that is formed on the tanks, which drips onto the floor. If a toilet is supplied with hot water, hire a plumber to replace the hot water piping with cold water piping. To prevent condensation, buy a toilet insulation kit. The kit includes a thin sheet of foam, and adhesive to glue the sheet to the tank’s inside, back wall. If you live in a hot, humid climate they are available in some hardware stores.

Appendix A Selecting a Toilet

There are two basic categories of toilets; gravity-flow and pressure-assisted. Gravity-flow toilets are conventional toilets; they have an elevated tank that the water drains from to flush the toilet. Pressure-assisted toilets use the home’s water pressure to create pressure in a large tank hidden in a conventional tank. This pressure is used to flush the toilet. They are not electric. Most, if not all major manufacturers offer a pressure-assisted toilet. Dual-flush gravity-flow toilets have two buttons in place of a flush handle. You can press one button to flush with 1.6 gallons or the other button to flush with less; usually .8 or 1.0 gallons. Conventional gravity-flow toilets range in price from under $100 to well over $1000. At the bottom of the price range, the toilets are noisier when flushed, less attractive, and occasionally must be flushed more than once. Pressure-assisted toilets range in price from about $500 to well over $1000. Dual-flush gravity-flow toilets start in price at about $200.

Replacing a toilet gives you the opportunity to choose from many different styles, sizes, colors and features. Heights range from 12” to 20”; older people often prefer an 18” high toilet to the conventional 14” high toilet. Toilets with accessories for the handicapped are available. Manufacturers now offer toilets in up to 16 colors. The web site of any major home center or major toilet manufacturer will display hundreds of toilets to choose from.

Almost all pressure-assisted toilets have flush rates of either 1.6 or near 1.0 gal/flush. They have more flushing power than gravity-flow toilets, so a 1.0 gal/flush model may be an acceptable substitute for a 1.6 gal/min gravity-flow toilet. If your toilet clogs frequently or your plumbing system is over 50 years old, a 1.6 gal/flush pressure-assisted toilet may be your best choice because it will seldom if ever clog. Also, they have no tank sweat from condensation in hot, humid weather. The most common complaints people have about them are that they are too noisy and they are harder to repair. Not all models are noisy, and they aren’t actually hard to repair; homeowners who know how to repair conventional toilets can get frustrated when they have to re-train themselves in toilet repair. Also, the parts often must be ordered.

Gravity-flow toilets have either 3” or conventional 2” flush valves. Those with 3” flush valves have more flushing power because the water drains more rapidly. They have flappers that appear very large. Toilets labeled as “high efficiency” have flush rates of less than 1.6 gal/flush, normally 1.28 gal/flush, the maximum to qualify as high efficiency. There are many of these toilets in the price range of $200 to $300. Toilets labeled as “high performance” have a relatively forceful flush. Most of these have 3” flush valves.

 

Appendix B How to Install a Toilet

To install a toilet, follow the instructions included with the toilet. They will explain how to remove your old toilet, how to mount the toilet bowl to the floor, how to mount the tank to the bowl and how to install the parts in the tank. Either buy a toilet seat or use the old one. You may need to replace the supply tube if the one you have is copper tubing and it can’t be reused. Replace it with a flexible toilet supply tube; these are easy to connect (plumbers use copper tubing supply pipes because they cost less). To buy a supply tube you only need to choose the length. All of the toilet supply tubes in the local hardware store or home center will have the standard 7/8” fill valve connection at one end and the standard 3/8” compression connection at the other end. A 12” supply tube can probably be used for any toilet, but it is longer than necessary for some toilets. Whether you replace the supply tube or re-use the old one you should wrap the threads with Teflon™ tape.

Buy a wax toilet bowl gasket. Solid wax gaskets without the plastic cones can be used with any toilet. The hole in the bottom of a toilet is 4” and the flange is 4”. The elbow below the flange is either 3” or 4” diameter (3” or 4” waste line). If you buy a wax gasket with a plastic cone (“no-seep” wax ring) and you have a 3” waste line it must say on the package, “fits 3” and 4” waste lines”. No-seep wax rings are very popular because they make it easier to set the toilet in the correct spot. If you are inexperienced at mounting a toilet, buy at least two gaskets because if you don’t set the toilet in the right spot you must re-set it using a new gasket. Also, if the toilet rests on thick tile you may need to use two gaskets.

When you remove the toilet you may find that the flange it was bolted to is broken. Both old cast iron flanges and newer plastic flanges often break. Home centers, hardware stores and plumbing supply stores sell two types of toilet repair flanges that can be used in place of replacing a broken flange. One type is only a few inches long. You place it under the broken area of the old plastic or metal flange, in a position where it holds the flange bolt (floor bolt) in the correct place. The other type is the same size as the toilet flange. You open it, and close it to mount it behind the old flange. It supports the flange bolts. For extra strength, screw it into the floor where possible. If the floor is concrete, use self-tapping masonry screws.

Wax toilet bowl gasket Two types of toilet repair flanges

You should replace the flange bolts, because normally, after the toilet was mounted the old bolts were cut to the minimum length, or if they are “snap-off toilet bolts” the top ½” was broken off. The old bolts are probably too short to hold with the pliers as you turn the nut.

As explained in the toilet’s instructions, place the wax ring on the toilet and mount the toilet over the bolts. Sit on the toilet to set the wax gasket, and then bolt down the toilet. Do not over tighten the bolts. This could crack the bowl. Do not cut the flange bolts until you have finished installing the toilet and flushed it several times to check for leaks. If the toilet leaks you must re-mount it using a new wax gasket.

3½” Snap-Off Flange bolts 12”flexible toilet supply tube

Appendix C How to Choose a Flapper

If the flapper you are replacing appears to be much larger than a conventional flapper, the toilet has a 3” drain instead of a conventional 2” drain. You must buy a “large flapper”. They are available wherever toilet parts are sold. If your toilet has a conventional 2” drain, a universal flapper can probably be used, but many expensive toilets require a flapper of that brand. Some models of Kohler toilets and Gerber toilets, for example, require Kohler and Gerber flappers. These are both sold in home centers but others are not. Plumbing supply stores

have a better selection of flappers than hardware stores or home centers. Most stores sell at least one brand that is designed to last longer. “Guaranteed to last 5 years” is usually written on the package. If you use chlorine toilet tank treatments or if chlorine is put in your water, it would be good to buy a flapper designed to resist chlorine. These may

be called “premium flappers” and will Universal flapper

have written on the label, “designed to withstand chlorine”, or “silicone treated to resist chemicals”. If the flapper you are replacing wore out too soon and you used toilet bowl cleaner in the toilet, this was probably the reason. Buy a flapper labeled, “designed to resist harsh chemicals”.

If your toilet uses more than 1.6 gal/flush (it was installed before 1994), you may choose to replace your flapper with a water saving flapper. They should be installed in all 5.5 gal/flush toilets, but in 3.5 gal/flush toilets, it is arbitrary- they reduce the use of water but slightly decrease the effectiveness of the toilet. That is, at times you may have to flush twice. This is only a potential problem in homes with relatively poor drainage; mainly very old homes. Water saving flappers are designed to close before all of the water has drained from the tank. The water at the bottom of the tank is saved, and this water adds very little to the forcefulness of a flush. The toilet will flush better than if you were saving the same amount of water by using an old-fashioned “toilet dam”, which blocks off the water in a section of the tank. Water saving flappers are adjustable, but you can’t set them to use 1.6 gal/flush in a 3.5 gal/flush toilet because the toilet would not flush well enough.

There are at least three types of water saving flappers. One type has a float on the pull chain or plastic strap. It holds the flapper up as the tank drains. If the distance from the flapper to the float is, for example, 2”, when the water level falls to 2” above the flush valve seat the flapper closes. You can slide the float higher or lower to increase or decrease the amount of water that is used with each flush, so if it flushes poorly you can lower the float. The other two types of adjustable flappers, the Adjust-A-Flush™, and time-rated flappers work on the same principle. When the flapper is lifted it becomes filled with water, which enters through a hole in the side. When the water level falls to the level of the flapper the water in the flapper begins to drain out of it through a hole in the bottom. When enough water has drained out the flapper falls, closing the flush valve. On both types of flappers, you adjust the rate that the water drains out of the flapper to control how fast it falls, and how much water drains from the tank when the toilet is flushed. You adjust an Adjust-A-Flush™ flapper by rotating the rubber part, and you adjust a time-rated flapper by changing a nozzle (baffle) at the bottom, which the water drains out of. Five nozzles with different sized openings are in the package.

High dome style flapper for Flapper for Kohler toilets

Gerber toilets

3” flapper for Toto Power Gravity toilet

Adjust-A-Flushflapper Time rated flapper Flapper with float