The Type of Bathroom Stool Tank That Has a Round Hole for the Flush Handle

Flush Toilets

• Early American flush toilets used as much as 7 gallons of water per flush, according to the University of Arizona Water Resources Research Center. Modern flush toilets work on the same general principles. Water in the bowl normally stays at a level below the top of the drain's siphon bend. Water flowing out of the tank during flushing raises the level in the bowl, pushing water over the top of the bend to start a powerful siphoning action. Remaining tank water completes the flush and the system resets. Modern gravity-flow toilets might need as little as 1.6 gallons per flush, and pressure-assisted toilets need even less.

Tank Designs

• Both the tank shape and volume changed as toilet designs met increasingly stringent standards of water consumption. Some manufacturers kept the external tank design the same and adapted the internal system to decrease water consumption. Other companies reduced the size of the tank. The highest level of water in the tank determines the head pressure, or the force used to start the flushing action. In some large tanks, an internal barrier prevents the last water from escaping, conserving water without lowering head pressure. Smaller tanks begin with less water volume, but similar head pressure, using nearly all the tank's contents on each flush.

Pressure-Assisted Toilets

• To save even more water, pressure-assisted toilets increase the velocity of water during the flush and extend the flush duration to about 10 seconds. Water system pressure adds to head pressure from the tank, pushing water and waste through the drain quickly. This special design reduces the size of the tank and requires a different type of connection to the home's water supply. Bowl design also changes, sometimes placing the toilet seat closer to the standing water level in the bowl. Pressure-assisted toilets use the same type of triggering as manually flushed standard and low-flush toilets.

Problems

• Where different types of tanks can physically fit to one type of toilet bowl, mistakes in tank choices can lead to failed flushes, overflows and increased water consumption. Finding the correct replacement tank depends on identifying the make and model of the bowl. Tanks with different decorative designs might fit the same toilet bowl and function properly, but low-flush or dual-flush tanks might not supply enough water to clear a bowl designed for a standard toilet tank. Replacing an old toilet completely provides many new choices, and a water-conserving toilet that functions properly can save money in the long run.