It’s an old water-saving trick, and it’s making the rounds again: a Czech news site reported last week that a single plastic bottle in the toilet tank can cut the water bill, adding that most people put it in wrong. Here’s what the bottle is for, how much it really saves, and the toilets where it’s not worth doing.
In short
- A closed plastic bottle filled with water or pebbles goes in the toilet tank, away from the flush mechanism.
- It takes up space, so the tank refills with less water at every flush.
- In an older toilet, that can save up to 1 gallon per flush, according to University of Nebraska-Lincoln Extension.
- Never use a brick, and on a newer low-flow toilet, there’s little to gain.
What the bottle is for
Toilets account for “nearly 30 percent of an average home’s indoor water consumption,” according to the EPA’s WaterSense program, and older, inefficient models use “as much as 6 gallons per flush.” A bottle in the tank simply takes the place of some of that water. The tank fills to the same level, but it holds less, so each flush uses less.
The Czech site Centrum.cz describes a PET bottle filled with sand, and warns that most people put it in wrong. University of Nebraska-Lincoln Extension gives the same advice: “A container can typically result in a savings of up to 1 gallon of water per flush.”
How to do it
- Use a plastic container, such as a small bottle or a milk jug, and fill it with water or pebbles so it doesn’t float. Close it tightly.
- Lift the tank lid and find the moving parts: the flapper at the bottom, the fill valve and the float.
- Set the bottle where it won’t touch them. UNL’s rule is to “avoid interfering with the flushing mechanisms or the flow of water.”
- Flush and watch. The flapper must close freely and the float must move without hitting the bottle.
Check what kind of toilet you have first
The trick was made for older toilets. The federal standard today is 1.6 gallons per flush, and WaterSense models use 1.28 gallons or less, the EPA says. In those toilets, there’s little water left to spare. Even in older models, UNL notes that “about 3 gallons of water per flush should be maintained for adequate flushing.” If you find yourself flushing twice, the bottle is costing you water, not saving it: take it out.
The limit
Never use a brick: UNL warns against “bricks or other objects that can release particles of soil, stone, or corrosive materials into the tank.” A bottle is a small fix on an old toilet. The real savings come from replacing it: the EPA says WaterSense toilets can save a family nearly 13,000 gallons and more than $170 a year in water costs.
While the lid is off, the rest of the bathroom deserves a look too: here’s what’s replacing the toilet brush, why people are spraying vinegar around the toilet, and the best way to remove limescale from the toilet.
One bottle, the right spot and a test flush. That’s the trick.
