The capacity of a flush tank refers to the amount of water it can hold and release during a flush. This capacity varies depending on the type, age, and design of the toilet. In recent years, there has been a significant focus on water conservation, leading to the implementation of standards and the development of more water-efficient toilets.
Key Facts
- Federal standards in the U.S. and Canada mandate that the “full” flush volume of a toilet cannot exceed 1.6 gallons (6.0 liters), and the “reduced” flush volume cannot exceed 1.1 gallons (4.2 liters).
- In the early 90s, the U.S. government mandated a standard toilet tank size, limiting it to six gallons per flush (gpf).
- Before 1982, toilets in the United States could use as much as 5 to 7 gallons of water per flush.
- From 1982 to 1993, many toilets were made to use 3.5 gallons per flush.
- Newer toilets, designed to be more water-efficient, use 1.6 gallons or less per flush.
- Some water-efficient toilets can use even less than 1.6 gallons, with 1.28 gallons or less per flush.
Historical Perspective
Prior to the 1980s, toilets commonly used 5 gallons (19 liters) or more per flush. In the 1980s, many codes and standards set the maximum flush volume at 3.5 gallons (13.25 liters), referred to as “water savers.”
Current Standards
In the United States and Canada, federal standards mandate that the “full” flush volume of a toilet cannot exceed 1.6 gallons (6.0 liters), and the “reduced” flush volume cannot exceed 1.1 gallons (4.2 liters). This regulation aims to conserve water and promote the use of more efficient toilets.
High-Efficiency Toilets (HET)
Beginning in the late 1990s, manufacturers introduced high-efficiency toilets (HET), defined as having an effective flush volume of 1.28 gallons/4.8 liters or less. HETs include both single-flush and dual-flush fixtures.
Single-Flush Toilets
Single-flush toilets have a single flush volume option, ranging from as little as 0.8 gallons (3.0 liters) to as much as 1.6 gallons (6.0 liters). Models certified to WaterSense flush with no more than 1.28 gallons (4.8 liters).
Dual-Flush Toilets
Dual-flush HETs allow the user to select a “full” flush to remove solids or a “reduced” flush to remove liquids only. The “full” flush volume cannot exceed 1.6 gallons (6.0 liters), and the “reduced” flush volume cannot exceed 1.1 gallons (4.2 liters).
Conclusion
The capacity of a flush tank has undergone significant changes over time, with a focus on water conservation and efficiency. Current standards and the development of HETs have led to a reduction in the amount of water used per flush, contributing to more sustainable water usage in residential and commercial settings.
References
- MaP Testing: Toilet Types
- eHow: Standard Toilet Tank Size
- Hunker: How Much Water Is Supposed to Be in a Toilet Tank?
FAQs
What is the standard flush tank capacity in the United States and Canada?
The standard flush tank capacity in the United States and Canada is 1.6 gallons (6.0 liters) for a full flush and 1.1 gallons (4.2 liters) for a reduced flush.
How much water did toilets use before the 1980s?
Prior to the 1980s, toilets commonly used 5 gallons (19 liters) or more per flush.
What are high-efficiency toilets (HET)?
High-efficiency toilets (HET) are toilets that have an effective flush volume of 1.28 gallons/4.8 liters or less.
What is the difference between single-flush and dual-flush toilets?
Single-flush toilets have a single flush volume option, while dual-flush toilets allow the user to select a “full” flush or a “reduced” flush.
What is the maximum flush volume for a single-flush toilet certified to WaterSense?
The maximum flush volume for a single-flush toilet certified to WaterSense is 1.28 gallons (4.8 liters).
What is the maximum “full” flush volume for a dual-flush HET?
The maximum “full” flush volume for a dual-flush HET is 1.6 gallons (6.0 liters).
What is the maximum “reduced” flush volume for a dual-flush HET?
The maximum “reduced” flush volume for a dual-flush HET is 1.1 gallons (4.2 liters).
Why is there a focus on water conservation in toilet design?
There is a focus on water conservation in toilet design to reduce water usage and promote sustainability.