One of the most useful design elements for environmental bathrooms is a dual-flush system. Dual-flush tanks offer two choices: a low-volume flush (usually 0.8–1.1 gallons) for liquid waste and a higher volume flush (approximately 1.28–1.6 gallons) for solids. https://tannda.net/read-blog/202359_how-to-choose-the-right-flush-tank-for-your-bathroom-a-comprehensive-guide.html