Pre-1994 toilets: 3.5–7 gallons per flush (gpf) - Standard modern toilet (post-1994): 1.6 gpf - High-efficiency toilet (HET): 1.28 gpf - Dual-flush toilet: 0.8–1.6 gpf depending on mode - Running toilet: 20–50 gallons per hour wasted - Annual cost of a running toilet: $30–$70/month or $360–$840/year