What should I look for when buying flush performance & water efficiency?

MaP 800g+ is the most important spec. WaterSense at 1.28 GPF saves thousands of gallons per year. TOTO Drake is the benchmark: 800-1000g MaP at 1.28 GPF.

What are common mistakes when buying flush performance & water efficiency?

Choosing 1.0 GPF without checking MaP -- may need double-flushing. Ignoring MaP entirely. Assuming WaterSense means weak flush.

Flush Performance & Water Efficiency

Buying Guide

Created by Ryan Pietrzak Illinois Licensed Plumber · In the plumbing industry since 2009

Updated February 20, 2026

Key Takeaway

A toilet that saves water but needs two flushes wastes more. MaP testing provides objective flush performance data. WaterSense ensures efficiency. The best toilets score high on both.

Overview

A toilet that saves water but needs two flushes wastes more. MaP testing provides objective flush performance data. WaterSense ensures efficiency. The best toilets score high on both.

What to Know

MaP Scores

Measures grams cleared in one flush. 250g minimum. 500g good. 800g+ excellent. Look for 800+ for reliable single-flush performance.

GPF Ratings

Federal max 1.6 GPF. WaterSense: 1.28 GPF or less. High-efficiency: 1.0-1.1 GPF. Lower GPF only matters if the flush actually clears waste.

WaterSense

EPA program: 1.28 GPF or less AND passes flush testing. Saves 20% water. Many utilities offer $50-100 rebates.

Buying Tips

MaP 800g+ is the most important spec.
WaterSense at 1.28 GPF saves thousands of gallons per year.
TOTO Drake is the benchmark: 800-1000g MaP at 1.28 GPF.
Check for utility rebates on WaterSense toilets.

Common Mistakes

Choosing 1.0 GPF without checking MaP -- may need double-flushing.
Ignoring MaP entirely.
Assuming WaterSense means weak flush.
Buying based on GPF alone.

Bottom Line

WaterSense certified (1.28 GPF) with MaP 800g+. Saves water AND flushes well.