Code Stories · PressureTest
Verbatim: 10.10(2)(f) "Toilets shall use a maximum of 1.6 gallons (6.0 liters) per flush." 10.10(3)(c) "Urinals shall use a maximum of one gallon (3.8 liters) per flush." 10.10(4)(c)3 "Shower heads shall use a maximum of 2.0 gallons per minute (G.P.M.)." 10.10(10)(a)2 "The maximum flow rate for faucets shall not exceed 0.5 gallons per minute (G.P.M.)".
New water closets: maximum 1.6 gallons (6.0 liters) per flush (248 CMR 10.10(2)(f))
Toilets are one of the largest indoor water uses, and every gallon flushed also has to be pumped, treated and carried by the sewer. Cutting flush volume saves both supply and wastewater capacity at the same time.
The federal law set a uniform national ceiling so manufacturers had to redesign bowls and trapways around less water. Swapping a smaller tank onto an old bowl was the shortcut that gave early low-flow toilets a bad name.
Massachusetts adopts a phased-in 1.6-gallon requirement.
Source: https://www.csmonitor.com/1990/0620/dplumb.html
Why early low-flow toilets were bad: manufacturers put smaller tanks on bowls designed for more water.
Source: https://www.csmonitor.com/1990/0620/dplumb.html
Energy Policy Act of 1992 enacted (Public Law 102-486).
Source: https://www.govinfo.gov/content/pkg/STATUTE-106/pdf/STATUTE-106-Pg2776.pdf
EPAct's water closet standard as codified at 42 U.S.C. 6295(k).
Source: https://www.law.cornell.edu/uscode/text/42/6295
Transitional exceptions: 'Commercial Use Only' 2-piece gravity toilets at 3.5 gpf until 1997; flushometer-valve toilets 1.6 gpf after Jan 1, 1997; urinals 1.0 gpf.
Source: https://www.law.cornell.edu/uscode/text/42/6295
Alliance for Water Efficiency on the size of the cut.
Source: https://allianceforwaterefficiency.org/20-years-energy-policy-act-18-trillion-gallons-saved-through-more-efficient-toilets/
Mnemonic: 'Mass. went first in '88; the feds followed in '92.' And a true image for why the first low-flows clogged: a Volkswagen engine in an Oldsmobile (CSM, 1990).
The federal law made people rip out old toilets.
The standard applies to products manufactured after the effective dates. It is not a retrofit mandate.
1.6 gpf was a federal idea.
Massachusetts passed a 1988 law phasing in the 1.6-gallon standard (CSM 1990), four years before EPAct 1992 made it national.
Low-flow toilets can't work.
Early failures came from putting small tanks on old bowl designs (CSM). Redesigned bowls and trapways solved that.
The maximum flush volume for a new water closet is:
248 CMR 10.10(2)(f) caps new water closets at a maximum of 1.6 gallons (6.0 liters) per flush. Lower-flow models are allowed, but 1.6 gpf is the code maximum the exam tests.
pressuretest.me/learn/max-flush-volume-1-6-gpf/