Code Stories · why the rule exists

Maximum Flush Volume: 1.6 gpf and the Energy Policy Act of 1992

The rule in Massachusetts today

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))

248 CMR 10.10(2)(f) (toilets); 10.10(3)(c) (urinals); 10.10(4)(c)3 (showerheads); 10.10(10)(a)2-3 (public lavatory faucets) · confirm in the current 248 CMR

Why it exists

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.

How it came to be

1988 — Massachusetts adopts a phased-in 1.6-gallon requirement. csmonitor.com
1970s-1990 — Why early low-flow toilets were bad: manufacturers put smaller tanks on bowls designed for more water. csmonitor.com
1992 — Energy Policy Act of 1992 enacted (Public Law 102-486). govinfo.gov
1992 — EPAct's water closet standard as codified at 42 U.S.C. 6295(k). law.cornell.edu
1994-1997 — 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. law.cornell.edu
2012 — Alliance for Water Efficiency on the size of the cut. allianceforwaterefficiency.org

Make it stick

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).

On the exam

Expect MA maximums: toilets 1.6 gpf (6.0 L), urinals 1.0 gpf (3.8 L), showerheads 2.0 gpm (MA; the federal figure is 2.5 gpm at 80 psi, so do not use it on the MA exam), public and employee lavatory faucets 0.5 gpm, metering faucets 0.25 gal per cycle. Also know that the limits apply to new fixtures, not to toilets already installed.

What people get wrong

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.

Try it: 1 real practice question

Q1. The maximum flush volume for a new water closet is:

These come from the PressureTest bank. Start 7 days free for the full bank, timed exam simulations and drawn isometric problems.

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Sources

History is presented as history. The current Massachusetts rule is the box at the top — use it on the exam.