MIL-HDBK-1165
5.2.1
Toilets
5.2.1.1
Conventional and Water-Efficient. Toilets account for
approximately 45 percent of indoor water use (Figure 4), making
them a prime candidate for water conservation measures. The most
common types of toilets are the gravity flow toilet, flush valve
toilet, and pressurized tank system.
a) Gravity toilets. Gravity toilets work by using a
tank of water and a rubber stopper. The water is released by the
stopper and enters or "flushes" into the bowl from the tank by
gravitational force.
b) Flush valve toilets. Flush valve toilets have no
tanks. Instead, pressurized water pipes are activated by valves
to release water at specific flow rates into the bowl.
Typically, gravity flow toilets are seen in residential
buildings, and flush valve toilets in office and administration
buildings.
c) Pressurized tank toilets. Pressurized tank toilets
are a newer design of the old tank toilet and are made to use 1.6
gpf (6.0 lpf) or less. Here, an air bag in the tank exerts
pressure on the water to force it down into the bowl. "Blowdown"
toilets are pressurized tank toilets with the tank hidden behind
the wall.
d) Traditional toilets. Traditional toilets
(manufactured before 1980) are primarily gravity flow or flush
valve and use 5 to 7 gpf (19 to 26.5 lpf). Since 1980, low flow
toilets using 3.5 gpf (13 lpf) and ultra low flow (ULF) toilets
using 1.6 gpf (6 lpf) have been introduced into the marketplace.
Unless your facilities have been renovated or newly built since
1980, it is likely that you are currently using high-flow
toilets, and wasting significant amounts of water. Replacing a
conventional toilet with a 1.6 gpf (6 lpf) toilet can reduce
toilet water usage by as much as 70 percent per day! Although
not as effective as replacing a conventional toilet with an ULF,
operation and maintenance procedures and retrofitting can reduce
the amount of water your existing toilets use and make them more
efficient. However, some retrofits may require frequent
adjustment or maintenance and may interfere with the proper
operation of the toilet, which was not designed to work with low
volumes of water.
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