4.10 Water connections
▶ This heater is not approved for preheated water
applications exceeding 140°F (60°C).
▶ In applications where inlet water temperature can exceed
140°F (60ºC), a 3-way valve or mixing valve must be
installed before the appliance to prevent water exceeding
140°F (60°C) from entering the appliance.
▶ When facing the heater, the ¾" cold connection is on the
bottom right and the hot connection is on the bottom left.
Centrally locating the water heater is recommended to
keep hot water distribution times even throughout the
 Hot connection
 Cold connection
 Water filter
▶ The use of unions when connecting both water pipes to the
inlet and outlet connections is required. This will facilitate
any necessary servicing.
▶ Plastic or PEX type plumbing line materials are not suitable
for connecting directly to the water heater.
▶ Although water piping throughout the building may be
other than copper, we recommend that copper or suitably
rated stainless steel flex line piping be used for the water
connections for 1.5' on either side of the water heater
(follow local codes if more stringent).
▶ Never sweat any piping directly to or beneath the water
connections, as damage will occur to the internal water
valve from heating of the pipe.
▶ Keep water inlet and outlet pipes to no less than ¾"
(19.05mm) diameter to allow the full flow capacity.
▶ If the cold and hot connections to the heater are reversed,
the heater will not function. Be certain there are no loose
particles or dirt in the piping. Blow out or flush the lines
before connecting to the water heater.
▶ Full port shutoff valves should be installed on both the cold
water supply and hot water outlet lines to facilitate
servicing the heater (see fig. 34).
▶ For installation on a private well system with the use of a
pressure tank, the lowest pressure range setting
recommended is 40-60 psi (2.75 - 4.15bar).
4.11 Water quality
Water quality can have an impact on appliance longevity and
may void the manufacturer's warranty.
For water analysis data call your local water department, or if on
a well, have well water analyzed periodically. If water quality
exceeds one or more of the values specified below, Bosch
940 ES – 6 720 644 930 (2019/09)