19
MIXING VALVES
Water temperature over 125°F (52°C)
can cause severe burns instantly
resulting in severe injury or death.
Children, the elderly and the
physically or mentally disabled are at
highest risk for scald injury.
Feel water before bathing or
showering.
Temperature limiting devices such as
mixing valves must be installed
when required by codes and to
ensure safe temperatures at fixtures.
Water heated to a tempe rature which will sati sfy clothes washing,
dish wa shing, and other sanitizing needs can scald and cause
permanent injury upon contac t. Short repeated heating cycles
caused by small hot water uses can cause temperatures at t he
point of use to exce ed the wate r heater’s tem perature setting by
up to 20°F (11°C).
Some people are more likely to be permanently injured by hot water
than others. These incl ude the elderly, children, the in rm and the
physically/mentally disabled. Table 4 shows the approximate time-
to-burn relationship for normal adult skin. If anyone using hot water
provided by the water heater being installed ts into one of the se
groups or if there is a loc al code or state law requiring a certain
water temper ature at the point of use, then s pecial prec autions
must be taken.
In addition to u sing the lowest poss ible temperature setting that
satises the demand of th e application a Mixing Valve should be
installed at the water heater or at the hot water taps to further
reduce system water temperature.
Mixing valves are availab le at plumbing supply stores. Consult
a Qualied Installer or Servic e Agency. Follow mixing valve
manufacturer’s instructions fo r installation of the valves.
In all cases, the following burn ta ble must be used.

Table 4

Water Temperature
°F (°C)
Time for 1st Degree Burn
(Less Severe Burns)
Time for Permanent
Burns
2nd & 3rd Degree
(Most Severe Burns)
110 (43.3) (normal shower temp.)
116 (46.7) (pain threshold)
116 (46.7) 35 minutes 45 minutes
122 (50) 1 minute 5 minutes
131 (55) 5 seconds 25 seconds
140 (60) 2 seconds 5 seconds
149 (65) 1 second 2 seconds
154 (67.8) instantaneous 1 second
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)
GAS PIPING
Make sure gas supplied is same type listed on model rating plate. The
inlet gas pressure must not exceed 14 inch water column (3.5 kPa) for
natural and propane gas (L.P.). The minimum inlet gas pressure shown
on rating plate is that which will permit ring at rated input.
SEDIMENT TRAPS
A sediment trap shall be installed as close to the gas inlet of the
water heater as practical at the time of water heater installation. The
sediment trap shall be either a tee tting with a capped nipple in the
bottom outlet or other device recognized as an effective sediment
trap.
Contaminants in the gas lines may cause improper operation of the
gas control valve that may result in re or explosion. Before attaching
the gas line be sure that all gas pipe is clean on the inside. To trap
any dirt or foreign material in the gas supply line, a sediment trap
must be incorporated in the piping. The sediment trap must be readily
accessible. Install in accordance with the Gas Piping section. Refer
to the current edition of the National Fuel Gas Code (ANSI Z223.1/
NFPA 54).
Use pipe joint compound or teon tape marked as being resistant to
the action of petroleum [Propane (L.P.)] gases.
The water heater and its gas connection must be leak tested before
placing the water heater in operation.
The water heater and its individual Shut-off valve shall be disconnected
from the gas supply piping system during any pressure testing of that
system at test pressures in excess of 1/2 pound per square inch (3.5
kPa). It shall be isolated from the gas supply piping system by closing
its individual manual Shut-off valve during any pressure testing of the
gas supply piping system at test pressures equal to or less than 1/2
pound per square inch (3.5 kPa).