lp-181 Rev. 3.3.15
6
To avoid water damage or scalding due to relief valve operation:
• Discharge line must be connected to relief valve outlet
and run to a safe place of disposal. Terminate the
discharge line in a manner that will prevent possibility of
severe burns or property damage should the relief valve
discharge.
• Discharge line must be as short as possible and the same
size as the valve discharge connection throughout its
entire length.
• Discharge line must pitch downward from the valve
and terminate at least 6” above the floor drain, making
discharge clearly visible.
• The discharge line shall terminate plain, not threaded,
with a material serviceable for temperatures of 375
o
F or
greater.
• Do not pipe discharge to any location where freezing
could occur.
• No valve may be installed between the relief valve and
heater or in the discharge line. Do not plug or place any
obstruction in the discharge line.
• Test the operation of the relief valve after filling and
pressurizing the system by lifting the lever. Make sure
the valve discharges freely. If the valve fails to operate
correctly, immediately replace with a new properly rated
relief valve.
• Test T&P valve at least once annually to ensure the
waterway is clear. If valve does not operate, turn the
heater “off” and call a plumber immediately.
• Take care whenever operating relief valve to avoid
scalding injury or property damage.
FAILURE TO COMPLY WITH THE ABOVE GUIDELINES
COULD RESULT IN FAILURE OF RELIEF VALVE OPERATION,
RESULTING IN POSSIBILITY OF SUBSTANTIAL PROPERTY
DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
Do not thread a cap or plug into the relief valve or relief valve
line under any circumstances! Explosion and property damage,
serious injury, or death may result.
RE-INSPECTION OF T&P RELIEF VALVES: T&P valves should
be inspected AT LEAST ONCE EVERY THREE YEARS, and
replaced if necessary,
by a licensed plumbing contractor or
qualified service technician to ensure that the product has not
been affected by corrosive water conditions and to ensure that
the valve and discharge line have not been altered or tampered
with illegally. Certain naturally occuring conditions may corrode
the valve and its components over time, rendering the valve
inoperative. Such conditions can only be detected if the valve
and its components are physically removed and inspected.
Do not attempt to conduct an inspection on your own.
Contact your plumbing contractor for a re-inspection to assure
continued safety.
FAILURE TO RE-INSPECT THE T&P VALVE AS DIRECTED
COULD RESULT IN UNSAFE TEMPERATURE AND/OR
PRESSURE BUILD-UP WHICH CAN RESULT IN PROPERTY
DAMAGE, SERIOUS PERSONAL INJURY, OR DEATH.
E. Potable Expansion Tank
F. Scalding
Approximate Time / Temperature Relationships in Scalds
120
o
F
More than 5 minutes
125
o
F
1 1/2 to 2 minutes
130
o
F
About 30 seconds
135
o
F
About 10 seconds
140
o
F
Less than 5 seconds
145
o
F
Less than 3 seconds
150
o
F
About 1 1/2 seconds
155
o
F
About 1 second
Table 1 - Approximate Time / Temperature Relationships in Scalds
A water heating
system can deliver
scalding water. Be
careful
whenever
using hot water
to avoid scalding
injury.
Certain
appliances such as
dishwashers
and
automatic clothes
washers may require
increased
water
t e m p e r a t u r e s .
By setting the
thermostat
to
obtain the increased
water temperature
required by these
appliances you may
create the potential
for scald injury.
To protect against
injury, install a mixing valve in the water system. This valve
will reduce point of use discharge temperatures by mixing
cold and hot water in branch supply lines. Such valves are
available from your local plumbing supplier.
Table 3 details the relationship of water temperature and
time with regard to scald injury and may be used as a guide
in determining the safest water temperature for your
applications.
A potable hot water expansion tank may be required to offset
heated water expansion. If there is a back flow preventer or any
other type of no return or check valve in the system a thermal
expansion tank IS MANDATORY. The expansion tank must be
sized for the entire water volume of the hot water system. A
weeping relief valve indicates the need for an expansion tank.
See the Typical Expansion Tank example in the Piping section
for details.
valve is sized to the BTU/Hour capacity of the boiler. The T&P
valve must be plumbed down so discharge can exit at least 6”
above the structural floor. The relief line cannot be in contact
with any live electrical parts. If the relief valve constantly weeps
install an expansion tank. See expansion tank manufacturer’s
instructions for suggestions.
