RESIDENTIAL ELECTRIC WATER HEATER
SERVICE HANDBOOK
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Technical Training Department 36 of 36 Residential Electric Svc Handbook
Ashland City, Tennessee ©2004 STC082
TECHNICAL BULLETIN
BULLETIN 52
LEAKING TEMPERATURE AND PRESSURE RELIEF VALVE
SYMPTOMS
Water seeping around the relief valve tank connection
Leakage at the threaded portion of the relief valve connection
Intermittent weeping and/or dribbling from the relief valve
Large volume of hot water sporadically discharged from the relief valve
GENERAL
The temperature and pressure relief valve (T & P) is a safety device limiting temperature
and pressure levels in a water heater. Each T & P has both a temperature and pressure
rating.
Normally, the temperature and pressure relief valve will have a temperature rating for
210F. A probe (part of the relief valve) extends into the tank measuring the stored water
temperature. This probe must be within the top six inches of the water heater. However, if
the water heater’s thermostat malfunctions, higher than normal water temperatures could be
produced. Once the probe senses a temperature exceeding its temperature rating, the relief
valve will open to full capacity releasing “very hot” water until the temperature is below its
reset temperature.
The pressure rating on the relief valve should be the same or less than the certified working
pressure of the tank (generally 150 psi) and be below the lowest pressure rating of any
system components. It is not acceptable to install a relief valve that exceeds the maximum
working pressure of the water heater. Once the pressure in the tank reaches the valve’s
pressure rating, it will slightly open relieving the pressure. Relieving of pressure can be
noted as “dribbling” or “weeping” water from the relief valve.
If an incorrectly sized temperature and pressure relief valve is installed, the warranty will be
void.
THE FIX
Seeping at the spud of the water heater
- Spuds are welded to the tank and are not
repairable. The heater should be replaced.
Leakage at the threaded relief valve connection
- Remove relief valve and reseal
connection.
Intermittent weeping and/or dribbling at the relief valve
- The relief valve relieves water
slowly when actuating on pressure. A closed system can cause pressure to increase in
the system. This condition is called thermal expansion. For additional information
regarding thermal expansion please see Bulletin 45.
Large volume of hot water sporadically discharged from the relief valve
- The relief valve
relieves water quickly when actuating on temperature. The only cause of this problem
is a malfunctioning thermostat.
(24 pages)
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