A.O. Smith TC-049-R2 manual Technical Bulletin, Service Handbook

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

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 210°F. 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.

A.O. Smith Water Products Company	59	Training Department
©2002		Ashland City, Tennessee