Water Heater 

It seems like almost every home inspected has at least one problem at the water heater. Most of the time, the problems are not with the water heater itself, but various installation problems. The most common problem deals with the Temperature and Pressure (T&P) Relief Valve and drain line, so we will start there. The T&P valve is located at the top, or on the side near the top of the water heater. It is a safety device that is designed to open and release pressure, steam, and hot water if the water heater overheats. If the pressure is not relieved, the tank can explode. The temperature and pressure that will cause the T&P valve to open is printed on a tag attached to the valve. Almost all residential water heater T&P valves will open if the temperature reaches 210°F, or if the pressure reaches 150 PSI. The T&P valve must also be able to release the pressure as fast as the water heater can generate it, so the pressure can’t continue to increase. So on most residential water heaters, the T&P valve has a ¾” opening. There needs to be a drain line attached to the T&P valve to carry the hot water, steam, and pressure away. This drain line is where most of the problems are observed. The inspection standards of practice only require that the T&P drain line be “properly installed”. We have to look to other sources to define what is “proper”. The local building codes and plumbing codes currently allow a CPVC plastic drain line. As a result, most of the current water heater installations in this area have a CPVC drain line. However, most of the water heater manufacturer’s installation instructions specify that the drain line be of a material able to withstand 210°F and 150 PSI. CPVC plastic pipe is only rated for 180°F and 100 PSI. My recommendation is that the T&P drain line be metal, usually copper, where it is connected to the T&P valve and extending for at least 18” – preferably for the full length of the drain line. This will help prevent the continuous heat at the water heater connection from degrading the drain line material, and hopefully will prevent failure of the drain line if the T&P valve were to open. In any installation, whether the T&P drain line is copper or CPVC, it should not be reduced in size. A ¾” T&P valve must have a ¾” drain line. The drain line also must go downhill all the way to its termination. The reason for this is that water trapped in an uphill section of the pipe can block the release of pressure if the valve opens. Also, if the drain line runs above the T&P valve, water will back-up to the valve and it may corrode the valve so that it does not open. The other common problems at water heaters can be covered quickly. Any water heater installed in the garage or in a garage closet needs to be elevated a minimum of 18” above the floor of the garage. This is because gasoline fumes tend to accumulate near the floor, and can be ignited by the water heater. This applies also to electric water heaters, because the thermostat contact at the lower heating element produces a small spark. Gas water heaters need to be connected with an approved gas supply line. Approved types are usually either flexible stainless steel (silver colored), or a flexible gray vinyl. Copper or flexible brass gas supply lines have been used in the past but are no longer approved.  A shut-off valve is recommended on the cold water line supplying the water heater. This is so the hot water system can be shut off if it develops problems, or while repairs are being made, and the cold water can remain turned on. [ Back to General Home Information ] Schedule Your Inspection Today