Dunkirk H2OI Single Coil Stainless Steel Indirect Water Heaters - Manual (Page 20)

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VI. Maintenance
The water heater is intended to provide many years of reliable service. Components, such as thermostats and relief
valves, may be subject to failures that require service. Depending on the quality of the water supply, sediment and/or
scale may coat the heating coil in the tank and reduce hot water recovery rate. Failure to use the correct procedures or
parts can result in unsafe operation.
The owner should arrange to have the following inspections and simple maintenance procedures done at the suggested
frequencies.
1. Boiler and Domestic Water Piping (Annual)
Check all piping for signs of leakage at the joints, unions and shut-off valves. Repair as required.
2. Temperature and Pressure Relief Valve (Annual)
• The temperature and pressure relief valve should be checked to ensure that it is in operating condition. To
check the relief valve, lift the lever at the end of the valve several times. The valve should seat properly and
operate freely. If water does not flow, remove and inspect for obstructions or corrosion. Replace with a new
valve of the recommended capacity as necessary. Do not attempt to repair the valve, as this could result in
improper operation and a tank explosion. In areas with poor water conditions, it may be necessary to inspect
the temperature and pressure relief valve more often than once a year.
CAUTION
Before manually operating the valve, make sure that a drain line has been attached to the valve to direct the
discharge to an open drain. Failure to take this precaution could mean contact with extremely hot water discharging
from the valve during this checking operation.
If the temperature and pressure relief valve on the heater discharges periodically or continuously, it may be due
to thermal expansion of water in a closed water supply system, or it may be due to a faulty relief valve. Thermal
expansion is the normal response of water when it is heated. In a closed system, thermal expansion will cause the
system pressure to build until the relief valve actuation pressure is equaled. Then the relief valve will open, allowing
some water to escape, slightly lowering the pressure. Contact your water supplier or local plumbing inspector on
how to control this situation.
3. Sediment (Annual except where harsh water quality may require more frequent service)
Depending on water conditions, a varying amount of sediment may collect in the tank. Levels requiring service
are indicated by a small temperature difference between the boiler supply and return lines, and a reduced
recovery rate. Repeated flushing usually clears such material. As a preventive measure, water should be drawn
from the drain valve until it runs clear and the installation of a water filter should be considered.
4. Scale (Annual)
Hard water may cause scale buildup on the outside of the heating coil inside the tank. A water softener will
prevent this problem. Symptoms are identical to sediment buildup. If repeated flushing does not resolve the
problem, chemical cleaning may be required. Contact a qualified contractor.