BULLETIN FROM....

Spring 1997

HOT WATER TANKS AND OTHER STORAGE TANKS WITH MANHOLE OPENINGS

It is recommended that hot water tanks and other storage tanks with manhole openings be drained and internally inspected every three to five years for cleaning and examination.

The following items are of particular concern:

1. Condition of stone lining (if applicable) and condition of the inner shell.

• If lining is cracked, flaked or spelling in some areas, localized pitting/corrosion will likely follow and repairs should take place as soon as possible.
• Vessel's inner shell must be checked for corrosion, pitting, thinning or cracking any abnormalities, if serious, must be addressed.

2. Condition of manhole gasket sealing surface. Corrosion around the manhole opening is usually caused by leakage past the gasket. It is, therefore, important to ensure no leakage exists to cause serious corrosion.

3. The connection opening to the safety relief valve should be checked to ensure it is clean and clear while the vessel is open.

4. The safety valve should be clear and free to open. It should be equipped with a testing lever, be of 3/4" pipe size minimum and have full size discharge piping. These important safety devices should be tested regularly (monthly) while vessel is in use.

• The safety relief valve should have a set pressure of no more than the maximum allowable working pressure rating of the vessel and have a rated capacity of at least the maximum Btu input of the appliance feeding the storage tank.

5. Leaks at any joint at the vessel or on piping will promote corrosion. Corrosion will cause metal and threads on piping and fittings to waste away. Necessary repairs or adjustments should be made to stop any leakage as soon as possible.

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