Hanson Hot Water Storage Tank Maintenance


Water that contains dissolved oxygen is corrosive to carbon steel, more so when its temperature is above ambient. The tank shell, heads and connections will oxidize rapidly if they are not protected. Stainless steel fittings offer some protection. When they are in good condition tank linings prevent hot water from contacting the steel directly but they too are vulnerable to damage over time especially at elevated temperatures.

Linings should be inspected periodically and patched as necessary.

Anodes in glass lined tanks must be changed when required.

The purpose of anodes is to divert corrosive action away from any exposed carbon steel inside the tank. This is indicated by erosion of the anode, which should be replaced when it is 50% or more eroded. When it is reduced to less than 1″ in diameter, an anode has lost over 48% of its weight and should be replaced.

Our standard 1 5/16″ flexible anodes need 12″ clearance above the tank for this purpose. As they erode,residue might accumulate at the bottom of the tank. This should be cleaned out regularly as the area it covers is not protected by the anodes.

Epoxy linings are vulnerable to high temperatures, for example in solar heating systems. If possible, temperatures should be maintained well below the maximum of 180°F. Exceeding this temperature will cause severe blistering of the lining. Erosion of a cement lining can be rapid especially if high flow rates are experienced. Any scuffs on the outside of galvanized tanks should be touched up with a cold galvanizing spray and any residue inside the tank cleaned out from time to time.

If hot water is allowed to stagnate in a tank for long periods of time the water may acquire a brown tint. It is natural to assume that this is due to oxidation in the tank or piping but in fact it can also be caused by bacteria. Systems with constant flow rates do not experience this symptom.
Electrolysis can also erode tank steel if stray current in the building is allowed to pass through the vessel, which should be isolated to prevent it.
Dielectric isolators should be installed at the tank connections and checked periodically for effectiveness with an Ohmmeter. Zero current flow is the desired condition.

The area around the tank supports should be kept clean and free of clutter as this could also lead to stray current through the tank causing damage by electrolysis.

If the Ph level of the water remains between 6 and 8 and its Langelier Index calculation is around zero the service life of the vessel will be maximized. Information about these

measurements can be found on the internet.

  • External

Tanks that are installed outdoors are vulnerable to weather damage. Any cracks or gaps in the insulation must be repaired or caulked promptly to prevent moisture from penetrating and causing corrosion on the outside of the tank. Sprayed-on foam insulation can separate from the tank due to moisture entrapment and heat cycles.
A procedure to repair this damage on site is available.
In especially moist or humid conditions a Factory applied optional inorganic zinc rich primer is highly recommended but is beneficial in any environment.
Even though they are not vulnerable to weather damage, tanks installed indoors should also be examined from time to time for external corrosion due to condensation and leaks from connections or inspection openings. All accessible painted surfaces should be properly maintained.

  • General

An inspection and maintenance schedule should be set up for all hot water storage tanks in service. Depending on experience and service conditions, inspection intervals can be adjusted. Of course, any problems found should be rectified immediately. Non-scheduled inspections should also be carried out as conditions dictate. For example, outdoor tanks should be inspected promptly if extreme weather events take place.
Any questions concerning Hanson hot water storage tank maintenance can be sent to: info@hanson tank.com/ or by calling 800 421 9395 8am-4pm Mon/Fri Pacific Time.