Sacrificial anodes for our hot water storage tanks are
available rigid or flexible. They are made from magnesium alloy
rod, attached to a 1.25" MPT plug. One or more anodes weighing 25g
per sq ft of tank area are supplied with all Hanson glass lined
tanks and are optional with cement lining. They are not offered
with epoxy type linings as their action has been known to attack
the bond between the epoxy and the steel, causing blisters.
They are to be screwed tightly into carbon steel tappings in the
tank indicated on the shop drawing before a new tank is put into
service. If on the top of the tank they will normally be the flexible
style, made from 10" sections with stainless steel cable links.
Elsewhere they will be rigid, which are much easier to install in
a new tank if it is positioned so that the anode can be dropped
in vertically before the tank is set. When rigid anodes are being
replaced in service, the tank must be drained down to the level
of the anode before it is removed. This is not necessary with top
mounted anodes, but all valves must be closed and pumps switched
off in both cases. Extreme care must be taken when removing anodes
to avoid scalding.
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. If it is still in usable condition it can be cleaned and reinstalled. Residue in the bottom of the tank
must be cleaned out. As erosion of the anodes varies from tank to
tank, the inspection schedule should be adjusted to suit. A maximum
one year interval is recommended. When ordering replacement anodes,
please include the tank serial number which can be found on the
nameplate near the manway.