Water Heater Dip Tubes-Why all the Fuss?
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Re-printed from Opflow magazine, distributed by the American Water Works
Association (AWWA). They may be reached online at http://www.awwa.org.
by Danny T. Hutchins, PhD
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In 1995, the Charter Township of Clinton (Mich.)
Water and Sewer Department investigated complaints at an apartment
building for seniors. In two apartments, tenants had found small,
white or light green-tinted particles in their aerators and strainers and
had problems with pressure and flow in their hot water supplies.
The investigating crew removed strainer screens in the
dishwasher, the aerator screen on the kitchen sink, and the showerhead
in both apartments.
In the first apartment, the sink aerator was plugged with white granular or
eggshell-like particles. The tenant said she had to clean the aerator every
other day. She also said the sink fixture had become plugged so badly
that it had to be completely taken apart. Water to her washing machine
and dishwasher had been completely blocked. The crew found that the hot-
water temperature at the kitchen sink was 141°F(60°C).
In the second apartment, the
sink aerator and the showerhead were partially plugged with the
particles. The tenant said that he often ran out of hot water much
more quickly than when he had first moved into the apartment.
The hot-water temperature at the kitchen sink was 128°F(53°C).
Samples of the particles and the hot and cold water were collected
from both apartments. Initially, the particulate material collected
was tested to determine what percentage of the sample if any, consisted of
calcium or magnesium. No calcium or magnesium was found.
Portions of the sample were observed through a surface microscope at 100
x, 1,000 x, and 1,500 x. Pieces of the sample had smooth sides and a
non-crystalline structure. Further analysis indicated that the sample was some type of plastic. To
validate the analysis, it was decided to remove and dissect one of the two
water heaters.
The mechanical staff removed the hot-water
heater from one of the apartments and replaced it with a 40-gal(150-L)
heater. The crew also cleaned the strainers in the dishwasher and
washing machine and the aerators in the kitchen, lavatory, and shower
fixtures.
Water Heater Autopsy
The water heater was cut open to analyze the epoxy lining,
dip tube, drain plug, and any plastic plugs, washers, or seals that might
have been used as part of the heater's construction. As soon as the
heater tank was opened, it was obvious that the dip tube was
missing. The epoxy coating was intact but exhibited serious
damage. On the tank wall were a dozen spots where a white,
oatmeal-like paste was the same plastic material taken from the apartment
aerators.
In the bottom of the heater, larger pieces of tube were
found. When examined, several of the pieces crumbled into a
grain-like mush. Analysis of the tube-shaped pieces and the
oatmeal-like paste showed that they were the same material as the samples
collected from the aerators and strainers-plastic dip tube.
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