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FILLING THE SYSTEM
The pH of a system is a measure of the hydrogen concentration. The higher the reading the more basic
the solution, the lower the PH the more acidic the solution. The pH scale ranges from 1-14 with a ph of 7
being neutral. The proper pH of a system can have a great effect on the overall life of the system. The pH
of a system should be kept between 9 and 10.5 for optimum operational life. Less than a 9pH will corrode
steel and a higher than 10.5 will corrode brass and copper. High pH will cause precipitation of iron from
the water that will cause corrosion in the system. Buffers and inhibitors can help maintain the proper pH
range.
System can be sick and show up in a change of the pH. A bacterial infection from injection water and
other sources can produce an acidic byproduct which will drop the pH. This can be combated with the
addition of a biocide. As glycol degrades, it produces acidic byproducts that drop the pH. The system
needs to be maintained annually by monitoring the pH of the solution with a pH meter or test strips
making adjustments as needed.
There are different types of bacteria that can infect a system. Bacterial infections are not often seen but
occasionally appear. They can take the form of slimy goo to looking like little paint chips they can plug
the heat chambers on the heat unit. Bacteria can thrive in a glycol environment that has less than a 20%
Glycol. At this lower concentration the glycol is no longer toxic to the bacteria and actually acts as food for
it. Bacteria can leave a slime residue that interferes with the operation of the system. The excrement of
the bacteria can be highly corrosive, as indicated by pin-hole leaks in the system. If an infection is found,
the best way to remove it is to add dispersants and a biocide to the system. Glycol and water mix should
be over 20% and under 50% adjusted for your local tempeture protection.
Conductivity is a indirect measurement of total dissolved solids in the water. Domestic tap water has a
conductivity of about 300 uS/cm The conductivity in a closed loop hydronic heating system should be
between 700 and 3200uS/cm depending on which additives are in the water. Addition of glycol, nitrite
and even soft water will have an effect on the amunt of disolved solids in the water. Conductivity above
3500uS/cm indicates a high level of dissolved solids water with large amunts of dissolved solids
becomes physically aggressive and can breakdown o-rings. Systems above 3500 uS/cm should be
flushed and refilled with fresh water/glycol and if required corrosion inhibitors.
The "Old School" of water quality recommended distilled, or soft water in closed loop systems. It was
thought that the precipitation of CaCo, needed to be controlled. It is now recommended that hard water
can be used. The reason for change is that softened and distilled water has the natural mineral balance
disturbed. The disturbed water will try to re-balance itself by leaching the minerals from the metals in the
water and from the system itself. The leaching of minerals from the metal will cause a higher rate of cor-
rosion. To help combat the precipitation of CaCo, with out softening the water, dispersants are included in
the corrosion inhibitor mixtures that keep the CaCo in the water. A concern arises with respect to hardness
in well water. Well water is very hard and in some cases up to 60 grains/USG or 1026ppm. In some areas
it also has bacteria as well as hardness. In cases of extreme hardness it is better to use city water.
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