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SUF SERVICE HANDBOOK
INSTALLATION
Technical Training Department State Water Heaters
STC-077
14 Ashland City, Tennessee © 2004
CONDENSATION
The average dewpoint of natural gas flue products is 127° F. Propane flue products is 119° F. With
70° F ambient air temperature and 180° F stored water temperature, exhaust gas will be approxi-
mately 140° F. Recommended starting point for water storage is 120° F.
The extra high thermal efficiency of the SUF will result in condensation in the flue passage. The fol-
lowing answers common questions about this condensation.
CAN I DRAIN THIS CONDENSATION TO A FLOOR DRAIN? The “Corrosion Resistance of Cast
Iron Soil Pipe” by the Ductile Metals Association (formally the Cast Iron Soil Pipe Institute) states
that:
“Internal corrosion of cast iron soil pipe and fittings can be caused by strong acids or other reagents
having an acidity of pH 4.3 or less if allowed to contact cast iron pipe for an extended period of time
without sufficient dilution to raise the pH valve about 4.3. By avoiding low pH discharges, internal
corrosion problems can be limited or eliminated, assuring the owner many years of service.”
WHAT ABOUT THE pH VALUES OF CONDENSATE AND SODA POP? The pH of the SUF con-
densate average 4.5 which is approximately 4 times less concentrated than the limit of 4.3 recom-
mended by the DMA. Any water flow in the drain rapidly dilutes the condensate even more. A can
of leading carbonated cola drink measured a pH of 2.5 which is 300 times more concentrated than
the SUF condensate.
WHAT DOES THE pH SCALE MEAN? The pH value is a measure of acidity of alkalinity. A pH of
7 is neutral. Numbers from 7 to 1 indicate increasing acidity and numbers from 7 to 14 indicate
increasing alkalinity. The pH scale is similar to the Richter scale used to measure earthquakes.
Each number indicates a change of 10 times the concentration of the previous value. A pH 6 is 10
times more concentrated than a pH 7, a pH 5 is (10x10) 100 times pH 7 and pH 4 is (10x10x10)
1,000 times pH 7, etc.
WHAT ABOUT CONDENSATE NEUTRALIZERS? Condensate neutralizers are usually not nec-
essary. A condensate neutralizer is easy to make by filling a short length of 2” or 3” PVC pipe with
landscape marble chips, capping it and installing it in series with the condensate drain of the equip-
ment. Most commercial neutralizers are off the market because of poor demand for the product.
Condensation from the exhaust vent piping and tank internal flue way must be allowed to drain. A
“blocked flue” indication will often be your first indication that condensate is not draining.