Vent Condensation - A.O. Smith BTH 120 Series Service Handbook

VENT CONDENSATION

Failure to properly install the drain line on the condensate elbow will result in a water heater shut
down and a "blocked exhaust" fault message.
The average dew point of natural gas flue products is 127 °F (53 °C) . Propane flue products is 119 °F (48
°C). With 70 °F (21 °C) ambient air temperature and 180 °F (82 °C) stored water temperature, exhaust gas
will be approximately 140 °F (60 °C) .
Q. CAN I DRAIN THIS CONDENSATION TO THE FLOOR DRAIN?
A. Yes, this condensation can be drained to the 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."
Q. HOW DO THE PH VALUES OF CONDENSATE AND CARBONATED COLA DRINK COMPARE?
A. The pH of the BTH condensate average 4.5 which is approximately 4 times less concentrated than the
limit of 4.3 recommended 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 BTH condensate.
Q. WHAT DOES THE PH SCALE MEAN?
A. The PH value is a measure of acidity or 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.
Q. WHAT ABOUT CONDENSATE NEUTRALIZERS?
A. Condensate neutralizers are usually not necessary. 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 equipment. 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.
6" x 4" REDUCER
FIELD SUPPLIED
4" PIPE FIELD
SUPPLIED
EXHAUST ELBOW
VENT CONNECTION
FACTORY INSTALLED
VENT (EXHAUST) CONNECTION
Servicing should only be performed by a Qualified Service Technician
6" PIPE FIELD
SUPPLIED
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