Why do you not recommend using galvanized pipe on your water softeners?

A question often asked is materials of construction for water softeners. Summarized below, Res-Kem's Director of Engineering, Bob Hader answers in a recent "Engineering Notes":

"Corrosion can occur with any type of piping depending on the application, environment and precautions taken to prevent corrosion. We at Res-Kem find that steel piping with iron fittings offers the best balance of corrosion resistance and cost.

First, softened water has not shown to cause any more internal corrosion in steel or galvanized piping than hard water. Corrosion, which does occur with unlined steel tanks, piping & fittings or galvanized tanks pipe & fittings is generally caused by other factors. Some of these are pH, temperature, dissolved gasses (oxygen and carbon dioxide) in the water, contact with air and galvanic action.

The greatest contributor to corrosion we see with water treatment equipment is on the exterior surface of tanks, pipe and fittings. Given most water treatment is in areas where the air is warm (boiler rooms, laundries, non-air conditioned utility rooms) and the water is cold; condensation forms on everything. Uncoated or unprotected steel tanks, steel piping and cast iron valves will rust and corrode. Galvanized piping is not free from this problem. The corrosion will take place at the threads (which are not galvanized)."

Here is the complete Engineering Note.

What is an Empty Bed Contact Time (EBCT)?

We receive many questions on calculating the Empty Bed Contact Time as follows: "How do I calculate the "Empty Bed Contact Time" for sizing my carbon bed?"

Our Answer:
Calculating the Empty Bed Contact Time, EBCT, is fairly easy to do once you know that the EBCT has the units of time, and usually presented in minutes. You need to know the volume of the carbon bed in your vessel and the flow rate. Just watch to be certain your units are consistent.

For the units commonly used in the United States:
V = Carbon Bed Volume (cubic feet)
Q = Flow Rate (gpm)
C = Conversion Factor (7.48 gallons/cubic foot)

EBCT= (V x C )/ Q

The EBCT for some common contaminants are:

Chlorine = 2 minutes
VOC's = 7 minutes
Hydrogen Sulfide = 4 minutes