I am doing some research to decide if a stainless steel water heater is right for my next water heater replacement. The trending opinion I find as I google around is that stainless steel is superior in terms of preventing galvanic corrosion (some models don't even use anode rods), but is also susceptible to premature death if the water's chloride levels are too high.

I pulled up my city's water quality report, and I am wondering exactly what values I should look at and what is the threshold for "too high"? Is it just the chlorine and chlorite ppm values to be concerned with, or other metrics as well?

In addition, I know that the stainless steel is resistant to galvanic corrosion, but what about the copper pipes connected to the water heater? Are those going to suffer from corrosion without an anode rod?

  • Chlorine rarely turns up in water sources. It is added by the city to arrest bacterial growth. One problem is that things like water heaters is corrosion has the side-effect of removing the chlorine, then the warmth creates a rich breeding ground for the things chlorine are there to kill. You must run them scalding hot to prevent this (upside: longer showers since you are using less hot). TLDR: tanked heaters are problematic. Dec 4 '17 at 17:08

Austenitic stainless steel ( non-magnetic) is unlikely to crack with chloride less than 100 ppm. Ferritic stainless ( magnetic - most auto exhaust pipes) will not crack in chlorides. Typical potable water is not corrosive to stainless or copper so galvanic corrosion would only be a problem in you also have plain steel. Although I believe "regular" water heaters are the most practical.

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