I'm sorry, but your plumber has no clue. If the water softener had caused the water heater failure, which is extremely unlikely unless it's not working at all, then a tankless water heater will fail even faster. Your plumber will certainly make more money for less work with a tankless.

Since your water heaters have failed quickly, you ought to get your water tested to see if there is an inherent corrosion problem. At a minimum: pH, TDS, alkalinity, hardness (of your raw water before the softener and treated water after the softener). If the pH is really high, check silica as well.

We are on city water and it is quite hard.

where can I get a sample of my water checked?

If I do have water issues in the sample, how are these water problems treated?

thank you.

A couple months ago I replaced a 20 year old A.O. smith LP WH that was still working properly. I replaced it because I wanted to get the last of the "old" style WHers and not the "new" style ones down the road when I needed a new wH.

My water is 45 gpg hard and the water is softened.

Get a comprehensive test of your water at the house not a years old water quantity report from the water authority. with those results you'll see what needs to be treated and then decide IF your present softener is treating all the problems and is correctly sized for your water conditions and water usage and is actually working.

When you have water quality problems call a water treatment professional and when the plumbing is leaking call a plumber.

I concur with alice and would like to add,those kind of plumbers should be run out of town.

Thanks everyone. I appreciate the feedback. I will let you know what we decide.