That sounds a little high for RO, I see about 8-15 from store bought RO. I don't understand why you'd have problems with RO at 20-30ppm, but it's recommended to use a water softener before the RO filter.
"If your water sample shows that you have hardness, iron and sodium in your water, a softener needs to go in front of the RO system to remove the Calcium and Iron from the water. Otherwise the Calcium and Iron will quickly exhaust the RO Membrane."
If you have a water softener in your home, you may feel pretty good about your water. But in fact, even after being processed by a water softener, impurities may remain in the water you drink and w…
blog.watertech.com