Yes. Iron will plug a R.O. membrane, as the membrane is not able to flush iron out. Trace amounts of iron (up to 2 PPM) can be removed by a water softener. If the water contains 1 PPM or less, there is no need for concern as the membrane will usually last 1-2 years. Note: This refers to clear water iron, not red iron. The difference is that clear water iron leaves no visible signs, whereas red iron leaves a reddish brown discoloration in toilet bowls, tanks, sinks and tubs. If red iron is present, steps to remove the iron will have to be taken, otherwise the warranty will be void.