I have recently had a rainwater tank installed and it is connected to my laundry.
How would I filter rainwater to substitute having to buy distilled water for certain applications like placing water in my clothes iron?
Distilled water is can be made. These instructions use common items so that you can envision this easier, not because you need those specific items.
The water is going to evaporate, leaving behind any debris in the pot. The water vapor will condense on the plastic wrap. As this distilled water collects, the slope of the wrap will cause it to flow to the center. Drops of water will form and eventually weigh do much as to fall off the wrap and into your cup.
It will take a long time, a couple of ounces a day, maybe. The idea is there, collect condensed water. A pressure cooker would probably work great for heating water. Attach a hose to the sream release and put a cup at the other end of the hose. You just have to be sure about your rate of condensation.
There is laboratory equipment made specifically for doing this type of thing.
Rainwater can hold dirt and other debris when it amkes contact with surfaces that are capturing the rain (roof etc)
You can always filter them using 2-3 coffee filters to filter out the debris, and then use that for your iron, and other applications that need to use 'distilled' water.