Here's a great little setup, nothing big, but good for a car at a time. Works well as long as you understand how to use it, ie, final rinse only... I use it, recommend it. And for the cost, it's a deal. If doing multiple cars, some setup from Obsessed Garage might be in order.
Here's the deionizer...
https://www.amazon.com/gp/aw/d/B07H8...b_b_asin_title