keep in mind, to do those numbers you need a real RO/DI cart, not just the DI filter that some of guys use for small residential add-ons. The filter cost will kill you if you don't have the cart.
Agreed - resin can be expensive without the carbon/RO filters as well. I have a 4 stage commercial set-up. Fortunately too here in the area I live, we barely have 50-100 PPM in our public water supply.
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Brandon Vaughn
All-Clean! SoftWash Gresham, OR brandon@allcleansoftwash.com www.allcleansoftwash.com 503.887.6404