We have hard water, I mean really hard water. The Grains per Gallon water hardness scale is 15 when I called our water supply utility company. Our dishes were cloudy, and I was looking for solutions, so I called to get the grains per gallon so I could refer to the dishwasher manufacturer’s recommendations on how much detergent to use. They recommended filling both cups completely. We did, it helped. But we go through a LOT of dishwashing detergent this way.
Yes, we bought it at Costco, the Kirkland brand. And yes, it was much cheaper than buying from the grocery store. But we were still using a LOT of detergent, and I looked for something I could make, as I had been having great luck with my homemade cleansers.
Homemade detergents did NOT work for us. It was horrible, talk about a white film on everything! We tried mixtures of borax and baking soda, borax and washing soda, all three mixed together, etc. The only thing that I did find helpful was vinegar in the rinse agent dispenser when we used our regular detergent.
I blame our hard water. I read many other reviews of people that borax and baking soda worked just fine for. Now, we are using the Finish tabs that we can buy in a huge box at Costco, as these last us longer than the same cost of liquid detergent, with vinegar in the rinse. And our dishes, glassware, bottles, etc. come out clean and relatively free of hard water build-up.