TSP (Trisodium Phosphate) in Your Dishwasher

In recent years, many of us who use automatic dishwashers have been disappointed with the results. Instead of coming out gleaming and spotless, as they used to do years ago, our dishes and silverware come out with a dull film all over them. In hard water areas, the machine itself builds up a mineral film over time.

It turns out that the reason is a political decision based on pseudoscience. In a well-intentioned effort to prevent algal blooms in water which can result in fish kills, governments have restricted or forbidden the use of phosphates in automatic dishwasher detergents. So now, we are forced to use ineffective phosphate-free detergents which do a poor job of cleaning food residue off our dishes and leave a dull film behind. We're not really doing the fish any good, either, because by far the greatest source of phosphate in water is agricultural runoff, both from chemical fertilizer (the P in N-P-K fertilizer is phosphate) and from animal manure. The amount we add by using a small amount of TSP in our dishwashers is negligible.

The solution is very simple. Go to the nearest store with a paint department and pick up a box of TSP (trisodium phosphate). Get the smallest size, which is a 1-lb box. It'll last you a long time, and it's easy to store. Also pick up a box of 1-quart ziplock bags if you don't already have some. The TSP box has no spout, so you'll need to cut the corner off for easy dispensing. Then, since you'll want to protect the contents, you can store the opened TSP box in a closed 1-quart ziplock bag between uses. When you run your dishwasher, fill both cups in the detergent dispenser with your favorite detergent -- powder or gel -- as you normally do, then pour approximately 1/4 teaspoonful of TSP on top of the detergent in each cup. Close the cups and start the machine normally. That's all there is to it.

Before washing any dishes, I ran one cycle with an empty machine in order to clean out the mineral residue which had built up inside. I won't say that step is strictly necessary, but if you have a noticeable film inside the machine, it's certainly a good idea. Let it go through all the rinse cycles, but stop it before it starts to dry.

Now put in a load of dishes and run another cycle with TSP-fortified detergent.

When the dishwasher completes its cycle, compare the results with those you were getting without the TSP. You should see a dramatic difference.

In an area with extremely hard water, you may need to add as much as 1/2 teaspoonful of TSP to each cup, but certainly no more than that. Our water in this area comes from the Cumberland River, and is fairly hard because of dissolved calcium salts. Even so, I find that 1/4 teaspoon per dispenser cup does an excellent job.

Remember that TSP is a powerful chemical, so don't get it on your skin, and keep it away from children. If you should get any on your skin, wash it off immediately with large quantities of water. There's no need to be concerned about any residue on your dishes, though. TSP is highly water-soluble, so every bit of it will be rinsed down the drain along with the detergent.