It’s annoying when powdered laundry detergent soap doesn’t dissolve completely. However, I’ve devised a pretty good method to making sure it usually does. My method works best for top loading washing machines. Before putting any clothes into the washer, I put the soap towards the back only (where the water that falls out will hit it instantly). After adding the soap, I then put a small amount of vinegar in there (vinegar is good for killing any smells in laundry as well), as this will help dissolve the soap a little faster. I then turn the water setting to hot and let it fill up about two to four inches. If I’m washing dark clothes I then turn it to cold and let it fill up halfway or more so that the water temperature drops. I find that the cheapest laundry detergent brands like Foca and Roma (that you can get at Wal-Mart) pretty much require this method. Another thing that helps is to make sure that the soap doesn’t have any clumps, balls or huge masses stuck together. If it does break them down or smash them before adding vinegar or turning on the water. Another thing I’ve noticed is that Wal-Mart is pretty good about showing cost per ounce on grocery items, but when it comes to laundry detergent they don’t. Bring a calculator with you, but from what I’ve found its hard to beat the Roma and Foca bags of detergent in price.