I hate powders that don't dissolve fully and normally I will stop using them over that. Some powders are too dense to be put in a Hydroforce, especially if you're using it at 1:8 or 1:9. You're trying to put a whole lot of powder, enough to make over 11 gallons or over 44 quarts of prespray, into 5 quarts of water. Doesn't always work. If it won't dissolve completely in pretty hot water something is definitely wrong. It could be you're trying to put too much into that 5 quart container and the amount of powder just can't dissolve completely. You might try backing off a little on the amount of scoops. Maybe knock off 1 scoop and see if it still performs well and if it dissolves better. If you're using the 1:8 Hydroforce you may have to go 1:4. I've only had to do that with certain enzymes in the past that simply were too dense to put in a 1:8 at the recommended dilution. If it does not dissolve fully using it at the 1:4 dilution I'd be looking for a different prespray.