Instead of washing your towels in hot temperatures, which wastes lots of energy, consider the following things. Firstly, it’s important to give them a chance to dry between uses. You could also try to dry them in the sunlight, since the UV-radiation kills lots of germs. If that’s not possible, you could also use a tumble dryer. In case the towels have been kept moist or are more heavily soiled, you might need to use 40 degrees, and in rare cases, where the towels are soiled with body fluids or if they’re used by persons who are ill, you should wash them in 60 degrees. It could also help to dry and iron the towels afterwards, since the heat kills bacteria.
One simple, but important, step to keep your towels from getting a fusty smell is to wash them often enough. A rule of thumb is to wash them after 4-6 uses. If your towels still have an unpleasant odour, try pre-treating them before washing. Soak them in a water bath with half a scoop of A+ powder detergent for one hour, then wash as instructed. Use an A+ powder detergent when you wash, since it contains enzymes and bleaching agents that counteract bacteria and helps eliminate bad odors.