I have used trisodium phosphate for roof cleanings and concrete before but I heard its not good with metal or painted wood. So I always avoided that and washed the house or gutters with a different solution. Is this true? Does it stain wood and damage metal? Am I wasting time using two different mixes? It was widely used in detergents before the phosphate entered the water supply. Since most sinks, dish washers and laundry machines are made of metal it doesnt add up.