if hes using city water my thoughts on red roots is the water he is using is high in iron and maybe chlorine. iron and chlorine make an ionic compound. red iron oxide. rust.
we experienced this RED phenomenon when I worked in the laundry business. White sheets turning orange bec the chlorine bleach was causing the iron in the water to fall out and the tiny particles collected in the fibers. We had to start using 12% hydrogen peroxide based chemicals and no use sodium hypochlorite based products. The Orange sheets problem solved
Could also have a lot of iron bacteria if hes using well water. Its got to do with his water.