I need a ladder in my underground water tank at home, to enable easy access for cleaning and maintenance operations. The water from the underground tank is used for drinking, apart from other household chores.
What would be the most suitable metal for this submerged ladder in the underground water tank? I don't want any water contamination due to sustained contact between ladder metal and tank water, as the water is used for drinking. TDS of water supply is ~125 mg/liter.
EDIT - I would also want to know any metal treatment (paint, varnish, etc) to prevent water contamination due to sustained contact between ladder metal and tank water.