Copper Hot Water Tank - Green Stain
One year ago I purchased a house built in the 1950's that has copper plumbing and a copper hot water tank (electric). The house is fitted with a water softener that also removes chlorine from the water.
Recently, I've noticed that the tile floor of the shower develops a green tinted slightly sticky substance which can be removed with a soft scrub product. I have also noticed that the bath tub in another bathroom has a green drip stain that appears to have developed over many years (it was there when I bought the house). Using a soft scrub product doesn't remove it.
Does anyone know what is causing this green substance to appear? I'm assuming it is coming from the hot water tank but I'm not sure. Do copper hot water tanks need any sort of clean/flush maintenance? I've beed told that a copper hot water tank will "last forever", but no one has mentioned maintenance.
Thanks in advance for your help.