There's another scientific truth that water poured down on the Lingam isn't considered holy water or "Theertham". Shiva Lingam's considered to be an atom model. There's radiation from Lingam as it's made out of a type of granite stone. Granite's a source of radiation (containing radium, uranium and thorium) & reported to have higher radio activity thus raising some concerns about their safety. This may be why disciples are told not to touch water that is poured down on the Lingam.