The problem with pure water is that it should only be drunk staight after production or should have been stored in an air tight container,
The Merlin was designed for domestic use so that pure water can be had on demand other ro's have to store the water in an air tight container's
Because it is pure there are no chemicals present to stop bacteria growing,(nasty little things some of these can be)
When I first started useing pure water I would drink the stuff, I was lucky the worst I got was a sore throut,I still drink the stuff but I fill a bottle straight from the Ro and only keep it for that day