The signs are being installed where supplied water has not been treated or tested for quality.
Director of operations and planning Darryl Lew said this week the new signage was a legal requirement of the building code.
"The building code states that for any water supply that is not potable, a non-potable symbol must be positioned adjacent to the outlet.
"In addition to our legal requirements, the new signage will reduce the risk of visitors and staff getting ill as a result of drinking untreated water that could be contaminated."
Mr Lew said at many Doc huts, the water was collected from the roof and contained in tanks.
"Roof water can be contaminated by faeces from possums, birds and other animals and there could be dead animals in tanks or frogs living in them."
Mr Lew said Doc did not have records of people getting sick from Doc-supplied drinking water.
Priority was being given to Great Walk and "front country" sites. About half now had signs.
Signs will be installed at back-country sites within the next four years.
"At some of our busier visitor sites and campgrounds, water is treated and regularly tested but it’s not practicable for us to treat water at every hut, campsite and other Doc facilities," Mr Lew said.
That was particularly the case for facilities in remote locations that had low visitor numbers and few visits from staff.
One tramper told the Otago Daily Times he planned to ignore the signs, and he suggested others do the same.
"A greater worry is that the new policy may mean that Doc will no longer take steps to ensure that drinking water is safe, and point to the signs if trampers or campers get ill.
"However, the fact that Doc staff and volunteers regularly drink this water should hopefully help ensure they continue to have an incentive to ensure its quality."
Another suggested it might be time for trampers to carry a screwdriver "to save the backcountry from humourless warning signs" while others believed it would just waste Doc’s time and money.
