A strong, soaking rainfall in Pennsylvania is needed to reduce the high salinity levels in Harford's municipal water supplies, county administrators said.
The county issued a health warning to residents two weeks ago advising people on low-salt diets to use bottled water for drinking and cooking because of the high salinity levels.
Other people will not be affected by the amount of sodium and chloride in the water, although they will notice a salty taste, administrators said.
Because of the little rainfall over the past few months, salty water from Chesapeake Bay has backed up into the Susquehanna River, one of the county's main source of water supplies.
Water drawn from the river serves about 21,000 customers in Havre de Grace and other areas of the county.
About 3.8 million gallons of water is tapped from the Susquehanna daily.
The amount of sodium and chloride in the water has ranged between 100 and 180 parts per million during the last month.
The normal range is 35 and 50 parts per million, according to County Health Officer Thomas M. Thomas.