Butler County commissioners yesterday unanimously approved a change in the way it taxes county properties and started the process of notifying all property owners.

Commissioners approved a change in the property tax ratio, increasing it from 75 percent of 1969 market values to a full 100 percent.

Commissioners had agreed in May to advertise the ratio ordinance, making the new rate effective in January.

Ed Rupert, the director of property and revenue for the county, estimates that the county's millage rate would be reduced concurrently to 22.5 mills from the current rate of 30 mills, which is a combination of 25 mills for general purposes and 5 mills for debt service.

By changing the ratio and lowering the millage rate, the county would have more leverage to raise taxes without seeking court approval to exceed the 25-mill cap on the general purpose property tax rate.

Another option would have been a countywide reassessment, a proposal that was advocated at the board's public meeting yesterday by two former county commissioner candidates, Linda Volaric and Jim Eckstein, and W. L. Rodgers, a local attorney who said he has dealt with tax assessment issues in many Pennsylvania counties.

Commissioners do not favor reassessment, a proposal they estimate could cost $8 million.

By state law, the county and municipalities within it are limited to a 5 percent increase in the first year following a ratio change, while school districts generally can raise taxes by 10 percent.

The ratio was last changed in 1982 when it was increased from 33.3 percent to the current 75 percent.

Commissioners hired Government Services Software Inc., of Honesdale, to send out notices to property owners. The cost will be about $49,000. There are about 105,000 separate properties in the county.

Commissioners Chairman Dale Pinkerton acknowledged that "taxes eventually will go up," but he said the commissioners are committed to trying "as hard as we can to keep taxes as low as we can for as long as we can."