Many District tenants will begin paying slightly higher rents May 1 under a city government ruling that will allow landlords a 4.2 percent rent increase.

The District's rent control law covers 115,000 apartments, and 90 percent of the city's landlords usually take the annual increase allowed under the city's 1980 rent control law, according to rent administrator John Hampton. The amount of the annual increase is tied to changes in the area's consumer price index.

The rent increase, down from 8.9 percent in 1981, was announced by the District's rent control office in March. May 1 is the first day that the increase can take effect because tenants must be notified 30 days in advance of rent increases.

In a related development, more than two years after passage of the city's 1980 rent control law, the rent control commmission has proposed the first complete set of regulations for carrying out that law and reaching decisions on landlord petitions for rent hikes exceeding the increase and tenant petitions for rent decreases.

The new comprehensive regulations replace a series of partial regulations enacted by previous rent control commissions since 1974, when the District started its rent control program.

The incomplete set of regulations, some of which were hurriedly written, have led to delays in decisions, inconsistent decisions by the rent control office, backlogs and a deluge of appeals to the commission, say landlords and tenants. Until two years ago the commission was made up of nine part-time members; it now consists of three full-time commissioners.

Commission chairman Jacqueline Moore said the regulations were delayed because the new commission, which took office in August 1981, made as its first priority dispensing of a backlog of 269 cases that had been pending "for quite some time."

"The new regulations should make the processing of petitions much easier," Moore said. They are also expected to bring more uniformity to the decisions by the rent control office and the commission.

The major change proposed by the regulations would remove the rent administrator from making the final decision on tenant or landlord petitions, Moore said.

Under the old system, a hearing examiner would take testimony from landlords and tenants, then make a decision that went to the rent administrator, who would approve or disapprove it. If either a landlord or tenant was unhappy with the final decision, an appeal was filed with the rent control commission.

Moore said both tenants and landlords had criticized that system because it was unclear how the rent administrator was making decisions. "The rules did not require that any action taken by the rent administrator become a part of the public records," she said.

Therefore, neither landlords nor tenants knew if the administrator had read the transcript of hearings and looked at evidence presented because the administrator was not required to write a separate opinion but only accept or reject the opinion of the hearing examiner.

Under the proposed regulations the decisions of the hearing examiner would be final unless appealed to the commission and overturned by it, Moore said.

Both landlord and tenant groups are still studying the new regulations.

The commission will accept written comments from the public on the new regulations until April 30. If the commission makes no changes, the regulations will then go into effect.