The irony of the school bond issue facing Fairfax City residents Tuesday is that residents could end up paying more in taxes in the next few years if the $6.2 million to repair city schools is defeated than if it is approved, according to city officials.

If the bonds are defeated, the school board is expected to ask the city council to include $900,000 for school repairs in the fiscal 1984 budget that the council will adopt next Wednesday. The council was due to adopt the new budget on the day of the bond referendum, but postponed action a day to await the referendum results.

If the bonds are approved, the cost to the city in fiscal 1984 would be about $279,000--for half a year's interest--and about $650,000 a year for the remaining 20-year life of the bonds, according to city comptroller Jeff Cawley.

"The vast majority of the items in the bond referendum are mandatory things, not voluntary things, that must be done to the schools," Allen Griffith, a member of the City School Bond Committee that is urging approval of the bonds, said this week.

"Our position is that, yes, bonds are expensive, you pay interest for them, but they 20-year bonds allow future residents to help pay for the benefits in schools they and their children will enjoy."

The bonds would pay for repairs to almost all the schools (all but the high school are more than 20 years old), extending their life another 20 years. They also would eliminate building, health and fire code violations, repair plumbing and electrical systems, open schools to the handicapped, and add classroom and gym space to most of the buildings.

The top priority is expected to be replacing the roof on the 12-year-old Fairfax High School, which leaks badly. The leaks have damaged ceilings, walls, carpeting and library books, officials say. Replacing just the worst part of the roof will cost about $600,000, according to school superintendent Wayne White.

The city manager's proposed $24-million, 1984 budget calls for a 7-cent hike in the city's property tax rate of $1.15 per $100 of assessed value. Last week the council suggested some minor changes in the budget and advertised a possible 13-cent increase in the tax rate.

Under state law the town can adopt a lower tax rate than advertised but not a higher one.