While the cost of gasoline, food and housing continues to soar, Fairfax County residents will be able to drink public water during 1980 at last year's price -- 70 cents per 1,000 gallons.

The Fairfax County Water Authority made public last week its 1980 budget of $25.4 million which calls for no increase in water rates. Water sales are expected to account for $17.6 million, or 69 percent of the total budget.

The cost of Fairfax water appears to be a bargain. According to Jim Warfield, public information officer for the water authority, county customers are being billed according to a 10-year plan which has taken inflation into account.

Under this billing procedure, the water authority estimates the cost of water and operations during a 10-year period. Customers pay an inflated bill for the first few years, a bill reflecting actual water costs during the middle years and a low bill during the final years.

The authority drew up the plan in 1977 and has not raised water rates since.

"We hope we can keep water rates steady into the early 1980s," said Warfield.

Another key to the county's stable rate structure is the Farifax building boom since, according to Warfield, each new customer is required to pay a one-time hook-up fee to receive public water. Many other water commissions use quarterly water bills to all customers to subsidize the cost of new customers connecting into the system.

The water authority has scheduled a public hearing on the 1980 budget for Dec. 20 at 8 p.m. at its headquarters at 8560 Arlington Blvd., Merrifield.

Warfield says he expects the public hearing to be a repeat of last year's, when rates also remained the same -- no public and nothing to hear.