Starting Tuesday, every existing home listed for sale with the Colquitt-Carruthers real estate firm here will carry a one-year warranty against defects that may develop in heating and cooling, electrical, and plumbing systems as well as built-in appliances.

Owners who want to sell houses through that firm must purchase a buyer-seller protection premium for $220, a cost the seller may or may not be able to pass on to the buyer at settlement.

Colquitt will become the first major realtor here to make warranties mandatory - in an experiment the firm hopes will increase sales. In the past couple months a score of smaller real estate brokers here have jumped onto the warranty bandwagon, although none has gone so far as to make it a condition of sale. Colquitt officials think they may succeed in increasing consumer confidence - and sell more homes for more attractive prices.

Such a warranty might have helped Helen and John French of Waynesboro, Va. As she recalled in an interview, "It was our first home and we were very naive. We had the termite man and the electricity man go through the house we chose. But we didn't check the plumbing or septic tank because the owner said they were okay."

At the time of the Frenches' inspection, a wood fire was burning in the fireplace and something succulent was cooking on the stove. It wasn't until after the contract was signed and the house vacated that they noticed tell-tale stains and smells in the rec room where a pipe had broken when the house settled. Because they refused to go to settlement, the Frenches were sued by the owner and the realtor. They eventually won, but it cost them $2,000 in legal fees and other expenses.

Many warranties do not cover septic tanks, so the buyer should shop carefully.

A warranty did help Laurence Feder of Fairfax. He said it was "the best $175 I ever spent." The home inspection man had overlooked some rotten siding on the house, and the kitchen floor turned out to be rotten as well.

"In the end it was better they didn't catch it before," Feder said, "because if they had, I would have gone to the owner and offered to split the cost of repairing it." Feder collected $1,115 from Certified Home Inspection Program (CHIP), the company that had issued a warranty on the house.

The home warranty history begins with the Housing Act of 1954, which required all new homes purchases with mortgages guaranteed by the federal government to carry a one-year written warranty. In recent years the possibility that the federal program might be extended to the private sector has prompted some private companies to come up with their own programs for new and existing homes with conventional mortgages.

Acceptance by the public has been slow. There are no statistics, but one industry guess is 100,000 warranties were sold last year. Virginia H. Knauer, former White House consumer affairs adviser, put the blame on industry: "The industry has been lax in educating the potential home purchaser about the differences in home warranties and thus has done little to alleviate the consumer's confusion about what a home warranty means. The result, as I see it, has been to lessen the impact warranties offer as a marketing device and, at the same time, to create expectations on the part of the consumer that can't be realized."

Another reason Knauer saw for dissatisfaction was the lack of a formal complaint mechanism for customers of companies selling warranties on resale homes.

Take the case of Carol and Thomas Cochran who bought a 70-year-old house in Arlington. Included in the sale price was a $250 warranty with Electronic Realty Associates (ERA). When the shower leaked, the stall's tiling had to be removed to repair the metal shield underneath.

ERA at first refused to pay for the tile replacement because the work was "cosmetic." The Cochrans appealed to the Arlington County Consumer Affairs Commission, which intervened with ERA and finally succeeded in getting ERA to reimburse the couple.

After the National Association of Home Builders established a warranty program for new houses in 1974, the National Association of Realtors launched one of existing homes, which represent over 90 per cent of the 3 million dwellings sold annually nationwide. The NAR program, based on inspection, calls for replacement of heating, plumbing, electrical and cooling systems and repair of interior and exterior walls, floors and ceilings unless excluded from warranty.

For example, if a qualified inspector - such as an engineer, architect, or builder - decides your furnace has already outlived its normal life expectancy, it will not be replaced free in case of a breakdown. Under the non-inspection or insurance-type warranty offered by four out of the five members of the National Home Warranty Association, that furnace would be replaced free (excluding the deductible) if it were found in working order at the time of the sale, no matter what its life expectancy was.

Such a program is based on actuarial principles; the warranty company is gambling that the furnace will not break down in the first year despite its age.

NAR believes the inspection program is superior because it requires disclosure of the condition of the house to both seller and buyer, eliminating unpleasant surprises. Thus, the buyer may not be able to get that furnace warrantied, but with the knowledge of its condition, theoretically a lower price can be negotiated for the house.

Moreover, inspection plans cover structure whereas most insurance-type plans do not. Roof defects are said to be the most frequent and costly defect.

Proponents of non-inspection plans claim inspection is outmoded and unsalable. Bruce Grewell, who last year quit CHIP to go with American Home Shield, an insurance-type firm, believes there is no market in today's economy for inspection warranties.

"A seller doesn't want defects known before a sale and the price negotiated down; neither does the realtor whose commission will be diminished. On the other hand, because housing is so scarce (in California where he works), the buyer is afraid that if he tries to bargain the price down after getting an inspection report, someone else without one will be willing to pay more and consequently get the house."

Both types of programs cost about the same - $200 to $250 - although the extent of coverage and deductibles vary with each company. Neither program duplicates coverage against fire, flood or acts of God provided by homeowner insurance. Many deal directly with contractors on receipt of a phone call from the homeowner; others prefer to reimburse the customer when the contractor of his choice has completed the repairs.

Inspection has been more traditional in the Northeast than in other parts of the country because its houses are often older and its natives warier, one inspector maintains.So when the warranty concept was developed, it was grafted onto existing inspection programs in many cases. Other warranty programs were begun by insurance companies which then contracted with building inspectors.

Certified Homes Corporation of Columbia, Md., successor to National Home Inspection Service of Silver Spring, introduced its CHIP plan four years ago. In that time it has made 15-20,000 inspections and written 12,000 to 15,000 warranties, according to president Cary Cooper. A fifth of CHIP's business is done in the Baltimore-Washington corridor, and 85 per cent of the warranties are purchased by buyers. It is the only NAR-approved company operating here, although there are numbers of other inspection companies in the area.

At first CHIP warranties were mandatory, but now an inspection client can opt not to buy the warranty. CHIP has all but ceased writing in California, and Cooper admits the company is taking "a less aggressive approach on expansion" until the new government study on warranty programs becomes available.

The study, due this June, calls for the Department of Housing and Urban Development to recommend to Congress ways "for protecting home buyers from hidden or undisclosed defects seriously affecting the use and livability of the home." It will seek to determine the need and demand for a national system of home warranties and inspections and its likely impact on existing private warranty programs. A low-cost federal program could price private companies out of the market, so they are awaiting the report anxiously.

Of the four other NAR-approved inspection companies to be investigated by HUD, three are either not yet operating or are just test marketing Memphis-based Factfinder has already ceased writing new business for the time. St. Paul Home Protection Program, a division of the St. Paul Fire & Marine Insurance Co., operates only in Colorado. Its warranty director, R. L. Ramstead, said the number of policies sold the first year was "not successful," a fact he attributes to the newness of the program.

Ramstead also cited the public's memory of bankrupt warranty companies like Palace Guard of Milwaukee. Insurance companies selling warranties come under stringent state regulation which governs the amount of reserve cash they must keep. Warranty companies not backed by insurance companies are subject to no such regulation, which has led to some failures. Unregulated firms refer to their warranties as contracts rather than policies because they are not licensed to write insurance.

While the inspection-type companies appear to be retrenching or holding, the non-inspection types seem to be expanding. Since November, American Home Shield, based in Pleasanton, Calif., has signed up Colquitt-Carruthers Electronic Realty Associates of Kansas City, Kan., has signed a dozen realtors in Maryland and Virginia; and American Home Guard of Pigeon Forge, Tenn., has signed three in Virginia.

Contractual arrangements between the warrantors and the realtors sometimes include a membership fee giving the realtor the right to advertize the coverage and sometimes a processing fee. For example, the wholesale cost to the realtor of ERA's warranty is $180, to which the broker adds $60 to cover costs and profits.