IT'S DIFFICULT these days, even under the best of circumstances, to buy a home - and for low- and moderate-income families, the difficulties are sometimes insurmountable. Often one of the stumbling blocks is the practice of "redlining" - discriminating on the part of some savings-and-loan institutions against giving mortgages in lower-income neighborhoods. While "redlining" is difficult to prove, almost everyone familiar with the business of handing out mortgages admits that the practice has gone on for some time - and that it takes unusual measures to eliminate it. Starting in January, the District will make a significant move toward getting rid of that practice, joining 16 other cities across the country that have each created a mechanism for families to receive a review of their application - and possibly a reconsideration in favor of financing.

The mechanism is called a mortgage-review committee. The formation of such a committee for the District was recently announced by T. William Blumenauer Jr., president of Columbia Federal Savings and Loan, who will be the committee's chairman. The committee is composed of four persons representing the "public interest" and four persons - plus a non-voting chairman - representing the savings-and-loan industry. They will review appeals from residents throughout the metropolitan area who have applied for mortgages of less than $75,000 and who believe that they have not been given fair consideration on their loan application.While having a case reviewed by the committee will not guarantee a favorable decision, home owners will get a chance to have their grievances aired in an impartial fashion. And although the committee has no official standing, it will represent all of the savings-and-loan institutions that have a home office in the city, plus one that is based in Maryland. That pretty much ensures that these institutions take this review procedure seriously, which may mean, in turn, that they will be more inclined to give applications unbiased attention in the first place.

Other review committees around the country have as erratic track record: Some operate exceedingly well, while others do very little. It seems to depend on two factors: the interest taken by the committee member themselves, and the willingness of those who want to be reconsidered for mortgages to make their desires known through filing an appeal. There's no doubt that going through the mortgage-application process once is a tedious and often cumbersome exercise, and that the notion of having to do it a second time - without guarantee of success - may be unappealing. But if "redlining" is to be eliminated, the review committee offers a way to start doing it. It may just be that number of people who thought home ownership was closed to them will find that they can have a second chance.