Congress did the only responsible thing this week when it killed a costly new plan to provide health care at home for 31 million elderly and disabled Americans.

Despite the bill's defeat, the country hasn't heard the last of this exorbitant scheme. The public can count on the measure's being re-introduced after the November elections are over and the nation's lawmakers feel they don't have to worry quite so much about being punished for another raid on the taxpayers' pocketbooks.When the House of Representatives voted against the home care plan this week, it decided not on the bill's merits but because the appropriate committees of Congress - particularly the House Ways and Means Committee - had not held hearings on the measure.

Since the home care bill would involve a major tax increase, the attempt to skirt the main House committees dealing with taxes was highly irresponsible. The next time around, the bill's sponsor - Rep. Claude Pepper of Florida - is going to touch all the bases.

Even so, the bill should be defeated again and again. The country simply can't afford it; even if it could, it would be a mistake to put the federal government into an undertaking that private insurance ought to handle.

Only this week Congress passed, and President Reagan is expected to sign, another health program that constitutes the largest expansion of Medicare since its inception. The new program increases Medicare benefits to ease the cost of catastrophic illnesses.

The government can't pile a costly home care plan on top of the catastrophic illness program and still expect to balance the federal budget by 1993, as required by law.

Unlike the catastrophic illness program - financed entirely by those who stand to benefit from it - the proposed new home care plan would be paid for by all taxpayers. It would be financed by eliminating the $45,000 ceiling on income subject to the 1.4 percent tax dedicated to Medicare.

Since not only the elderly but also chronically ill younger adults and children on respirators or other medical machinery would be eligible, the home care plan would be the first significant expansion of Medicare to those under 65.

But the biggest stumbling block is the program's cost. The price tag supposedly would come to $30 billion over five years, but the cost could easily be much steeper. The Department of Health and Human Services, for example, puts the figure at $63 billion.

Even the higher figure could be too conservative. Why? Because most home health care is now provided by families, free of charge. The Pepper bill would take the fateful step of replacing this admittedly uneven system with a brand new, federally-supported entitlement program. No one can be sure how many people would apply for the program, let alone be considered eligible. Consequently, no one can be sure how much it would cost.

Nor is it known how the home care service would be provided or overseen; as The Washington Post notes, "the necessary professionals don't exist."

The next time the home care plan comes before Congress, the measure should be seen for what it really is - a test not of compassion but of common sense. It's a test that can be passed only if Congress keeps refusing to write what amounts to a blank check.