DEAR MR. MELTZER: We have planned a 10-trip to the Carribean. I am worried about the water pipes freezing while we are away.

Someone told me that to avoid this, I could turn off the water while we are gone. Will this really work? It seems to easy, somehow.

ANSWER: Simply turning off the water is not enough. Your entire system must be drained. This usually involves blowing the water out of your lines with air at high pressure.

Not only can this be a costly job, but very often it is not effective for pipes located under the floor. I recommend that you keep your heat running at a minimum temperature and not drain your pipes.

However, you should have a neighbor check your house on a daily basis, if possible, to make sure that the heating system does not break down.

DEAR MR. MELTZER: My house has electric heat. When we had the system installed, we were told that the ideal feature was the ability to turn off rooms we were not using. Usually we turn off every room in the house except the one we are sitting in.

When we go from one room to another, we turn off the last one and turn on the new one. We are freezing! The electric company tells us there is nothing wrong with our system.

ANSWER: In order to properly heat your house, the heat should be going at all times. You can turn it down, but not off. The electric heat does not have a sufficient recovery power to heat a room instantaneously. Bear in mind that for even heat you must heat not only the space of the room, but the contents as well.

This includes furniture. If everything in the room is below 40 degrees, it takes a long time to properly heat that area.

DEAR MR. MELTZER: My husband and I are buying a brand new house, and have been given a choice of carpeting or vinyl tile for our hallway. Friends have told us that vinyl tile lasts much longer than carpeting. Which should we get?

ANSWER: Your friends have given you correct information. According to all I've been led to believe, carpeting must be replaced approximately twice as often as vinyl tile. And particularly in the hallway, which gets much wear and tear.

DEAR MR. MELTZER: My father is 81 years old and a touch senile. He has lived on a 50-acre farm which fronts on a main highway for 45 years of his life.

Since he lives alone and is not in the best of health, he has decided to sell the farm. When the word got around, a number of his neighbors came around to see him and offered him what I consider to be unbelievably low prices per acre.

I am my father's only child. My mother died about five years ago. So he does rely on me. However, I am really a city person. In order to be of any help to my father, I need expert advice. How can I determine the fair price for his farm?

ANSWER: The way to determine what the general range of land prices is in the area of your father's farm is to go to the county court house. Someone in the recorder of deeds office will assist you in looking up each land sale made in that neighborhood for the past several years.

In this way, you can determine approximately what the farm is worth. To be more certain, hire a professional appraiser or consulting realtor in that same area. In this way, you will know the typical acreage price.

Bernard C. Meltzer, who does not answer letters personally, is a realtor, engineer and appraiser. His address is suite 615, 1420 Walnut St., Philadelphia 19102.