Although we all think of water as a natural resource that costs little or nothing and is almost always available, it is evident that stringent conservation is more and more essential to our survival. This can be seen from the current shortages in the mid-Atlantic area, where rainfall has been well below average for months.

Not only is conservation necessary if we are to ensure an adequate supply of water for the future, it is also important to most homeowners as a practical means of cutting energy costs. Much of the water that has been heated with high-cost fuel or electricity. Every drop wasted also wastes the energy that was used to heat it.

But cold water also costs money and this cost must be borne by all taxpayers in one way or another. Some homeowners pay for their water directly through the use of meters, while other pay through special taxes that are included with their property taxes. Even those who rent pay taxes for water and sewage treatment; (water must be disposed of after it is used, so the more the use, the more the system has to take care of.

Fortunately, there are a number of simple and inexpensive steps that can be taken to lower water consumption without lowering the quality of life or the ability to maintain normal standards of health, comfort and cleanliness.

The most direct and obvious way to cut down on water waste is to repair dripping or leaking faucets promptly. Even a small drip can waste up to several gallons per day, and if this drip is in one of the hot-water faucets, the energy costs will add up surprisingly fast. The inexpensive parts needed to make the repairs are available in all hardware stores, and in most cases repairs can be completed in a matter of minutes; (for the inexperienced, easy-to-follow instructions can be found in most how-to books).

In addition to replacing leaking washers promptly, faucets can also be modified to use less water by adding aerators to those spouts that do not already have them -- especially on older fixtures. An aerator cuts down on the volume of water used by as much as 30 to 40 percent, without seeming to cut down on the apparent force of the flow.

One of the biggest water-wasters in the average household is the toilet -- it uses from 6 to 8 gallons for each flush. This can be reduced in several ways, the most popular being to displace some of the water in the tank without lowering the water level when the tank is full; (this would lower the flushing efficiency).

A good way to displace some of the water is to install a dam-like device that can be fitted to the inside of the tank to hold back some of the water during each flush. Less water is required to refill the tank and it refills to its normal level, so flushing efficiency is not impaired.

These devices are generally sold through mail order houses at prices ranging from $4 to $7, but the homeowner can easily make his or her own by cutting off the top of a plastic 1-gallon jug and placing it on the bottom of the tank with a few rocks in the bottom to weigh it down. The jug will fill with water and stay full during each flush without affecting the height of the water inside the tank -- thus using less water for each flush.

With this homemade dam device, as well as with the commercially sold varieties, some experimentation will be required to determine the exact volume of water that can be held back without affecting flushing efficiency (with solid waste in the bowl).

Another way to cut down on the amount of water use for each flush is to install one of the various dual-flush accessories. These make use of the fact that all flush toilets are designed to dispose of solid waste with a single flush, even though this requires more water than disposing of liquid waste. With a duel flush unit, about half the water is used when there is liquid waste in the bowl, while the full tank is used when solid waste is in the bowl.

There are two methods for accomplishing this: One is to add a small weight to the flapper valve or rubber ball at the bottom of the tank to make it shut off the rush of water into the bowl before the tank is fully emptied. The simplest way to add this weight is to place a few large washers, or wrap some pieces of wire solder around the chain or lift rod that raises the rubber ball or valve.

The other way to convert to a dual-flush system is to install a small airbleed device that lets air out of the rubber ball or hallow flapper valve to make it closer more quickly and thus hold back some of the water inside the tank. These dual-flush devices are available by mail order from such companies as the Suvway Co., 1138 Neill Ave., Bronx, N.Y. 10461 ($5.98); and Carlton Industries, 2630 Walnut Dr., Tustin, Calif. 92680 ($7.95).