There was a time when a homeowner who wanted a swimming pool had two options: buy an above-ground pool or dig up the backyard and have a concrete pool poured from scratch. The above-ground pool had limited options for a deck and was not very attractive, while the concrete pool was prohibitively expensive. Enter preformed swimming pools. This option looks exactly like a poured concrete pool, but involves half the construction costs.

Preformed swimming pools are rather like large fiberglass bathtubs. They are formed at the factory, where the maker seals the surface against the elements and ravages of chlorinated water and ships it to the home. The contractor digs a hole, levels it with sand and sinks the pool into the hole. The pool is flush with the top of the ground, so it can be decked and landscaped just like a concrete pool.

One of the greatest advantages of preformed swimming pools is that the contractors may take only 7-10 days to install one, as opposed to a few weeks spent installing a concrete pool. These fiberglass pools are also highly resistant to wind and weather. Fiberglass, unlike concrete, is not prone to splitting or cracking, so these pools are ideal for earthquake-prone areas.

Look in any pool supplies catalog, and you will see containers of pool paint for sale. This paint helps maintain the concrete pool surface, but who wants to paint a swimming pool? A fiberglass pool never needs painting. Maintenance costs for preformed swimming pools are lower in general, and because most use sand filters, the cost of chemicals is lower as well. Preformed swimming pools are more cost-effective in both the long and short-term.

Preformed swimming pools are always kept filled, so that the pressure inside equals the pressure of the earth around it. Consequently, it is not necessary to drain the pool every winter -- again saving money.

One of the drawbacks of preformed swimming pools is the same as for concrete pools: terrain issues. A contractor will charge more to remove rocks from soil and will charge for a retaining wall to keep the ground stable if it is soft and prone to shift. Another drawback is that design choices are limited for preformed swimming pools. A regular concrete pool can be designed to the homeowner's wishes, but he is locked in to a few choices for preformed swimming pools.

Installing a pool is a big investment of time and money for a homeowner. Comparison shopping is a must. However, he may find that a preformed swimming pool is exactly what he's looking for.