AboveGround Pools: A Buyer’s Manual

THE nice thing about an above-ground pool is that the biggest decision is how large the pool will be, right?

Well, not really.

"Installing any pool of any size is a complex undertaking," said Bill Weber, the president of the Association of Pool & Spa Professionals in Alexandria, Va.

In addition to the size, other factors that must be considered are the shape and structure of the pool; the type, thickness and style of the liner; the kind of filter and filter pump; and the suitability of the space where the pool will be located.

Rob Coxworth, the owner of Webfoot Leisure, a pool company in Nashville, said above-ground pools range in size and shape from a 12-foot round to an oval 21 feet wide and 41 feet long. Costs range from 0 "to as much ,000, not including installation," he said.

There are two types of liners. With the overlap type, the vinyl liner is draped over the vertical pool wall and then held in place by top rails. With the more expensive beaded liner, there is a thickened preformed fold along the edge of the liner that is pressed into place on the pool wall.

The liners also come in different thicknesses, styles and colors, with thicker, more ornate liners costing more than standard "basic blue."

The right pool site is critical. "You need a nearby source of power to run the pump," Mr. Coxworth said, "and you don't want to install under trees, power lines or telephone lines. The bigger the pool, the bigger the area that has to be leveled and cleared."

Above-ground pools are typically installed on a firm bed of sand, and the cost of site preparation can range from a few hundred dollars to ,000 or more.

Round pools are usually buttress-free, and oval pools can be either buttressed or buttress-free. Beverly Roberts, who owns DefinitivePools.com, an Internet retailer based in Nashville, said that those with buttressed walls have diagonal bracing along the sides to counteract the pressure of the water.

Buttress-free pools are engineered to withstand that pressure without diagonal supports. "The bottom line is that you can put a buttress-free pool in a smaller space because you don't need the extra three feet on each side for the supports," she said.

Deciding on the proper filter and filter pump is also important. Ms. Roberts said there are three filter types: sand, cartridge and diatomaceous earth - D.E. for short.

A sand filter, she said, will trap particles down to a microscopic 20 microns in size. (The diameter of a human hair is 75 to 100 microns.) A cartridge filter will trap particles down to 10 microns, and a D.E. filter down to 3 or 4 microns.

Sand filters are the most common type sold in above-ground pool packages, she said, and people who want the enhanced filtering power of cartridge or D.E. filters will pay extra. "For most people, a sand filter will do the job," she said.

The filter pump will usually run on standard 110-volt household electricity, but higher-powered pumps may need a 220-volt circuit. Either way, it is important to provide a safe source of power. "You have to check with your local code enforcement people to find out what is required," Ms. Roberts said.

Mr. Weber of the pool and spa association said that just as important as choosing the right pool is choosing the right installer. "Most pool installers are subcontractors," he said. "You want to make sure that the installer is licensed, insured, has a good reputation and is familiar with the kind of pool you are installing. You want to meet the installer in person, get references and satisfy yourself that he knows what he's doing."

Installation costs vary. Pat Zech, owner of Yorktown Pools & Spas in York, Pa., said that a small round pool can be installed for about 0; a large oval could cost ,000 or more.