The kidney-shaped swimming pool trimmed with tile is the equivalent of orange shag carpet — once au courant, now tragically out of date.

Today, fashionable swimming pools are sleek and rectangular or lagoonlike with boulders and waterfalls. Many have “green features,” such as mineral purification and solar covers.

Others are so upstaged by lush landscaping, outdoor kitchens and even putting greens, says Don Gwiz, principal of Fairfax County-based Lewis Aquatech, that “you might think, ‘Oh, there’s a pool, too.’”

“It’s more about the architecture and the floor plan,” says Gwiz, who specializes in high-end pools.

Given that a standard model can cost as much as $150,000, a pool is about as practical as a sports car. Still, experts say it’s important to be pragmatic about this luxury. In considering a pool, homeowners should ask themselves: How much will it cost, and how long will it take to install? What’s the permitting process like in my community? How much will it cost in time and money to maintain?

“It might be different for a typical family who just wants to get the kids wet and a couple in retirement,” says Chuck Browning, head of construction at Germantown-based Browning Pools. He says the homeowner’s priorities will determine what kind of materials are used and the layout.

A large, shallow area — sometimes called a “sun shelf” or a “kids’ zone,” depending on the client — is showing up in many pools, Browning says. The wading area (which can be a level 18 inches or slope to three feet) is even an option in vinyl-lined pools.

Rectangular pools remain a classic choice, he says. In addition to providing a timeless look, automatic covers can be installed, which reduces the maintenance requirements. A solar cover also helps heat the pool, Browning says.

The free-form pool is among the most popular options, especially on the high end. “It looks like it was meant to be there,” says Don Nesmith, a landscape architect and president of Gainesville-based Land and Water Design.

Boulders, hills stone paths and waterfalls can create an organic look. Pebblelike textures, which can be applied in a range of colors, on the bottom and sides of the pool add to the illusion of being natural.

Ron and Lynne Bergman opted for the free-form look when they had a pool installed in their backyard in Potomac.

“We wanted it to feel like a resort,” Lynne Bergman says. “No matter where you stand, the view is gorgeous.”

In addition to their free-form saltwater pool, the couple has a putting green, an outdoor kitchen and fire pit, and a cabana.

No matter the shape, about 75 percent of the pools installed by Browning Pools have some kind of water feature.

Waterfalls are the most popular, Browning says. There are two kinds: the type that makes water churn and foam as it descends and the type that sends water in “sheets” over a sheer drop.

There are also fountain jets, arcs and various other cascades, many of them highlighted by LED lighting fixtures.

“I think a lot of people like [the water features] because they drown out adjacent sounds, such as traffic,” Nesmith says. “They have also become a focal point for landscape designs.”

Landscaping is a big part of any pool project. It’s no longer optional; it’s required.

Municipal officials examine pool landscaping to determine whether it absorbs enough rainwater to compensate for the impervious surfaces. They might require a rain garden, for example, Nesmith says. “It all relates to the Chesapeake Bay,” he says.

The rules and the amount of time it takes to obtain a permit vary widely from jurisdiction to jurisdiction. For instance, the permitting process takes about two weeks in Montgomery County, where building, sediment control and public right-of-way permits are required.

But in Fairfax, it can take more than five months. Grading and conservation plans are required to obtain a building permit, which must be obtained before electrical and other permits may be issued. Depending on the type of soil in the backyard, some pools must be designed by an engineer and inspected by a county-approved licensed professional.

Meanwhile, in Howard County, it’s possible to receive a permit for an in-ground residential pool in one day.

All local governments in the Washington area will require a fence, according to pool construction companies.

Anyone considering a pool should calculate the costs of maintenance.

For many, a robotic cleaner helps with the job of keeping the pool debris-free. Connected to a garden hose or other water source, the device runs along the surface of the pool, collecting leaves, bugs and dirt. It’s popular, in part, because if it stops working, Browning says, “you go to the store and get another one for a few hundred bucks. You’re back in business the same day.”

Another option — popular out West in places such as Arizona — is an in-floor cleaning system. Small jets are built into the floor of the pool. They pop up and push water to a collection point, where the dirt and grime are suctioned away.

Because the systems involve underground plumbing and because Washington winters can get cold, Browning recommends that a professional team close pools with in-floor cleaning at the end of the swimming season, so that the underground pipes don’t freeze and break.

Bergman, who grew up with a pool, says he remembers the old days of chlorine, brushing, skimming and vacuuming. “It’s come a long way,” she says.

Almost all of Nesmith’s clients at Land and Water Design want saltwater pools. They are friendlier to the environment, relying more on saline than chlorine, although some chlorine is still used to kill bacteria, he says.

“They’re softer to the skin,” Nesmith says of saltwater pools. “People don’t like the smell of chlorine.”

Europeans use far more ozone generators and mineral purification systems to help clean their pools, but Americans are catching up, Browning says. Although the systems are more costly, he says, “they require less chlorine, which, let’s face it, isn’t good for the environment. It kills plants.”

Both saltwater and chlorine pools require regular checks to make sure the water chemistry is correct. But in general, experts say, chlorine pools require more maintenance to keep the pH and chemical levels in check. The additives also cost about $50 a month. Additives for saltwater pools are about half that, on average, but the initial treatment costs several thousands dollars.

Heat pumps and electricity-saving variable-speed pumps also trim energy costs, Browning says.

Hot tubs, or spas, have long been an alternative to swimming pools, and manufacturers have made them friendlier to the environment with features such as low-amp pumps and foam insulation to save energy and silver-ion mineral cartridges and ozone generators to reduce chlorination, says Dave Cintorino, president of Reston-based Home Escapes.

The decks, now made of longer-lasting synthetic wood, can be customized to give an “in-ground” look. Interiors that typically had a faux-marble appearance are usually done in solid colors. “Espresso and java are big colors now,” Cintorino says.

In addition to being more efficient, the spas are more comfortable, he says. And like pools, almost all of them have some kind of waterfall. Accompanying sound systems are often built-in and include digitally controlled LED lights.

Another choice is a swim spa, which can cut the cost of buying a pool in half. Jets propel the water, making it possible to swim in place, Browning says. “It still gives you water therapy in a smaller space,” he says.

Small doesn’t necessarily mean inexpensive, though. There are clients in the Washington area with small backyards and very small, very expensive pools. “They’re cocktail pools,” Browning says.

They can cost several hundred thousand dollars. Options include water features, pebblelike finishes, stone patios and very lush landscaping. They’re for soaking and lounging — like having a cocktail, think sipping, not gulping.

At the opposite end of the price spectrum are splash pads. You’ve seen them in water parks — patio areas with jets of water arching up and kids having the time of their lives.

Splash pads have been popular for a while in water parks and in backyards in the Midwest and Southern California, but they are a new option for the residential market in the Washington area.

The concept is simple, says Bill Stanley, owner of Cedar Creek Run Construction in Culpeper. “The patios have a buried 500- to 1,000-gallon cistern,” he says. “The water is pumped up through the jets and then drains to a central point to be recirculated.”

The systems cost about $10,000 to $15,000. And like pools, they require chlorine. But they are safer — and, therefore, especially appealing to families with young children — because there is no standing water.

Fences aren’t required either. And the patio area — covered with a non-slip rubber material — can be used for other purposes when the spray jets aren’t on.

There are dozens of spray and patio configurations, says Stanley, whose company is one of the few in the area that install residential splash pads. “You can get crazy with them.”

Don’t be surprised if a simple pool or spa project turns into something more.

David Miller, a consultant in Vienna can attest to this. His patio needed to be replaced. He now has a screened porch, a fire pit and a seven-person hot tub — in addition to a new deck. “We have a swimming pool, but you don’t use it in the winter. The hot tub is relaxing,” Miller says. “You get in for 30 minutes before bed, and you sleep like a baby.”

It’s also a visually stunning addition to the backyard. It’s partially sunken, with a stone wall on three sides and waterfall, exemplifying trends in pools and spas.

“Before, the backyard didn’t have an ‘Oh, wow’ factor,” Miller says. “It does now.”

Laura Barnhardt Cech is a freelance writer.