“We were sitting around a campfire in 2005,” recalled Michael Hawkins, owner of San Diego Hot Tub Rentals (858-578-8822, sandiegohottubrentals.com), “and we saw an inflatable hot tub in a Popular Science magazine. We thought, That would be great to have when we got back from going out downtown. And then we thought, I bet someone would want to rent it from us.”

He was right. Today, Hawkins said, “We do vacation rentals along the boardwalk, we’ve been down on the beach, and we’ve been on rooftop decks. And I have a portable battery pack, so we can set up a hot-tub party trailer. It’s about 20 feet long, and a little more than a third of it is an elevated floor for the hot tub. You can have people standing on the back by the barbecue and the Kegerator, and there’s a bar rail along the whole thing.... Once, we did a Super Bowl hot-tub party at the Leo Carrillo campground in Malibu. We had DirecTV’s NFL Sunday Ticket set up with a flat-screen right there at the campsite.”

By the time he made it to Malibu, Hawkins had found a better product than his original inflatable model. “Now, we use Softub hot tubs. They’re made from high-density foam and covered in marine-grade vinyl. Some of the blow-up or assembled hot tubs will only have champagne-style bubbles coming up; they won’t have jets like you’d find in a Jacuzzi. But the Softub has those Jacuzzi-style jets.... All you need is the outlet, a water source, and a level surface.”

Hawkins ran down the rest of the specs. “The ones we rent are the largest model: room for six people, 300-gallon capacity. But because they’re only 75 pounds, you can flip them on their sides and roll them through a standard doorway. We bring a continuous hot-water heater that runs on propane; if the heat drops a couple of degrees while you’re using it, the heater will turn on and keep the temperature maintained. For safety, there’s a locking lid. We use a very small dose of granulated chlorine — usually about three days’ worth. And there’s a device inside the motor pack that pushes out ozone, and that acts as a sanitizer to kill a lot of the bacteria. That way, you use less chemicals. Unless there’s heavy use with a lot of tanning lotion or things like that, it usually stays pretty clean for a weekend. But we teach you how to use it and give you enough chemicals for whatever rental period you need.” A rental costs $349 for a Friday-to-Monday weekend; $299 daily for midweek. The party trailer is $499 daily. Summer and Christmas are the busiest times of year; call to reserve.

“We come and drain it,” continued Hawkins. “We try to reclaim as much [water] as possible. As long as you don’t put additional chemicals in, the water becomes neutral within 24 hours, and so it’s safe for plants or lawns. I actually partnered with a mobile car detailer; he sometimes uses it for rinse-water.” He has also partnered with massage therapists to provide day-long retreats. “We’ll come in with tables. Five one-hour massages plus a hot-tub rental would be $750.”

Like Hawkins, Ed Vasquez at Hollywood Hot Rub Rentals (619-312-2592, hollywoodhottubrentals.com) also has a varied client list. “I never ask what people are doing. I had an auto mechanic put one in his shop. And I’ve done three or four baptismal setups at churches. I’ve never had a bad customer, though the college guys at San Diego State are hard on them. We have a pretty extensive contract; the renter has complete liability for everything from uninvited guests to uninvited pets.”

Also like Hawkins, Vasquez rents Softubs, but he carries the two- and four-person hot tubs as well as the six-person. “The two- and six-person tubs are the most popular. The six-person comes with a little bench seat and a spa light. But you don’t really need the bench; when you sit in them, you’re kind of buoyant. You’re just floating.”

Vasquez found that “most people rent them for only a day or two, so they’re fine without doing much in the way of maintenance. But I do have people down by the beach who will keep it for a week or two, and then I have to clean it once or twice a week. I’ll pump out the water, hose it down, wipe it with chlorine, and then fill it back up.”