LONDONDERRY — In between swatting mosquitoes in the stagnant July heat, Mark Jacobson heaved an audible sigh of relief as the deliverymen this week installed his sparkling new hot tub.

Relief that he and his family would have a bubbling respite from the summer swelter.

Relief that after being one of 11 residents who bought spas at a home show in Manchester last April, someone was finally making good on a promise.

“That’s a lot of hard-earned money there,” Jacobson said, as he, his wife and his two boys dipped their hands in the warm, bubbling water. “That’s money we saved by working, by not spending extravagantly, by not going on vacations.”

Thanks to the spa manufacturer, Jacobson and 10 others are getting delivery of spas totaling more than $40,000 in value. But the New Hampshire Attorney General’s Office late last week confirmed in a letter they’ve launched an investigation into the business practices of the man who sold the spas, All Clear Pool and Spa owner Ray Donahue Jr.

“What we look at is the number of consumer complaints that have come in, whether the dollar amount is adding up and whether the business owner has gotten back in touch with us,” said Connie Stratton, an assistant attorney general in the state’s consumer protection bureau.

State justice department officials indicate Donahue, of Hooksett, failed to appear last month for questioning after being issued a subpoena from their office. By that point, Stratton indicates her office had registered 17 consumer complaints about All Clear or Hooksett Pool and Spa. A check with the state’s Better Business Bureau revealed Donahue’s standing to be “unsatisfactory” due to “a pattern of no response to customer complaints.”

Attempts to reach Donahue this week were unsuccessful — business, home and cellular telephone numbers given for him either rang unanswered or had been disconnected.

“It’s been a major headache, quite honestly,” said David Livingston, owner of Williamsport, Penn.,-based PDC Spas. The manufacturer of the spas being sold by Donahue at the home show, PDC (short for Plastic Development Company) spent this week in damage control mode, delivering spas to customers like Jacobson; spas for which Livingston says he never received payment from All Clear.

“We spent the better part of three weeks dealing with customers over this issue,” Livingston said. “The problem with this, of course, is that we’re in manufacturing, not retailing. We didn’t have to do this. But I think this left a bad taste in a lot of people’s mouths when it came to purchasing spas, and I hate to see that. It’s also a pretty small industry, and this is not the kind of publicity a company needs.”

For Jacobson and his wife Lisa, the 26-jet Dynasty model five-seater in “Galaxy green” was supposed to be their fifth wedding anniversary gift to each other. When the two attended the home show at Manchester’s Verizon Wireless Arena on April 13, it didn’t take them long to pick out the spa they wanted — or the dealer they wanted to visit.

“We saw probably about three or four vendors there, but Mr. Donahue’s was the only booth that had the spa we were looking for actually up and running with water going through it,” said Jacobson, a 42-year-old salesman for Amerigas.

Before long, the couple had signed a contract and enthusiastically plunked down the full $4,347 by check, with visions of relaxing after-work soaks and weekend at-home getaways.

When Jacobson didn’t hear from Donahue for the next two weeks, he said he began to get nervous. Donahue, he indicated, was supposed to call him and recommend a company to install a concrete pad for the spa.

“I had to go through several phone numbers, including his father’s, just to reach him, and when I finally did, it was like he was putting me off,” said Jacobson, who said he left unanswered messages for the next month trying to confirm a delivery date.

“When I finally reached him again, and figured something was wrong, I asked for my money back,” Jacobson said. “That’s when he said he didn’t have time to talk to me.”

That’s also when Jacobson says he called PDC, which had placed representatives in Donahue’s booth at the home show. The news wasn’t good.

“We called PDC and they told us up front that Mr. Donahue hadn’t paid for the tubs anyone had ordered,” Jacobson said. “That was a big ‘Uh, oh!’”

For the next three months, Jacobson launched a letter-writing campaign, contacting the attorney general’s office, the Better Business Bureau, the local news media — anyone, he hoped, that could look into his claim.

When authorities in Londonderry and Hooksett informed Jacobson his case wasn’t a police matter, he filed an immediate claim in Concord with the justice department’s consumer fraud division.

Jacobson’s main problem, says one expert in consumer fraud: he’d paid cash in full for his hot tub, sight unseen.

“If you pay in advance for something to be delivered later and that person is not from a major corporation or reputable entity, you’re in really risky business,” said John Sheldon, staff attorney with the National Consumer Law Center in Boston. “Don’t pre-pay for anything, until you see it and are satisfied with it.

“The best advice I can give is to tell the seller, ‘When you deliver it, I’ll give you the check,’” he continued. “That’s your power as a consumer, and it’s the main way to deal with fraud. If things fall through, your only recourse at that point is to try to find a third party to whom you can attach some responsibility — either as a partner with the agent that ripped you off or to appeal to that party’s goodwill.”

That party was PDC.

Though Livingston argues he wasn’t obligated to deliver goods he was never paid for, he says his decision was as much about goodwill as it was about preserving the good name of the company his father started in 1957.

In all, Livingston’s company delivered five spas this week to residents who’d attended the Verizon Home Show and paid cash. Most of the people who’d paid Donahue had done so by credit card and were able to get out with minimal damage. As for PDC’s bottom line, Livingston estimates Donahue cost his company roughly $20,000 through the spas he delivered this week.

“I could pursue this legally, but the fact is, we’re providing these spas to these people by choice, not because we have to,” Livingston said. “Plus, even if we did catch up with Mr. Donahue, you know the old saying, ‘You aren’t going to get blood out of a stone.’”

As for Jacobson, he arrived home Tuesday from work to find deliverymen from PDC, including Livingston’s own son, installing his “Galaxy green” five-seater in his backyard. As his kids looked on excitedly, Jacobson’s face registered a mixture of relief and fatigue.

“I didn’t believe it was actually going to be here and that there would be a happy ending,” Jacobson said. “With all the bad news we’re hearing about corporate America, it’s a good feeling to know someone is standing by his company’s name. I’d also like to think my persistence played a role."