There is a simple answer to this question and a more in depth one. The short answer is that most financing sources that are truly competitive in swimming pool financing (as opposed to banks, mortgage companies, local credit unions, etc.) offer terms up to 20-25 years. Those loans will usually be the lowest payment and a popular option.
The slightly more complicated answer relates to what type of loan you should opt for based on your financial situation. Longer term loans almost always come with higher rates. Lenders charge a premium to tie up their money for so long. Also, the longer you stretch the term, the more interest you pay over time. It’s important to speak to a qualified loan consultant to see what’s right for you. For instance, if you don’t mind a slightly higher payment, say $100 per month, that would come with a shorter term and a lower rate. When you do the math, that extra $100 you pay every month will allow you to pay thousands less in interest over the life of the loan and pay the loan off sooner. It’s important to find the “sweet spot” where you’re comfortable with the payment but are still able to take advantage of the shortest term and lowest rate.
There is no “one size fits all” option so it’s very important, especially on a project with this level of importance, to speak to an expert and know all of your options. Small changes in term and rate can save you or cost you a lot over the life of the loan.