A "pool route" is a portfolio of recurring residential or commercial swimming pool service accounts that one operator services on a weekly schedule.
The asset isn't the truck, the chemicals, or even the customers individually. The asset is the recurring billing relationship and the route density that makes it efficient to service them.
A typical residential account pays $150-$200/month for weekly service: chlorine check, brush, vacuum, filter clean, equipment inspection. Multiply that across 60-150 stops on a tight geography and you have a small business doing $10k-$25k/month in fairly predictable revenue.
That predictability is why routes sell for a multiple of monthly billing — usually 8-14x monthly recurring revenue, depending on density, account quality, and how the books look.