One quick way is to do a Google Search like "pool maintenance services in Your City" This will show you your potential competitors. Check their websites and social media to understand their services and pricing. Also in many ways if there are several with multiple reviews and full Google Business profiles, that means it is a viable business in yourr area. I would not be worried about competition in terms of how "many". It makes more sense to see what the successful ones are doing to be successful, then do the same and then add something that makes you stand out.
One quick way is to do a Google Search like "pool maintenance services in Your City" This will show you your potential competitors. Check their websites and social media to understand their services and pricing. Also in many ways if there are several with multiple reviews and full Google Business profiles, that means it is a viable business in yourr area. I would not be worried about competition in terms of how "many". It makes more sense to see what the successful ones are doing to be successful, then do the same and then add something that makes you stand out.