Use all three in your neighborhood, and adjust for the pool. Use a couple out of the neighborhood, in a similar area, with pools to support the adjustment. Then 'splain what you did, and why you did it, so the under writer knows what you're thinking. "Sales 1 to 3 are the best and most similar sales in the neighborhood, but require a large adjustment as they lack a pool. Sales 4 and 5 are not in the subject's neighborhood, but are in a similar and competing neighborhood. They are the only recent and similar sales of homes with a pool." (if it sounds redundant, they like that

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When dealing with a situation like this, using only 3 comps is not going to cut it. You will need to use 4, 5, or 6 comps. Then explain what you did in an addendum.
It's not really hard, but over time you will learn what an under writer is looking for to support the adjustments. Bracket the comps as best you can.
:idea: P.S. If the comps with a pool are in a superior neighborhood, don't forget to adjust for location. Then your comment would be more like: "Sales 1 to 3 are the best and most similar sales in the neighborhood, but require a large adjustment as they lack a pool. Sales 4 and 5 are not in the subject's neighborhood. But are the only recent sales available of homes with a pool. These sales are in a superior neighborhood, so a location adjustment is necessary."
I need to uze my speal kech.