Ask Mr. Smarty Plants

Most arborists would say that 8 feet is too close to your pool.  But I have not read of any case of damage to pools or house foundations by catalpa roots.  However, both the Catalpa speciosa (Northern catalpa), which I expect you have, or the Catalpa bignonioides (Southern catalpa) have extensive root systems.  My biggest cause for concern is whether your pool may have a hairline crack, leading to a slow seepage of water in the direction of the tree.  Tree roots tend to grow strongly in the direction of any water source.  So the first step is to inspect the pool for possible leaks.

I would suggest that at the time that you trim branches off in the fall you also dig a trench parallel to and about two feet from the end of the pool.  Trim off cleanly any tree roots that are growing towards the pool and bury some kind of root deflector to prevent roots from growing past that point.  These deflectors, or root barriers, can be found advertized on the Internet.  I have myself found this particular product to be sturdy.  Few large roots would grow towards the pool at a depth exceeding eighteen inches, so your deflector should extend to two feet below the surface.  To further reduce the chances of root problems, restrict any hand watering of the tree to the side away from the pool.

You are already aware of the positive and negative attributes of Catalpa trees. Trimming off the branches does prevent the dropping of seed pods during the winter.  With care you should be able continue growing your tree without harm to the pool.