Most whole-house systems require some plumbing knowledge. If you can handle a wrench and have watched five YouTube videos, you can do it. But if your DIY skills end at assembling IKEA furniture (and then crying), hire a pro. The cost is usually under $300, and it saves you from flooding your basement. Remember: water in the basement is a story, not a happy ending.
For point-of-use systems like under-sink filters, installation is a breeze. Even I did mine in 20 minutes, and I once installed a doorknob backward.
