It can be left in the pool but it is not advised in terms of longevity. The cleaner will last longer if it is removed and hosed off after use. You have to pull it out to clean out the filter basket and so it best to just take it in and out. The controller has a feature where you can leave it in the pool and have the unit run every day, every other day or every third day. So if you were going to be on vacation you could dump it in the pool and go.