Well sure! If you have access. But you'll find that chlorine lasts a lot longer in cold water... in your neck of the woods I'd venture to guess you might only need to add something once in a blue moon. Test it about once a month in cold NE weather and treat accordingly. If you add some bleach you will need to be able to mix it up a bit using a broom or something since your equipment is offline. I'm sure it will make opening in the spring a breeze as your water won't have been entirely untouched those months under cover. Maddie

Bostonpool: Adding chlorine in the winter is a great idea as Maddie suggested, if you have the ability to mix it. Given the weather moving forward, IMHO, I feel the potential problem may exist if you open up late in 2018. Depending on where you left off, the FC levels will hang around for a while. It is recommended that you open at least one month before memorial day as this will help. Even if you have a small problem, cleaning up will not take long, in the early spring. EDIT: Worcester, MA is a nice area. My first company, outside Prudential was located in town. The State Mutual Companies, who later changed the name to Allmerica Financial. Eventually they shut down in 2004.