How to Winterize Your Pool in Minnesota: A Step-by-Step Guide
Learn how to properly close and winterize your inground pool for Minnesota winters. Covers water chemistry, equipment protection, cover installation, and common mistakes to avoid.
Why Proper Winterization Matters in Minnesota
Minnesota winters are among the harshest in the country for pool owners. Temperatures regularly drop below zero, and the ground freezes several feet deep. Improper winterization can lead to cracked plumbing, damaged equipment, and a costly spring opening. After closing thousands of pools over 35 years, we've seen every mistake — and the repair bills that follow. Taking the time to winterize correctly in September or October protects your investment and makes spring opening straightforward.
Step 1: Balance Your Water Chemistry
About a week before closing, test and adjust your water chemistry. Target a pH of 7.2-7.6, alkalinity of 80-120 ppm, and calcium hardness of 200-400 ppm. Add a winterizing algaecide and a stain-prevention product. Properly balanced water prevents staining, scaling, and algae growth under the cover all winter. If you use a salt system like the Pentair units we install, lower the salt level slightly and run the system for 24 hours to distribute the chemicals evenly.
Step 2: Clean the Pool Thoroughly
Vacuum the pool floor, brush the walls and steps, and skim the surface. Clean out the skimmer baskets and pump basket. Any debris left in the pool will decompose over winter and create staining or algae problems in spring. Run your Polaris or Zodiac robotic cleaner for a final deep clean. This is also a good time to clean your Hayward filter — either backwash your sand filter or clean your cartridge filter element.
Step 3: Lower the Water Level
Lower the water level to 4-6 inches below the skimmer opening for mesh covers, or 12-18 inches below for solid covers. This prevents ice from expanding into the skimmer and cracking it. Use your pump or a submersible pump to lower the level. Don't drain the pool completely — the water weight helps hold the pool structure in place against ground pressure from Minnesota's freeze-thaw cycles.
Step 4: Blow Out and Plug the Plumbing Lines
This is the most critical step and where DIY winterization most often goes wrong. Use a shop vac or air compressor to blow all water out of the return lines, skimmer lines, and main drain line. Immediately plug each line with a threaded winter plug or expansion plug. Any water left in underground plumbing will freeze, expand, and crack the pipes — one of the most expensive repairs we see every spring. If you're not confident in this step, our service team handles it as part of our professional closing service.
Step 5: Protect Your Equipment
Remove the drain plugs from your pump, filter, heater, and chlorinator to let any residual water drain. If you have a Hayward SuperPump, remove both the pump drain plug and the strainer pot drain plug. Store the plugs in the pump basket so you can find them in spring. Disconnect the heater's pressure switch to prevent damage. If you have an automatic pool cover by Cover Star or SwimWise, follow the manufacturer's instructions for winter operation — many automatic covers can remain deployed all winter.
Step 6: Install the Winter Cover
Install a quality winter cover secured with water bags or cable and winch. A mesh safety cover is the best option for Minnesota — it lets snow melt drain through while keeping debris out and providing child and pet safety. Solid covers require a cover pump to prevent water accumulation. Make sure the cover fits snugly with no gaps where wind can catch it. Check the cover periodically throughout winter and after major storms.
When to Call a Professional
If you've never winterized a pool, have an automatic cover system, or simply want peace of mind, our professional closing service covers everything: chemistry, cleaning, plumbing blow-out, equipment protection, and cover installation. We've closed pools across the Twin Cities for over 35 years. Call us at (651) 653-6807 to schedule your fall closing — spots fill up fast once September arrives.