How to Winterize Your Swimming Pool, Spa or Hot Tub

Pool Care and Maintenance

woman cleaning pool
Casey Goodlett / Flickr / CC by SA 2.0  

Part of maintaining a swimming pool, spa or hot tub includes preparing it for those months when you won’t be using it. Also referred to as “closing your pool,” or “pool closing,” the time to tackle this task varies, depending on the climate or region in which you live. Most experts believe that pools should be closed for the season when nighttime temperatures are in the 40s and daytime highs are in the mid 60s to low 70s. If you close it too soon, you risk the possibility of algae overgrowth. If you wait until trees really start to shed their leaves, obviously you’ve got a big mess to contend with.

Difficulty: Average

Time Required: One week prior, start testing water. Winterizing may take a few days.

Tip: If possible, use your test kit to check pH levels, alkalinity, etc. about one week before you plan to do the heavy-duty winterizing work.

Why Do You Need to Close Up Your Pool?

According to the Association of Pool & Spa Professionals, it's necessary to winterize the plumbing, equipment, and pool structure before any or all of these components freeze. The APSP advises pool owners to thoroughly inspect the pool or spa structure and all equipment to ensure everything is in working order. If something needs to be repaired, ideally you should do it (or have it done) before closing your pool for the season, if there's enough time before the first freeze

Supplies and Materials

  • Air compressor
  • Vacuum: tank-style, aka shop vac
  • Brushes: wall and floor, tile, algae, etc.
  • Pool test kit
  • Chemicals: sanitizer, stabilizer, algaecide or winterizing kit
  • Nontoxic antifreeze from a pool supply store
  • Toolkit
  • White grease, a heavy lubricant to prevent rusting and corrosion
  • Sand cleaner
  • Plastic to wrap lights

How to Winterize Your Pool and Hot Tub

  1. Clean Water: Thoroughly vacuum your pool or spa and vacuum wastewater to the appropriate location. If your pool filter doesn't have a "waste" indicator, vacuum on the "filter" position only. When applicable, use a portable pump to vacuum directly to waste. 
  2. Water Treatment: Balance the water's pH, calcium hardness and total alkalinity. Chemically treat the water with a sanitizer, stabilizer and algaecide or treat with the recommended amount of winterizing chemicals. Why do you need winterizing treatment? So that the water doesn't become corrosive when the temperature drops to the freezing point or below. Winterizing chemicals will be added either before draining or prior to placing the pool cover. Again, check the instructions that come with your chemicals or cover.
  3. Lower Water Level: After closing the valve on the skimmer line, you should lower the water level to about 18 inches below the pool's coping. How far you lower the level depends on your type of pool. Step 4 suggests water levels according to different types of pool covers. To be certain, check the instructions or website of your pool cover manufacturer.
  4. Covers and Water Levels:
    1. ​Vinyl-Lined: Lower 1 inch / 2 cm below the skimmer mouth, but more in regions that get heavy rain or snow.
    2. Plaster Finish with Solid Material Cover: Lower 1 to 6 inches / 2.5 to 15 cm below the mouth or tile line, whichever is lower.
    3. Painted or Natural-Finish with Solid Material Cover: Lower 6 inches / 15 cm below skimmer mouth.
    4. Mesh Cover or No Cover: Lower 18 to 24 inches / 45 to 61 cm below skimmer mouth.
    5. Automatic Cover: The water level should not be lower than the bottom of the skimmer mouth. 
    6. Hydrostatic Pressure: This can destroy a drained, inground concrete pool if the right precautions aren’t taken (leaving the bottom drain valves open). If uncertain, it's better for your pool if you leave it almost full of water rather than draining it.
  5. Piping: Drain the water and blow water out of all piping, per the manufacturer’s instructions. To blow water out of circulation lines, use a tank vacuum cleaner on reverse flow or an air compressor. Also, try to drain as much water as possible from the heater and filter. Add non-toxic antifreeze – which is different than automotive antifreeze – and is available at most pool supply stores. This solution should protect water from freezing to 10F / -12C.
  6. Valves: Thoroughly drain valves, making sure that any valves below water level are sealed securely. Use an electric heat tape for lines below water level that could be exposed to freezing but can’t be drained or filled with antifreeze.
  7. Accessories and Equipment: Remove and clean all handrails, ladders and diving boards. Try to store in a cool, dry place and store diving boards flat, if possible.
  8. Lighting: Remove lights if they have less than 18 inches / 45 cm of water above them. Wrap them in plastic and store them in a dry place. If you absolutely have no storage room, put weights on the plastic-wrapped lights and place them at the bottom of the pool. To be on the safe side, remove the fuse or turn off the circuit breaker so lights can’t be turned on accidentally.
  9. Pump: Now it’s time to drain the pump by removing the plugs. Another popular method is to get out your handy wet/dry shop vac to remove all water from the pump housing and strainer compartment. Add 1/2 to 1 cup / .12 to .24 liters of the pool antifreeze solution to the pump housing without removing the drain plugs. Don’t forget to put on the strainer/pump lid. For cast-iron pumps, coat all drain-hole threads with a suitable lubricant (ask your pool dealer) to prevent winter corrosion.
  10. Motor: If you live in a cold, northern climate, you’ll want to remove the motor from the pump housing and store it in a warm, dry place. Don’t forget to disconnect the power that leads to the motor before removal.
  11. Timer and Circuit Breaker: If you have one, remove the timer lugs and set to “off.” Also turn off the circuit breaker or remove the fuses from the pool circuit.
  12. Filters: Using a sand cleaner as the pool water is lowered, backwash the sand filters 3 to 5 times longer than usual, but not while vacuuming. Remove the drain plug and open drain cocks along with the air relief on top of the filter. Position the multi-port valve to "winter." The air-relief valve should be left open. For other types of filters – like cartridge or DE units – check the manufacturer's instructions. After winterizing the lines and pump, all filters should be completely drained. Drain plugs should be left out, but apply a strong lubricant to the threads to prevent rusting or corrosion.
  13. Cover: Last but not least is the all-important cover, which should be secured tightly to keep out debris and protect what lies beneath until spring.