How To Winterize Your Swimming Pool, Spa or Hot Tub

A basic part of looking after a swimming pool, hot tub or spa is getting prepared for the months when it is out of commission. This time is known as “pool closing” or “closing your pool,” and the most appropriate time to complete this work relates to your region or climate. Pool experts say the right time to close the pool is when the daytime highs are in the region of mid-60s to low-70s, and nighttime drops into the 40s.

Closing the pool too early can lead to issues with algae overgrowth. Also, if you leave if late enough for trees to shed their leaves, this increases the workload with more debris to clean up.

How difficult: Average

Time-frame to complete: Start testing the pool water about 1 week prior. The actual winterizing takes maybe two or three days.

What steps to take?

Why Winterize?

In accordance with the Association of Pool & Spa Professionals (APSP) it is a wise decision to winterize the pool structure, equipment and plumbing to protect against freezing. They also recommended the pool and related equipment gets checked to make sure everything is fully functional. The best course of action is to have the repairs done before closing your pool. Try to complete this work before the first freeze of the season arrives.

Clean the water

Give the swimming pool or hot hub a thorough vacuum to remove all signs of debris. Vacuum to the filter position or up to the waste indicator – whichever is relevant. Also, a portable pump unit is an option.

Water treatment

Balance the water’s total alkalinity, calcium hardness and pH levels. Use the appropriate winterizing chemicals which include treating the water with an algaecide, stabilizer and sanitizer. The winterizing treatment is a must-do step to prevent the water becoming corrosive when the temperature reaches the freezing point or below. Use chemicals before placing the pool cover or before draining. Read the instructions carefully for each chemical before use.

Lower the water level

The pool water levels need to be lowered after the valve on the skimmer line gets closed. The water level should drop in the region of 18 inches from the height of the pool coping. The exact adjustment can vary with the type of pool (see the next point for more info).

Water levels and covers

Let’s take a look at how the water level changes with the different covers:

Plaster finish with solid material cover: Go for a reduction of 2.5 to 15cm / 1 to 6 inches below the tile time or mouth – whatever is lower

Automatic cover: Keep the water equal or above the bottom of the skimmer mouth

Vinyl-Lined: Aim to lower by 2 cm/ 1inch from the skimmer mouth – increase this in regions that experience a lot of snow or heavy rainfall

No cover or mesh cover: Go with 45 to 61 cm / 18 to 24 inches below the skimmer mouth

Natural-Finish or painted with solid material cover: Aim to lower the water 15 cm / 6 inches below the mouth of the skimmer

Hydrostatic pressure: An inground concrete pool fully drained can be destroyed if the necessary precautions are not taken. For instance, leave the drain valves at the bottom open. In most cases it is best to leave the pool full if uncertain.


Clear the piping of all water in line with the manufacturer’s guidelines. Blow water from piping where necessary with an air compressor or a tank vacuum cleaner operating in reverse. Also, clear the filter and heater of all signs of water. Use a non-toxic antifreeze (not the same as a vehicle antifreeze); widely available at any good pool store. The antifreeze is effective at stopping the water from freezing to -12° C / 10° F.


Check that the valves are thoroughly drained. Seal any of the valves below the water level. Any lines below water level are sealable with electric heat tape in areas that cannot get filled with antifreeze or drained.

Pool equipment

Remover diving boards, ladders, handrails, etc. and give a proper clean. Store the pool equipment in a dry, cool place for the winter. Try to store the diving board flat.


Any lights with less than 45cm / 18 inches of water above them get removed. Store the lights in a dry place after wrapping in plastic. Place the lighting at the bottom of the pool if no other suitable storage is available. For extra safety, turn off the circuit breaker or remove the fuse to avoid mistakenly turning on the lights.


Drain the pump by removing the plugs. Alternatively, use a wet/dry shop vac to clear all water from the strainer compartment and housing. Add .12 to .24 liters / ½ to 1 cup of antifreeze to the housing with the drain plugs left in place. Also, put on the pump lid / strainer. For the pumps make in cast-iron, use a suitable lubricant to coat the drain-hole threads to minimize the risk of winter corrosion.


For the pool owner living in a cold climate, you will want to store the pump motor in a dry, warm place. Make sure to remove it carefully and always disconnect the power before attempting to remove.

Circuit Breaker and timer

If the pool has a timer, you want to switch it off after removing the timer lugs. Also, the circuit breaker should get switched off or remove the fuses.


When the pool water starts to lower, use a sand cleaner and backwash up to 5 times longer than normal. However, this shouldn’t take place while vacuuming. Open the air relief and drain cocks, while also removing the drain plug. The multi-port valve should be put in the “winter” position. Leave the air-relief valve open. For other filter types like DE units or cartridge, make sure to check the manual. Once the pump and lines are winterized, the filter should be entirely drained. Also, apply a suitable lubricant to the drain plug threads to avoid corrosion or rusting.


When putting the cover in place make sure it is tight and secure to stop dirt or debris getting into the pool until next spring.

Useful tips

Try to use a test kit to check alkalinity, pH levels, etc. about 7 days before starting the work of winterizing the pool.

  • Supplies need
  • Air compressor
  • Antifreeze: non-toxic and available from a pool store
  • Brushes: algae, tile, floor, wall, etc.
  • Chemicals: winterizing kit, algaecide, stabilizer, sanitizer
  • Plastic for wrapping lights
  • Pool test kit
  • Sand cleaner
  • Toolkit
  • Vacuum (shop vac or tank-style)
  • White grease: heavy grease to avoid corrosion or rusting

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