Swimming Pool Blog

The Dormant Pool - A Winter Check-Up

The Dormant Swimming Pool: A Winter Pool Checklist
 by Sean Griffin, October 30, 2018

The Dormant Swimming Pool: A Winter Checklist

frozen winter swimming pool

The goal of every pool owner is to limit - if not eliminate - the maintenance involved in running and caring for a pool while still enjoying the benefits. Unfortunately, even when your pool is closed for the winter, maintenance may still be necessary to prevent structural damage and expensive repairs. Especially for those living farther north, it is important to take a moment and go through a brief winter checklist before Mother Nature turns your leisurely swimming pool into a makeshift hockey rink.


The water level is dropped when winterizing a swimming pool. The appropriate level depends on the type of pool structure and the type of winterizing cover used. For example, with safety covers, you can sometimes void a warranty by lowering the water more than 18 inches from the top ledge. Although the covers are securely strapped in place, most covers are still designed to be supported by the pool water beneath. Before a deep freeze sets in, peel back a corner of your cover and check that the water level has not dropped or risen too much. A small pump or a siphon can assist you in re-lowering the water below any skimmer mouth or tile line. Also take into account water displacement. A large mound of snow on the cover will raise the surrounding water level. After adjusting the water level you should take the opportunity to add more algaecide or refill your winter chemical floater to help maintain good water chemistry.


The majority of pool skimmers have lids that are not water-tight, and they will accumulate rainwater and runoff. Once you’ve lowered the water in the pool, make sure all the skimmers are plugged and have an expansion device present, which will alleviate any outward expansion pressure from freezing water. Gizzmos are the most common, which serve as both a skimmer plug and expansion device all in one. You can also use a quart or gallon bottle partially filled with pebbles or antifreeze.

Properly winterized pool equipment requires virtually no maintenance, but it doesn’t hurt to do a quick walk-through. Look for warning signs that freeze damage may occur or that it has already occured. Check to make sure there is no moisture at the equipment pad - this will tell you that the lines are properly capped off and all equipment has been properly drained. Freezing is not the only thing to monitor at the equipment pad, however. When the temperature begins to drop, many small rodents and other creatures sometimes make a home out of you filter or heater. I’ve seen filter grids turn into a rats nest and heater firebrick turned into an insulated dwelling for field mice. Not only are these animals a nuisance, but they also tend to chew through wiring and expensive components. If you do not already have a heater cover, I recommend using one in conjunction with moth balls, to ward off unwanted visitors. Usually when I winterize and drain a filter, I only insert the drain plug a quarter turn so that trapped moisture can still escape, but no pesky critters can enter.


Now that you’ve done a quick walk-through to check the water level and the equipment pad, make sure to tend to whatever pool cover you are using over the winter season. If you use an automatic cover pump, test it periodically to make sure it's still working. Most on the market are automatic, but make sure they are receiving power and haven't tripped a breaker. Also ensure the pump impeller has not become clogged and it still has the ability to pump out standing water.

For those who using a solid, tarp-style winter cover, make sure the cover does not become damaged. With holes in a pool cover, you may end up pumping out some pool water with your cover pump - not good! If your cover does have holes, try to patch them or position them closer to the pool edge, and place your cover pump on the opposite side of the pool cover.

Regardless of which type of cover you use, make sure to keep all standing debris off of it. A clean and dry pool cover will last much longer. Clean it carefully with your pool brush and leaf rake, or use a soft push broom. Be careful that sticks on the cover don't snag and puncture it while you're cleaning. Ice on the pool cover should be allowed to melt on its own. Never try to remove ice from your pool cover or thaw it using some wacky method. If a crust of ice is on top, you can carefully poke through to set a pump or siphon, but be careful not to quickly pump out too much water from beneath an ice sheet - it can slip or fall and damage an old or thin pool cover. 

Solid Winter Cover w/ Cable and Winch (Above Ground Pool):

  • Ensure winch system or tie downs are secure. Replace any missing or damaged cover clips.
  • All air pillows should be inflated and positioned properly.
  • All standing water is being removed from the cover (siphon or pump).
  • Monitor water level of pool ensuring no leak has started.
  • Remove leaves and monitor water chemistry.

Solid Winter Cover w/ Water Bags (Inground Pool):

  • Ensure all water tubes, Aqua Bloks or other water weights are sufficient in weighing down perimeter of cover. Replace any compromised water tubes or bags.
  • Ensure pump is working and has not become clogged.
  • Monitor water level to ensure pool water is not being removed from the pool. Patch any holes or tears that appear on the cover.
  • Remove leaves/monitor water chemistry.

Mesh Pool Cover (Inground or Above Ground Pool):

  • Mesh covers have come a long way in reducing the amount of sunlight and debris that pass through to the water. Make sure the mesh material is always allowing water to drain properly.
  • For safety covers, check that all straps are securely anchored with the springs two-thirds compressed and proper tension maintained across the entire cover.
  • Monitor the water level to ensure water is not freezing at the tile line or within the skimmer throat.
  • Regularly remove leaves from the cover and monitor water chemistry. If ice exists (like in the picture above), don't try to remove it - you can damage the cover.
  • Some mesh pool covers can filter water down to 20 microns before it enters the pool. But to prevent cloudy water and pool stains with a mesh cover, maintaining proper water chemistry is vital. Use pool enzymes, and maintain proper chlorine and algaecide levels during the winter to drastically reduce spring clean-up and lower your start-up costs.

Solid Safety Cover w/ Mesh Drain Panels (Inground Pool): 

  • Mesh drain panels in the center of the cover help to concentrate silt and runoff water in one location directly beneath the drain. Just like with a completely mesh cover, try to keep the cover free of excess debris so it can work properly.
  • Check that all straps are connected to the deck anchoring system, with the springs two-thirds compressed and proper tension maintained across the entire cover.
  • Solid covers should allow water accumulation at all areas to drain to a center point. Adjust straps if water pools in area other than the drain location.
  • Ensure that the drain panel is unblocked so draining water has ability to pass through into the pool.
  • Remove leaves and monitor water chemistry during th. If ice has stuck the cover to the pool, just leave it be - it will thaw eventually.
  • Monitor water levels to ensure water is not freezing at the tile line or within the skimmer throat.

Solid Safety Cover (Inground Pool): 

  • In theory, nothing enters the water when using a cover pump and a solid cover, so water chemistry is highly unlikely to go bad. The main goal is to make sure the cover pump continues to work.
  • Solid covers should allow water accumulation at all areas to drain to a center point where pump is located. Adjust straps if water pools in area other than pump location.
  • Remove leaves and monitor water chemistry.