Winterizing Your Aquatic Facility

The leaves are changing, crisp air and rain are in the forecast — here in the Northwest, fall is officially here. And with that, the end of outdoor swimming season. As temperatures drop, you’re faced with the task of winterizing your inground pool in order to protect your facility’s aquatic equipment, interior finishes and tile, plumbing and more. It can feel like a lot to undertake, but breaking it down into steps with proper care can help minimize damage and the headaches that severe winter weather can create for aquatic facility managers. We’ve got some crucial and well-informed pointers from our friends at Pool & Hot Tub Alliance below. 

Another important thing to remember is that you don’t have to go this alone. If you have any questions or concerns about your facility as you’re winterizing it, speak with one of our trained consultants by giving us a call at (877) 828-0072 or

Water Treatment

As a starting point, most winterizing processes recommend balancing the pool water to PHTA standards. (See table below.) Consideration should be given to the fact that as the water temperature decreases the Langelier Saturation Index (LSI) will decrease (water will become more corrosive). This balancing process should take place 3-7 days prior to closing the pool. These levels should be adjusted and then rechecked using proper testing equipment.

Parameter Min  Max Ideal Range
pH 7.2 7.8 7.4-7.6
Total Alkalinity, ppm 60 180 80-120
Calcium hardness, ppm 150 1000 200-400
LSI -0.3 +0.5 0.0 to +0.5

At initial closing, it may be preferable to balance the water in a positive range allowing for the fact that as the temperature drops the LSI will drift downward. For chlorine and bromine pools, the pool water should be shocked using a chlorine product to remove residual swimmer waste, kill bacteria and algae, and remove other organic contaminants from the water. Additional oxidation may be performed with a non-chlorine oxidizer. The chlorine and other oxidizer residuals should be allowed to decline prior to adding additional closing chemicals such as algaecides and sequestering agents that may be degraded by high levels of oxidizer.

For PHMB (biguanide) sanitized pools, the pool water should be oxidized with hydrogen peroxide.

The use of an EPA registered algaecide is recommended due to the lack of winter filtration and the use of certain types of covers which may allow sunlight and fine organic debris and contaminants to enter the pool’s water.

Balancing the water is the first step in preventing staining to interior finishes; however, the use of an appropriate stain preventative is recommended in many regions of the United States due to the length of time the pool is shut down. Many commercially available winterizing kits will often contain sequestering or chelating agents. Always check with the individual manufacturer of the winterizing kit as to the best practice for use during the pool closing process.

Clean the pool. This should include a thorough brushing of all the surfaces, including, but not limited to walls, coves, and floor. Skim the pool’s surface and remove any floating leaves and other organic debris. Vacuum the pool.

After taking care of the water treatment, the following procedures should be performed. The topics here are not listed in the order that they should be performed. The order will vary depending on the location and type of equipment used.

Filtration Equipment, Pumps, Heaters, and Chemical Feeders & Controllers

Clean the filter. Backwash several times if a sand or DE type filter. If a cartridge filter, then remove and clean the cartridge(s), allow them to dry and then store for the winter in a warm dry indoor location. DE grids can also be cleaned, removed, and stored indoors. Empty all chemical feeders (please see precautions below). Drain your pump, filter, heater, and chlorinating equipment. Place the drain plugs in the hair and lint (pump) basket, so that you can find them in the spring.

This pool has been properly closed and ready for winter.

Purge any remaining water from the pump, heater, heat pumps, chemical feeder and other wetted equipment. Care must be taken to use the proper procedures and equipment (e.g. wet/dry shop vacuum, low pressure air compressor, etc.) since pool equipment and lines cannot take excessive pressure and overpressure could present a safety hazard. This process should only be performed by an appropriately trained professional familiar with the potential hazards associated with pressurized air.

Make sure the electrical power to any heaters or heat pumps is disconnected and the circuit breakers are in the “off” position. Turn off the pilot flame, main gas valve and gas supply to the gas heater. Drain any water from the heat exchanger in accordance with the manufacturer’s directions.

Make sure the circuit breakers are in the “off” position. In severe snow areas, the motors should be removed from the pump housing and stored indoors in a dry location. If a motor is left outdoors, make sure it has a weatherproof protective cover.

If the pool has an electrolytic chlorine generator, make sure there is no standing water in the cell. Remove the cell and store indoors. If the pool utilizes Automated Controllers and Chemical Feed Equipment, be sure the electrical power to the controller is disconnected. Remove any sensors from the flow cells then, clean and store them in accordance with the manufacturer’s instructions. Empty the flow cells then, clean and allow them to dry before storage.

If peristaltic pumps are used, remove any feed and injection tubes then clean and allow to dry before storage. Store any chemicals in accordance with state and local codes.

Automatic controllers that are installed outdoors should be removed and store indoors or protected from the extreme effects of winter.

Many pump, filter, and heater equipment manufacturers have specific instructions for safeguarding their equipment. Always check with the respective manufacturer if you have any questions.


The main damage to plumbing lines occurs from the freezing of water in these lines. By using an air compressor or the discharge side of a shop vacuum, you should purge the water by blowing air through the lines until bubbles appear inside the pool. This includes all return lines, suction lines (skimmer and main drain) and lines to water features, solar heating, pool cleaners, and slides. Again, caution is advised on the use of pressurized air. On return lines, you will want to remove the wall fittings and insert tapered expandable plugs once the lines are clear of water. Tighten in place. In some locations, severe freezing water may dictate the use of straight pressure plugs.

Suction outlet (main drain) lines should have air blown through them until bubbles appear in the pool then plug the pipe topside or close the valve to the suction outlet. The idea is that you will create an “air lock” in the line preventing water from re-entering the lines.

Skimmer lines must be purged with air and then once bubbles appear screw in a threaded expansion plug into the skimmer. These devices will prevent freezing water from expanding and cracking the skimmer. Use an appropriate (e.g. PTFE) plumbing tape on the threaded fitting to insure a water-tight seal.

Lowering the Water Level

The issue of draining water from the pool and the amount is often based on regional differences and the type of cover (solid or mesh) used on the pool. Issues such as the amount of rain, snow, and snow melt will often influence the amount of water drained. It is always prudent to consult with your winter cover manufacturer as to the proper amount of water to be drained to avoid damaging the cover. In addition, one must take into consideration the fact that freezing pool surface water can damage waterline tiles, prematurely dry out vinyl liners, and expose plaster surfaces to the atmosphere which can create cracking and defined water line indications on the surface.


Prior to installing winter covers, ladders, diving boards, and handrails should be removed, cleaned and then stored in a dry place.

On all covers, leaves and other organic debris must be periodically removed to prevent plugging the cover pump or damaging the cover.

Tracked solid covers must be monitored for accumulation of water, snow, and ice. Excess weight from these items can damage the track system, possibly damaging the concrete, coping or pool wall.

With all winterizing covers, the long term durability and longevity of the cover is dependent on proper water balance, proper water levels under the cover, regular maintenance and cleaning.

Safety covers keep your pool protected from accidental entry and help prevent dirt, debris and leaves from entering during the winter months. We also love them for their durability.


Winterizing or closing should occur before the first hard freeze. Make sure to  consult with the various chemical manufacturers, pool manufacturer or builder, equipment manufacturers, and cover manufacturers for the correct procedures and processes to use for where your climate.


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