Swimming Pool Blog

How to Winterize an Inground Pool in 10 Steps

How to winterize an Inground Pool
by Rob Cox, September 19, 2019


How to Winterize an Inground Pool in 10 Steps

how to close your inground swimming pool
For those of us living in the snowbelt, temperatures will soon approach 32 degrees, and unless your filter pump is running, freeze damage can result. Pipes, heaters, filters, pumps - all are made from strong materials, but all will crack from the expansion of ice within unless proper precautions are taken.

This article will explain how to winterize your inground pool. All pools are slightly different in system design, your pool may require additional steps or sub-steps to remove all of the freeze damage hazards. If you have questions on your specific pool and the closing process, get in touch with us, and we'll help make sure you are well protected from winter's worst.

chlorine free pool shock1. Balance your Pool Water. Adjust your pH, total alkalinity and calcium hardness levels in the pool. Do this about a week before pool closing, so that you can adjust again if needed. Shocking the pool with granular chlorine is a good idea before closing the pool, but this should also be done 3-7 days before closing. This allows the chlorine level to normalize before covering the pool. High chlorine levels can weaken your winter pool cover and destroy your winter algaecide and stain prevention chemicals.

2. Clean the Pool Thoroughly. The cleaner the pool is when you close it, the better it will look next spring. Any debris or algae left in the pool during closing will dilute the strength of your winterizing pool chemicals, as they will go to work on organic matter left in the pool, leaving less available for winter. Organics in the pool will also increases the chance for pool stains. Vacuum, brush and skim the pool, then skim the pool again, just before covering the pool.

3. Lower the Pool Water. For pool safety covers, lower the water to a maximum of 18" below deck level. For winter pool covers, the type that float on the surface and are held in place with water bags, lower the pool water level 3-6" below the skimmer opening. If you have a vinyl liner, you can also make use of a product called a skimmer plug, which fits inside of your skimmer opening to block water from entering. Just snap it on the front of the skimmer, and you don't need to lower the water level at all.

Poolcenter.com Winter Kit4. Add Winter Pool Chemicals. Many pool owners use a pool closing kit, which usually contains algaecide, non-chlorine floaters, stain and scale preventer and some non-chlorine shock. Follow the instructions on the package. It's best to add the stain & scale and the non-chlorine shock 3-7 days before closing, and add the algaecide and floaters just before covering the pool. If you have a mesh safety cover, we recommend using a pool enzyme product to help control algae growth during the winter.

5. Clean the Pool Filter. For DE filters, remove the assembly from the filter tank and hose it clean to remove all DE powder. DE powder left to dry on the grids during the winter can cause clogging of the fabric, creating filtration problems the following spring. If you have a cartridge filter, the same rule applies: remove the cartridge and hose thoroughly. After blowing the lines, place your grid assembly or filter cartridge back in the filter tank for safekeeping during the winter. Make sure that you tightly secure the filter lid and clamp band before and after blowing lines. Loose or improperly secured filter clamp bands can cause the filter lid to blow off during start-up.

6. Remove Drain Plugs. They'll need to be removed from the pool pump(s), filter, heater and chlorinators. Look over all the pipes and every piece of equipment, looking for and removing any drain plugs you see. Store all of the drain plugs in the pump basket or another safe location. Place multiport valves in the Winter position, and slide filter valves in a mid-way position.

cyclone blower7. Blow the Lines Out with Air. This is the most important step in the process. Blowing out the equipment and underground plumbing ensures that there is no water left to cause freeze damage. You can blow out the lines using a Cyclone blower, or you can use a powerful shop vac or small air compressor. Direct the air backwards through the suction lines to blow out the skimmers. Once the suction lines are plugged, direct the air through the pump (removing the volute drain plug) through the filter, heater, chlorinator, and finally out of the pool return lines.

If you choose not to blow out the lines, lower the pool water level and make sure that all of the equipment is completely drained. Then use a hose and funnel to add non-toxic pool antifreeze into the skimmer and return lines, at a rate of 1-gallon per 10 feet of pipe.

8. Plug the Lines. Use pool plugs to plug skimmers, returns and cleaner lines. Make sure to plug them all! You don't want any pool water returning to the lines after you've winterized them. Replace any plugs that show signs of dry rot, or do not fit tightly.

skimmer guard gizzmo plug9. Add Skimmer Bottles. You can use a skimmer guard, which is a combination skimmer plug and ice absorption device. If you are plugging the skimmers with rubber freeze plugs, then use an empty winter algaecide bottle, empty except for a few inches of pea gravel in the bottom. This will weigh the bottle down and allow it to float partially submerged. When the water rises in the skimmer and freezes, the expansion of the ice will collapse the bottle or skimmer guard and not break the outside walls of your skimmer. BONUS TIP: Use a 12" square of plastic bag placed under the skimmer lid, to block rain water from seeping in around the lid.

10. Cover the Pool. The final step is covering the pool, although you can cover the pool earlier, if you need to keep it clean, while completing other details. Before covering the pool, check that your pool cover is not very dirty, or has holes that need mending. Apply cover patches as needed - there are poly patches for solid winter covers and mesh or solid patches for safety covers. Secure your pool cover very tightly, to keep out wind, debris and small animals.



That's about it! As mentioned earlier, every pool is a little different. Just make sure that all of the water is removed from the plumbing (with the exception of the main drain, which may not blow out) and from the equipment. Do NOT cover the equipment with plastic, as this can trap moisture and create rust. That said, heater covers are still a good idea, and won't trap moisture.

If you have any questions on winterizing your swimming pool, just click the link at the top of the page and let us know. You can do this!