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How to Winterize Your Pool

By Team Royal - Updated On: 10/10/23

Winterizing your pool properly can prolong the life of your pool, extend your investment, and save yourself hours of hard work come springtime. Here’s your complete checklist for proper pool winterization.

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First Things First: Supplies & Cleaning

Before closing down your pool for the winter season, the single most important thing to do is make sure that your pool is chemically balanced. The calcium hardness and total alkaline should be balanced, as well as your pH levels. If you forget about this important step, you may have to deal with etching or staining on the surface of your pool (which could cost you hundreds of dollars, come springtime!) Purchase a winterization chemical kit for your pool—an easy one step method—for ensuring your pool stays balanced and healthy all winter long. Before making sure your pool is balance, it’ll have to be clean!

You will want to clean out any debris from your pool by either a dip net or a skimmer net. If you have a heavy patch of leaves you may want to use a leaf vacuum.

leafvac skimmernet dipnet
Leaf Vac Skimmer Net Dip Net

Next up for cleaning, you will need to brush all the walls, steps and anything else that may have debris or ladders, swim-outs etc. Make sure you use the proper brush for your type of pool.

ladderbrush wallbrush

Once the debris is out of the pool and the pool has been completely brushed, it's time to vacuum the pool.  Like the brush, you want to make sure you have the proper vacuum for your pool. There are several types of vacuum heads. When vacuuming your pool you want to make sure to take steady rhythmic passes to insure that you get the pool as clean as you can.  Just remember, the cleaner the pool is when you close it, the easier it will be to open next season.

vacheads vacuuming

Now that you have vacuumed your pool, it is time to check water chemistry and adjust the levels if needed. After the chemistry has been checked and adjusted, remove the ladder, fountains, floats, and anything else that does not need to be in the pool, then add your winterizing chemicals.

Which Winter Chemicals Do You Need?

You will need the following chemicals along with the ones used to balance your pool.

Shock - use the same shock you use during the regular pool season.  Double the dosage for the winterizing.

Algaecide - You will pre-treat the pool with algaecide.  Follow instructions listed on the individual bottle.

If you would prefer to use a pre-formulated blend, we highly recommend Pool Magic - it is a natural enzyme formula from Natural Chemistry which helps to get your pool set for winter!

Now if you don't want to play pool chemist, there's also EZ-POOL, which we recommend for anyone who wants to get the job done right without having to think about which products they need to use for different purposes. 

Now that your pool has been treated, lower the water lever and remove any water from the equipment and plumbing. The water should be lowered below the skimmer according to the type of pool cover you're using:

  • For a mesh cover, lower the water 12 to 18 inches below the skimmer.
  • For a solid, floating cover, lower the water to 3 to 6 inches below the skimmer.

Make sure that you have all the water out of the plumbing. You can accomplish this (either by pump or by blowing out the lines with air). Next, you want to remove all the plugs from the pool equipment and follow any special instructions listed in the owner's manual for the pump, filter, heater, or any other pool equipment.

Lastly, stow away your pool maintenance tools ( nets, vacuums, vac plates, hoses, etc.) and cover your pool until next season!

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Don’t Forget When Water Freezes, it Expands!

Make sure to think one step ahead of the cold weather that’s coming—when the temperature drops, your pool water may freeze and if that happens, the water within will expand. If you’re dealing with freezing temperatures, this can cause quite a bit of damage to your pool’s siding and plumbing system.

Assuming you have vacuumed, removed auto cleaners and put in all necessary winterizing chemicals, first thing is determining if you have a flooded or non-flooded system.

Flooded System

If your equipment pad sits below the ground level of your pool, then you have a flooded system.

Having this type of plumbing requires that you blow out all the water from your lines and cap them on the end. There are several ways to do this, yet the way we’ll discuss what we have found to be the easiest and least amount of labor.

Make sure you have plugs available for each of your return lines and Gizmos for each of your skimmers.

  1. Remove the eyeball portion of each of your returns as to leave just the threaded end of the plumbing. If it’s not threaded you can use rubber plugs.
  2. Open all of the valves on your suction header and return lines.
  3. With your pump turned off place the multi-port valve on recirculate.
  4. Take your wet/dry shop vac with blower function over to one of your skimmers.
  5. Remove the lid and basket.
  6. Place the end of the hose down inside the plumbing at the bottom of the skimmer. One person may need to hold it in.
  7. Turn the vac on making sure it’s on blower. In just a short time you will see big bubbles coming from one of your return lines.
  8. Go to the return bubbling and place a plug inside stopping the flow of air and keeping any water from going back inside. Not long after putting in the plug, another line will pop.
  9. Continue the same way placing plugs in as the lines blow.
  10. After all the returns are capped, the other skimmer will go. Plug it with a Gizmo or similar type plug.  The very last thing that will go will be your main drain.
  11. Once bubbles start coming from the main drain close the valve to it on your suction header. This will create an air lock and keep water from going back into the main drain. Be sure to turn off the blower right as you close the valve to prevent any plugs from coming out.
  12. Immediately put a Gizmo in the skimmer you were using to blow.
  13. Remove the drain plugs from your filter, pump, chlorinator, mineral feeder, ect.. If you have a salt system you unscrew the unions and remove your cell. 
  14. To ensure that the water is out of your backwash line you can drill and tap a hole at ground level. Tap with 1/4 or 1/8 inch, whichever plug you will put back in when opening.  Doing it this way eliminates the need to drain the water below your skimmers and returns.

Depending on what part of the world you live in and what your climate is like will determine what your ground freeze depth is. If you live in colder climates it may be safer to take these steps even if you don’t have a flooded system. Refer to your local water supplier to ask what your freeze depth is, then determine whether or not your plumbing sits below that depth.

Non-Flooded System

If you feel confident that your plumbing sits below the freeze level and you DO NOT have a flooded system you can just drill and tap all lines EXCEPT the main drain at ground level. All of the water at risk of freezing will run out the hole.

Your pool is now winterized and ready to be covered.

To be sure your pool is properly protected in the coming months, enjoy peace of mind with one of our winter pool covers. They are specially designed and woven with polyethylene, a durable and long lasting material that will stand up to the harshest winter weather. Each of our swimming pool covers can be custom made, and come with a storage bag, stainless steel springs, brass anchors and a tool for easy installation.

Don’t Forget About Your Winter Accessories

Before closing up your pool for the season, make sure you’ve got all of your supplies on hand: winter covers, water tubes, plugs and seals; and winter cover patch kits.

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Water tubes will help to ensure that your pool cover is adequately securing your pool water from the low winter temperatures, while winterizing plugs and seals will prevent freezing water from plugging up your pool’s plumbing system.

Lastly, keeping cover patch kits on hand is an excellent way to be prepared in the middle of winter, when you need a quick and easy fix for your pool cover leak (which can happen due to extreme weather conditions).