Unless you're lucky enough to live in a tropical location where you can use your pool all year long, you'll have to winterize it at the end of the season. Many pool owners view Labor Day as the end of the swimming season and start their pool closing tasks soon afterward. But in warmer climates (or if you have a pool heater), you may be able to extend your pool season well into November. However, you'll still need to winterize it, and draining some of the water is a crucial step of routine pool maintenance.
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Here's how much water you need to drain from an in-ground pool and an above-ground pool for the off-season — and special rules you need to know if you're using a mesh safety cover.
Why Do You Need to Drain Pool Water in the Winter?
You need to remove a few inches of water from your pool in the winter to accommodate for water expansion. When water freezes, it expands. If you don't make room for that expansion, the water will push on the pool walls and the pool equipment, such as the skimmers and return jets, potentially causing damage. Making sure the water level stays below these two parts of the pool will keep water from flowing into other pool equipment and damaging it.
While lowering the water level in your pool is important, you don't want to go overboard and completely empty the pool. An empty pool is exposed to frigid air without the water to provide a buffer. This cold air can dry out pool liners and rip, crack, or tear them, leaving you a big headache for next season. If you have an in-ground pool, you want to keep the water level in the pool above the groundwater level. If it dips below this level, freezing groundwater around the pool can damage a fiberglass pool shell or even pop it out of place.
What Happens if You Don’t Drain Water From Your Pool in the Winter?
If you don't drain some water from your pool during the winterization process, you're very likely to have a damaged pool come next spring. Cracked skimmers are a common occurrence, as are damaged walls and liners. An overfilled pool can also allow water to make its way into the pumping system, where it can freeze and damage the pool pump or associated plumbing.
As ice expands in an overly full pool, you also need to worry about structures around the pool itself. Ice overflows can damage wooden, tile, and concrete decks surrounding swimming pools.
Additional Pool Closing Tasks You Need to Do Before Winter
In addition to draining the water before the winter, you also need to do the following to properly close your pool:
- Clean the pool
- Test and balance the water chemistry (adjusting the alkalinity, chlorine levels, calcium hardness, and combined chlorine)
- Add winterizing chemicals like pool shock to ward off algae growth
- Clean the pool filter
- Remove all water lines
- Remove or replacing drain plugs
- Shut off the power to the pumps
- Remove deck equipment
How Far to Drain an Above-Ground Pool for Winter
If you have an above-ground pool with a vinyl pool liner, you don't have to drain the pool at all if you install a skimmer cover and return line plugs. Otherwise, drain the pool to just below the skimmer and the top return jet, which is typically a few inches below the skimmer. This will ensure that water doesn't enter your pool's plumbing via the return line and freeze over the winter.
Draining too much water from an above-ground pool can damage the vinyl liner. Follow your pool manufacturer's recommendations for setting the winter water level.
How Far to Drain an In-Ground Pool for Winter
Fiberglass and vinyl in-ground pools can sustain damage if the water level in them is too low. As such, the best way to winterize them is to lower the water no more than 4 to 6 inches below the skimmer and use a blowout kit to protect the skimmer and return lines. If you have a concrete pool, you can drain the water to a level beneath the return lines instead.
It is also of note that if your pool contains decorative ceramic tiles, it's best to get the water level beneath them if you can. Otherwise, freezing water may crack or break the tiles.
Here's how to drain water from a pool using the pool filter:
- Attach a pool hose to the filter and direct the other end of the hose to an appropriate drainage area or drain.
- Turn off the filter, set it to "backwash," and then turn it back on.
- Backwash for about 60 seconds. Then, turn off the filter and set it to "waste."
- Turn off the skimmer and open the main drain.
- Turn on the filter to start draining water.
How Much Water to Drain if You Use a Winter Cover
There is one exception to the standard rules for above-ground and in-ground pools, and that is a mesh cover. A mesh cover is a porous cover that keeps out dirt and debris while allowing your pool to fill up gradually with precipitation. These winter pool covers help fight evaporation during a long winter and prevent a heavy snow buildup on the pool cover, but they require you to drain more water since, during the winter months, water will slowly be added to the pool.
If you plan on using a mesh pool cover, you may want to lower the pool's water level a bit further to allow room for snow and rain to enter the pool. You'll also need to check the pool's water level periodically during the winter in case the water threatens to creep up over the return lines (roughly every couple of weeks or so). If it does, you'll need to drain some more water from the pool.
Mesh pool covers are most commonly used on in-ground pools, but they are manufactured for above-ground pools as well. Like solid covers, mesh covers can be allowed to float on top of the water, so resist the urge to pull them tauter than they need to be, to prevent rips and tears.
Drain your above-ground or in-ground pool to:
- 6 inches below the skimmer or the bottom of the returns when using a floating cover
- Up to 12 inches below the skimmer when using a mesh cover
To help brace for the weight of snow and ice during the freezing temperatures, you can provide additional support for your pool through an inflatable air pillow (like this one from Amazon). To use one, simply put it in the center of your pool before you cover it.