Pool Winterizing 101: Everything You Should Know

Once summer fades and autumn begins to paint the leaves, it’s time to prep the pool for the colder winter months. Pool winterizing is especially important in climates that feature significant amounts of ice, snow, and subfreezing winter weather. It’s a good time to close a pool once high temperatures dip to below about 65?F. Starting too early, however, may lead to problems with algae, which spreads readily when temperatures are too high.

Yet it’s best not to wait too long either, as pool winterizing should be done before temperatures get too cold. When pool winterizing is done right, it ensures the pool will be ready to open in spring without too much work. Done haphazardly or incompletely, and pool owners can instead look forward to quite a bit of unnecessary work prior to the next swimming season.

The following steps for swimming pool winterizing can be done over the course of a few days:

1. Removing Accessories

Pool parts and accessories should be removed from the pool and hosed off with water to remove algae and dirt. The skimmer and pump basket should be rinsed off as well.

This means removing:

  • Heaters
  • Ladders
  • Pool cleaners
  • Pool handrails
  • Pump baskets
  • Skimmer
  • Slides
  • Solar blankets
  • Vacuums
  • Wall fittings

Any other pool equipment should also be removed and, once rinsed, should be set aside to dry. Accessories should then be packed away for the winter in a garage, pool room, shed or another dry place.

2. Cleaning the Pool

Everything left that isn’t water should be removed at this point. This includes leaves, dead insects, dirt, and other debris. Use either a pool vacuum or leaf net for this. Clean tiles and vinyl around the waterline with a specialized cleaning agent to prevent algae or mold from growing. This will also make it easier to balance the water’s chemistry.

3. Balancing the Chemistry

Just like during the swimming season, pool winterizing involves balancing the chemicals in the water to prevent corrosion, algae growth, or calcium scaling.

About 3-7 days before closing the pool, adjust the water accordingly:

  • Alkalinity level at 80-120 ppm (parts per million)
  • Calcium hardness level at 180-220 ppm
  • pH level at 7.2-7.6

Once these levels are reached, shock the pool using chlorine, or a non-chlorine substitute, to bring chlorine levels to 10-12 ppm. Wait until chlorine levels drop back to a normal range of 1.5-3.5 ppm before adding algaecides or chemicals for winterizing. These keep the water clear for the start of the next swimming season. Larger pools may require larger quantities of these chemicals.

Avoid using floaters with strong oxidizing ingredients like chlorine or bromine. These tend to stick against the wall, causing stains, especially for pools with vinyl liners. For this reason, it’s also not a good idea to put chlorine or bromine tablets into the water. They’ll sink and damage the floor of the pool.

4. Cleaning and Backwashing the Filter

Next, the filter needs a thorough backwash and cleaning. Drain DE (diatomaceous earth) filter tanks, leaving the backwash valve open. With sand filters, you will want to first unplug the filter drain plug before leaving it off. The drain plug should then be dried and stored with all the other pool accessories.

Meanwhile, make sure there’s no water in the multiport valve. If necessary, a specially designed pool winterizing blower can clear the pool’s water lines. When preparing an above-ground pool, however, winterizing requires that hoses and plugs are disconnected and plugged rather than drained.
DE filters don’t need an acid wash when preparing the pool. Winterizing with muriatic acid can degrade a filter’s components. Springtime is best for this.

5. Lowering the Water Level

Even pool owners in areas where it rarely freezes should take precautions against possible damage from freezing temperatures. Using either a submersible pump or filter pump, drain water to a point below the skimmer’s mouth.

Water should be lowered about 12-18 inches below the skimmer for pools with mesh covers. For those using solid floating covers, water should be lowered to 3-6 inches below the skimmer. The water level should be about 4-6 inches below the lowest plumbing line, likely the water return line.

Never completely empty all the water from a pool. Doing so will cause the soil beneath it to expand during a hard freeze, which can lift the whole pool out of the ground. Water helps prevent this, keeping the pool (and the earth) firmly in its place.

6. Draining Equipment

Water left in pool equipment will expand and damage it if temperatures fall below 32?F. Drain plugs allow the water to empty easily. Ensuring pumps, filters, heaters and chlorinators are drained and blown dry will prevent cracking during freezing weather. It also protects the plumbing lines.

Once drained, the cartridge filters or DE filter grids should thoroughly be cleaned. If the pump and filter are small enough, store it indoors. If not, blow out any water with a pool winterizing blower. Add pool antifreeze as an added safety measure to prevent pipes from bursting. The plugs should be kept out. Put the plugs all together in the skimmer basket or other easy-to-find location for when they’re needed next spring.

7. Covering the Pool

Pool winterizing requires a different type of cover. Winter covers are more robust to withstand the weight from ice and snow. They also protect pets or people from falling through and into the water. Because of this, winter pool covers shouldn’t have holes or gaps and should fit tightly.

Mesh safety covers work well for inground pools, offering the best protection for the pool while also keeping people and animals safe. Either mesh or solid winter pool covers work for aboveground pools, though these only protect the pool and aren’t necessary for safety.

Additionally, with an aboveground pool, winterizing should include installing and anchoring an air pillow in the center. This helps absorb expanding ice within the pool while also keeping snow from applying too much pressure.