As more people embrace the pumpkin spice and cozy sweaters of autumn, the time frame to close your pool while it’s still nice outside gets cuts shorter day by day gone by. Whether you just haven’t gotten to it yet or just don’t know where to start, every responsible pool owner knows that winterizing their pool is vital to its condition, especially as the first unexpected freeze approaches. While it may be a process to cover your pool, it’s best to do it when the weather is mild, debris isn’t severe, and you have a good timeframe to distribute all the right chemicals for a bright blue pool at the end of next spring. But wait…what are the “right chemicals”?

 If you’re looking for the answer to this question, look no further. It’s closing time, and we want to tell you the 8 kinds of chemicals you may need to close your pool up this season for glistening water in the next one. Check out our list below.


  1. pH adjusters: your pool’s pH should be between 7.4 and 7.6 in order for other chemical additives to work efficiently, so it’s crucial that you have either a pH increaser (soda ash) or decreaser (muriatic or granular acid) to make adjustments to the level. A tip is to keep checking the pH as you add chemicals, so the water doesn’t become too basic or too acidic.
  2. Alkalinity adjusters: alkalinity is similar to pH; you need to have an increaser (sodium bicarbonate) and decreaser (muriatic or granular acid), keeping the level between 80 and 120 ppm. Keep these additives small in dosage– you could potentially throw off your pH balance.
  3. Water hardness adjusters: hardness refers to the amount of calcium dissolved in the pool water, and your ideal hardness depends on your specific pool type. Increase the water hardness by adding calcium chloride or decrease it with muriatic acid or sodium bisulfate.
  4. Oxidizer/shock: adding an oxidizer will dissolve organic matter in your pool. Sometimes it’s chlorine, but to avoid increasing chlorine levels too high, many pool owners use Permonosulfate instead. Shocking your pool is key before closing to ensure it stays clean all winter.
  5. Algaecide: a good dosage of algaecide in your pool before a long winter will keep algae growth at bay. This needs to be a strong dose to maintain its effect for a few months, but it also needs to be added when the chlorine level falls below 3.0 ppm to work completely.
  6. Scale Inhibitor/Metal Sequestrant: to avoid any metal staining on your liner or pool parts, a scale inhibitor or metal sequestrant is necessary. These chemicals keep metals suspended in the water if present, ensuring they don’t stain any surfaces. Scale inhibitors also prevent cloudiness from high calcium levels, but if the water hardness is properly adjusted this shouldn’t be an issue. This chemical is usually active for many weeks.
  7. Chlorine or Bromine: also used as shock/oxidizer and a general sanitizing agent, chlorine is the most common sanitizing chemical in traditional pools, but many household also use bromine as an alternative.
  8. Stabilizer: added to stabilize chlorine and often included in a pool sanitizing kit already, a pool stabilizer is usually a chemical called cyanuric acid. This chemical makes the chlorine less reactive to sunlight, getting you the most out of your chemical treatments.

 As you can see, pools are filled with numerous different chemicals to stay blue and shining all winter long under your cover. If you want that sparkling oasis in the spring when that cover comes off, take note of these chemicals and their uses. Be very specific about your leveling for the winter season, ensuring you don’t cause your pool any unneeded damage. Keep checking the levels when adding chemical after chemical for winterizing so you maintain the ideal balance. Happy pool closing!