Short List of Chemicals Do I Need to Close My Pool

While it’s fun to get out and enjoy the fall season, it’s important to keep the pool closed to protect it from the elements.

Getting the proper steps in place to close your pool makes it look great the next time you open it. Winterizing it can also help keep it running smoothly.

What Chemicals Do I Need to Close My Pool

Many of the chemicals you use for pool maintenance are also used to close a pool. These chemicals are also used to keep pool water clean during the winter months.



An element in the form of solid calcium hypochlorite tablets or granules or liquid sodium hypochlorite.

Here is why you need it:

  • Keeps water clean
  • Destroys harmful bacteria
  • Keeps algae away

Tips for usage: when your pump doesn't run during the winter, try taking a chlorine pill once a week to keep the chlorine in your system at a steady level. It's also a good idea to try a floating chlorine bottle.


Pool Shock

High dose chlorine or non-chlorine potassium peroxymonosulfate sanitizes pool water

Here is why you need it:

  • Removes contaminants
  • Destroys chloramines
  • Breaks apart harmful bacteria

Tips for usage: add chlorine-based pool shock up to a week before closing your pool. Non-chlorine pool shock can be added a few days before closing the pool.


Soda Ash

Sodium carbonate (Na2CO3) is a chemical content with an alkaline pH of 11.3-11.7

Here is why you need it:

  • Raises pool pH
  • Raises total alkalinity
  • Less expensive to use than baking soda


Tips for usage: don’t add too much soda ash or it could make your pool water cloudy.

Baking Soda

Sodium bicarbonate (NaHCO₃) is a chemical compound with a mildly alkaline pH

Here is why you need it:

  • Raises total alkalinity
  • Raises pH slightly

Tips for usage: this common baking ingredient helps balance your pool’s pH and total alkalinity.


Muriatic Acid

Muriatic or hydrochloric acid is used to balance total alkalinity and pH of pool water

Here is why you need it:

  • Lowers total alkalinity
  • Lowers pH

Tips for usage: this acid is too strong for vinyl-lined or fiberglass pools. It can destroy these pool materials.


Winter Algaecide

This chemical prevents and kills algae growth.

Here is why you need it:

  • Kills algae
  • Prevents new algae growth
  • Releases when temperatures get warm

Tips for usage: add to water one day before closing your pool. Winter algaecide lies dormant until temperatures rise in the next spring season.


Pool Antifreeze

Chemical that prevents pool plumbing from freezing

Here is why you need it:

  • Protects pipes from freezing
  • Prevents expensive plumbing repairs

Tips for usage: either completely blow out pool lines in an inground pool or add antifreeze if you live in a cold climate. Consult a pool professional for help.


Stain and Scale Prevention

These chemicals prevent the buildup of metals and minerals

Here is why you need it:

  • Prevents metal build-up
  • Prevents metal staining
  • Prevents mineral build-up during winter months
Tips for usage: add stain and scale formulas before you disconnect the pool pump. You want the pump to distribute the stain and scale chemicals throughout the pool.


This post was originally published on Swimming Pool

If you have any other questions about pool and spa products please do let us know - we are here to help!

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