What is Shocking a Pool?

Shocking a pool is a process that every pool owner must know. But what is shocking a pool? “Shocking” is another term for super-chlorination, which involves adding chlorine or non-chlorine chemicals to a pool to oxidize chloramines, sanitize the water, and destroy bacteria and other harmful pathogens. 

Pool shock treatment must ideally be done every week, especially if your pool sees a lot of activity–but you don’t have to spend a pretty penny to hire someone to do it every time.

Understanding Chlorine

Before finding out how much shock to add to a pool, we must get to know chlorine and how much of it a pool needs.

Chlorine is the top disinfectant for most pools. It comes in liquid, powder, or tablet form (and, uncommonly, as gaseous chlorine), and it’s added to a pool to get rid of pathogens that can damage parts of it and harm people swimming in it.

Shocking a pool is primarily done to deal with the amount of chlorine in the pool. We want a lot of free chlorine (FC) or the chlorine that actively disinfects the water, killing potentially harmful things in the water and releasing them as gas in the atmosphere. The FC level should be between one and three parts per million (PPM) so that it does its job. However, after a pool is used, combined chlorine (CC, also known as chloramines) builds up. CC refers to chlorine that has mixed with other bacteria chemicals introduced into the pool, including sweat, makeup, sunblock, etc. This type of chlorine has low sanitizing power, so it’s best to keep it at levels less than 0.2 PPM.

Shocking a pool releases CC and off-gasses a pool’s contaminants, increasing the level of FC. Generally, you’ll need to raise the FC by ten times the level of CC to make this effective, which is why it’s better to shock your pool weekly so that you never have to deal with excessively-high amounts of CC.

Why Do I Need to Shock a Pool?

Shocking a pool is necessary to keep it clean, which it does by stabilizing the levels of chlorine in the water. The process kills chloramines and any other bad stuff that could get into the water and keeps your pool at a good level of FC, which could even go down due to weather conditions.

Having a clean pool ensures that your water is clean and clear, and safe to swim in. Plus, it protects anyone swimming in your pool from any negative side effects that could come from leftover pathogens in the pool, such as skin irritation or red eyes.

How to Shock a Pool

Shocking a pool is easy; it’s something that you could do yourself with the right tools and chemicals. Here’s a quick overview of the steps to do it:

1. Wear the necessary equipment (e.g. gloves) to protect yourself as you use pool chemicals.

2. Prepare your pool shock, following the manufacturer’s instructions and figuring out how much to use.

3. Pour the poor shock into the pool.

4. Leave the pool shock alone to do its thing. It’s typically recommended to leave it overnight (or twelve hours).

5. Check the chemical levels of your pool.

6. Run your filtration system for twenty-four hours to remove any germs or algae in your pool.

After these six easy steps, you can now enjoy your pool! 

When to Shock a Pool

It’s recommended to shock your pool once every week, but more frequent shocking may be required if your pool gets a lot of action, like if it’s used very frequently by a lot of swimmers, after prolonged periods of sun or rain, or when the water or chlorine level changes significantly (for the latter, whenever it goes below three PPM). It’s also best to do it after you open it up after a long time of not using it and before you cover it up for the off-season. Don’t wait until your pool water gets cloudy or if you see algae build up. By that time, your pool will require more cleaning than just a simple pool shock.

Shocking a pool is better done at night because sunlight can decrease the effectiveness of the process. Plus, while the work only really takes an hour to do, you’ll have to leave it in the chemical for up to eight hours, so it makes more sense to leave it at night when the pool’s not in use.

If you have any more questions about shocking a pool, or just want advice on better pool (and hot tub!) maintenance, check out Pool Care Guy for everything you need to know.