Salt water pools use chlorine as a sanitizing agent to keep the pool water clean. The difference is that in a salt water pool, the chlorine is created by the chlorinator rather than being manually added in chemical form.
However, some people who are new to the concept wonder what happens if you put chemical chlorine in a salt water pool? In actuality, manually adding chemical chlorine is a normal and expected part of salt water pool ownership.
Salt water pools often need chemical chlorine manually added to boost the chlorine level quickly such as when opening the pool in the spring, after heavy rain and during hot periods in the summer when the pool is being frequently used.
Manually adding chemical chlorine can be a necessary and effective way to quickly ramp up the chlorine level when needed. Let’s take a closer look at how and when we may need to use chemical chlorine and also spend some time on the why.
After all, it’s a salt water pool so why the chlorine?
Why do you add chlorine to a salt water pool?
Swimming pools require a sanitizing agent like chlorine, bromine or ozone to clean the water and keep it safe for swimming. A salt water pool is a chlorinated pool but instead of adding chlorine weekly like other pools require, you use a salt chlorinator to produce chlorine from dissolved salt.
Dissolved salt in water on its own does nothing but when run through the chlorinator and electrically charged, it is converted to chlorine.
So you add salt to the pool to fuel the chlorinator that produces the chlorine.
But then why do you still need to add chlorine to your salt water pool if that’s the job of the chlorinator?
How a salt water pool chlorinator produces chlorine
Your pool pump sucks water from the main part of the pool and runs it through the filter to clean it and through the chlorinator to produce chlorine. When the dissolved salt in the water passes through the salt cell, a process called electrolysis converts the salt in the water into chlorine. That’s how chlorine is made.
A salt chlorinator generally produces a steady but slow stream of chlorine. When you buy the correct sized chlorinator model for your pool and local environment, it should be enough to keep the pool water properly chlorinated between 1 parts per million (ppm) and 3 ppm as required.
But salt chlorinators aren’t necessarily powerful enough to quickly move you from 0 ppm (i.e. no chlorine present in the water) to the desired range without taking a significant amount of time and putting tremendous stress on the chlorinator.
The salt cell used in your chlorinator has a lifespan in terms of the amount of chlorine it can produce. The sooner you use it up, the sooner you’ll be replacing the salt cell.
Instead you’re better off adding manual chlorine to quickly shock the pool water and bump up the level of chlorine in short order.
Why will a salt water pool show a 0 ppm chlorine reading?
You can find yourself with 0 ppm chlorine (no chlorine present) in your pool at various times such as:
- Pool opening in the spring when it was closed for the winter and no chlorine was being produced.
- When the salt cell dies and you aren’t able to replace it quickly enough before the chlorine in the water has died.
- When you experience another issue with your pool that prevents chlorine from being produced i.e. broken pump, electrical problem, water flow problem, major leak.
- After a major rain storm that requires you to drain water from the pool that has the added impact of diluting the chlorine remaining in the water.
These are some of the common reasons you may face where your chlorine is 0 or close to it.
How should you add chlorine to a salt water pool?
You can manually add chlorine or your salt water pool when required in the following ways:
- Crystal shock chlorine typically sold in small packets that are added directly to the water.
- Liquid chlorine poured into the water directly.
- Compacted and concentrated chlorine pucks that are typically put into the side skimmer to slowly dissolve.
- Crystal chlorine that is typically mixed in a bucket with water into a slurry and then carefully poured into the pool.
There are also chlorine dosing devices that automate the process but they’re generally best for chlorinated, non-salt water pools that actually require 100% of chlorine to be manually added.
How often do you add chlorine to a salt water pool?
Other than a breakdown where the chlorinator is unable to produce chlorine, you will typically find yourself adding chemical chlorine to your pool manually when you open the pool in spring and when you close it for the winter
Another common time to use chemical chlorine in your salt water pool is in the middle of the season when you get hot sunny days (direct sunlight kills chlorine) combined with heavy pool usage.
Liquid chlorine is an easy and quick way to add it during pool opening and closing since it often requires a large amount. Having some chlorine pucks or a few sachets of shock on hand for the middle of the season should be enough to keep you set in case you do require chlorine in a pinch.
For me, I needed to use chlorine pucks for several weeks when my old salt chlorinator broke and I had to wait for a new one to arrive and see installed. These days, you might be able to replace a chlorinator or salt cell quicker and avoid having to use as much chemical chlorine as I did.
Summary
Manually adding chlorine to your salt water pool is a normal thing and typically occurs when your chlorinator isn’t capable of quickly producing enough chlorine due to an event such as pool opening or closing and very hot sunny days when the pool is in heavy use.
Part of the reason people often ask if it’s normal to add chlorine to a salt water pool is the belief that a salt water pool isn’t actually a chlorinated pool. A salt water pool has chlorine but it’s mostly produced by your salt chlorinator, not manually added.
Having some chemical chlorine on hand is something you will need as a salt water pool owner. While you won’t use as much chlorine as other pool owners who don’t have a salt water chlorinator, you will need to use some from time to time as we discussed above.
