A pool pump serves several purposes. It removes water from the pool, sends it through the filter to be cleaned and in the case of a saltwater pool, runs it through the salt chlorinator which converts salt to chlorine to sanitize the water. It then returns the water to the pool and the cycle continues as long as the pump is running.
Salt chlorinator manufacturers tend to recommend running your pool pump 8 hours per day and they tend to suggest that you do so during the hottest part of the day when the sun is up. UV rays from sunlight kills chlorine as does contaminants brought into the pool typically by people swimming in the pool, debris falling into the pool and from rainfall. Adequate chlorine can only be produced by a saltwater chlorinator when the pump is running for a reasonable amount of time.
More specifically, your chlorinator manufacturer will most likely tell you to run the pump long enough each day that all water in the pool passes through the pump each day. So if you have an 18,000 gallon pool, you want all 18,000 gallons pumped each day. You can figure this out by determining how many gallons per hour (GPH) your pump processes and dividing that by the pool size. So an 18,000 gallon pool using a Hayward SuperPump capable of pumping 3,660 gallons of water per hour means you need to run your pump 18,000/3,660 = 5 hours per day. So 8 hours of pump time should be more than enough in this instance.
But even when the pump is running, the chlorinator might not actually be active. Modern chlorinator systems can be set from 0% – 100% of pump operating time and only produce chlorine when the pump is running.
The % settings relates to the amount of time the pump is set to run each day. So if you set the chlorinator to 50% and run your pump for 8 hours per day, the chlorinator will operate for 50% of that time, or 4 hours. When the pump shuts off, chlorine production stops. But the pump can run and the chlorine production remains off when the system has reached its setting limit.
It’s generally recommended to start your salt chlorinator system at 50% setting and adjust up or down if necessary. Assuming salt and other pool chemistry is within range, you would turn the setting % up to produce more chlorine and reduce the setting % to produce less chlorine. In the hot part of the summer with heavier pool usage, you might adjust the setting upwards and in the cooler periods with less pool usage the chlorinator setting might be reduced. If you manually check your chlorine levels with test strips, check once per week or more if needed to ensure your pool settings are adequate.
As temperature drops, less chlorine is required to keep a pool sanitary and clean for swimming. Here is a line from Hayward who manufacture pool pumps, chlorination systems and other equipment. This relates to the % setting of the chlorinator system and how the system adjusts down chlorine production as temperature drops:
Output is scaled back to 20% of the desired output setting at 60° F. Chlorine production stops at 50° F.Hayward AquaRite user manual
So as temperatures drop to 60° chlorine output automatically drops too because not as much chlorine is required to keep the pool sanitized. When the temperatures drops to 50° chlorine productions stops completely because at this low temperature, the salt cell can be damaged, the pool requires little chlorine at this point, and salt generally doesn’t convert well to chlorine at this temperature.
Modern chlorinator systems take temperature into account to avoid over chlorinating a pool which can over time damage equipment, lead to the premature end of a salt cell and having to replace it. In the immediate term, an overly chlorinated pool can also irritate eyes and skin, which are two things that you shouldn’t get in a salt water pool when chlorine levels are within range.
Salt Levels And Chlorine Production
It’s important to maintain a reasonable level of salt in your saltwater pool to ensure adequate chlorine production. Too little salt means the system won’t be able to produce enough chlorine and the water will become cloudy and eventually algae will grow. Too much salt can damage pool equipment and cause other negative side effects.
Modern salt chlorinator systems have a built in feature that detects high salt levels and will warn you so that you can address the situation. They may also automatically shut down if salt levels are too low. Again, a range of 2,700 ppm – 3,400 ppm salt content is ideal for a saltwater pool.
Adjusting Salt Levels Up and Down
Low salt level: If your salt level is too low, you can use a salt calculator like this one to determine how much salt to add to bring the system up to the desired range. You type in your pool size in gallons, your current salt level, desired salt level, hit Calculate and then scroll down to see how much salt to add. You simply pour that amount of salt directly into the deep end of the pool and allow it to dissolve. Some salt systems will shut off when salt is too low to protect the system which means no chlorine will be produced until salt levels are raised.
High salt level: If the salt level is very high (ie. 4,000 ppm or greater) you may have to drain water to bring the salt level down, and top the pool up with fresh water (ie. unsalted tap water) to dilute it further. A rule of thumb is that draining 1 inch of water from your pool removes 100 ppm of salt from the pool. It might take a day with the pump running for the salt level to reach its desired range again.
The 2,700 – 3,400 ppm range is quite a wide range for salt content and it can fluctuate during the pool season. More pool use + more hot sun + more rain = more chlorine needed which increases the salt usage. Salt needs to be replaced over time as it basically wears out.
Suggestion: Keeping your salt level on the high side – closer to 3,400 ppm than 2,700 ppm – means that your salt cell doesn’t have to work so hard as there is more salt available to use. It’s cheaper to buy more salt than it is to buy a new salt cell.
If the salt level is 3,500 ppm or so and you’re early in the pool season, I’m not sure I’d do anything. Chances are you’ll be adding water soon due to evaporation and splash loss and the salt level will drop as a result.
A quick and dirty rule of thumb is to run your pool pump for 8 hours per day during the season to filter the water and produce enough chlorine to keep the pool sanitary. Of course, when the pump is off, no chlorine is being produced so the more you run the pump the more chlorine will be produced.
You can increase chlorine production by increasing the chlorine setting on your pool chlorinator or by increasing pump time per day. Or by doing both. If you find that chlorine levels are low, increase the % setting on your chlorinator. Throughout the season, you might find that you need to turn the % setting UP during hot periods and heavy pool usage and then adjust the % setting DOWN later in the season when it’s not as hot as the pool is no longer being used.