Chlorine Demand & Your Salt Chlorine Generator

We receive inquiries from customers on a consistent basis reporting that their pool has little to no chlorine. In many of these cases there is not a equipment related issue at play instead it could be a water chemistry issue even when a water test shows well balanced normal water conditions. If your Pool Pilot is showing an error code you will want to refer to our equipment troubleshooting guide or contact our technical support.

There are several situations in which you may not be able to read a chlorine level in the pool, yet there are no error displays on the AutoPilot. Some are Operational and some are from Chemical Reactions. A quick test is to place the units in BOOST mode, wait 30 seconds, loosen the lower cell union, and then take a water sample after the cell. Test for chlorine, which should yield a higher level than what’s in the pool.

Chlorine Demand

Chlorine demand is the amount of chlorine needed to treat all of the contaminants in pool water. Some pools have extremely high chlorine demand while others have normal or even low chlorine demand. You could have a perfectly working salt chlorine generator running at peak efficiency combined with a increased or high chlorine demand and still yield little to no chlorine. Sunlight (UV) exposure, inclement weather, slides, pool parties and water features are all factors that can cause increased chlorine demand.

Cell Too Small
If the salt cell being used is undersized for your pool and its chlorine demand your Pool Pilot system will not be able to create enough chlorine to meet the demand. Borderline sizing, that is, if you have a 20,000 gallon pool, do not install and 20,000 gallon rated cell, will probably not provide enough chlorine. Contact us to learn if your Pool Pilot controller can accommodate a larger sized cell.

Pump Run Time Insufficient
Similar to undersized cells, you must run the pump long enough to be able to generate sufficient levels of chlorine daily. Upsizing the cell will allow you to lower your pump run time.

Stabilizer
Stabilizer is the most common chlorine demand issue that we deal with. Maintaining proper stabilizer levels ensures that your chlorine is protected from UV rays of the sun. Not maintaining proper stabilizer levels ensures that the sun will rapidly degrade the chlorine being produced by your salt pool chlorine generator. For residential pools the stabilizer level should be maintained at 60 – 80 ppm. Even at a median 30 – 40 ppm your pool will have somewhat rapid chlorine loss especially during the peak of summer.

Phosphates
The industry is still learning about phosphates and at what points they can cause issues with chlorine levels. Ideally you will have a phosphate level of 0 ppb. When troubleshooting chlorine demand issues we recommend treating any phosphate level about xxx ppb. Phosphates serve as a food source for algae. Phosphates are introduced to pool water by lawn fertilizer, laundry detergents, some household cleaning bleaches & tile/vinyl cleaning agents. Some pool owners living near agricultural areas or golf courses have had phosphate levels via airborne sources. A chemical treatment is needed to eliminate phosphates when found in pool water.

Sodium Bromide
Unfountantley another common issue that can create high chlorine demand is the something that pool stores will sometimes sell to pool owners to fix algae problems. Many pool stores market “yellow” or “mustard” algae removal products containing SODIUM BROMIDE. Although the clerk at the pool store or even the package the treatment comes in advertises it as being “salt pool compatible” it can cause extreme issues in relation to your chlorine levels. Every year we troubleshoot dozens of pools with issues caused by the addition of sodium bromide.

To remedy the addition of sodium bromide:
Turn the AutoPilot Pool Pilot controller down to 0% output. Add Sodium Hypochlorite manually, daily, to maintain 5 ppm or higher until you’re able to maintain a chlorine residual overnight. Determine this by testing your chlorine at night and again in the morning. Expect the chlorine level to be lower in the morning, due to the reaction of the sodium bromide. Add your chlorine after your morning test. Once you’re able to maintain the chlorine residual, you can turn the AutoPilot back on.

Usage (“Bather Load”)
For residential pools the usage (known in the industry as “bather load”) is a less common issue in relation to chlorine demand although it is certainly something to take in to consideration. On commercial and public pools however it is one of the most important things to factor when looking at chlorine demand.

An active adult swimmer can lose a pint or more of perspiration in a hours time.

  • Sunny conditions
  • Hot water
  • Nitrates
  • Sodium bromide
  • Other contaminants