First check your Salt Chlorine Generator Owner's Manual to determine what level of salt your Salt Chlorine Generator operates at. They generally operate at target levels between 3000 to 4000 ppm. For this example we will assume that your Salt Chlorine Generator operates at 3500 ppm. So, you will want to add enough salt to your pool to bring the salt concentration level to 3500 ppm.
Your next step is to determine the current level of salt in your pool. If you have just installed a new pool, your salt level will be 0 ppm. If you have an older pool and are converting from a standard chlorinator, your pool will have a low level of salt concentration, typically around 500 ppm. .
Measure your pool's current level using a Salt Water Test Strip. Assuming you have an older pool, your reading will be around 2.0. The table on the back of the test strip container converts the reading of 2.0 to a salt level of 500 ppm. If you have a pool store nearby, we would also recommend taking a water sample to them to verify your measured salt level. This service is generally free and more accurate.
To determine how many pounds of salt you will need to bring your salt level to 3500 ppm, calculate the number of gallons in your pool and add salt according to the Salt Table. For our example, if your pool has 10,000 gallons of water and your current salt level is 500, you need to add 250 lbs of salt. If you don't know the number of gallons in your pool, see the first steps of How to Size a Pool Pump for instructions.
Salt is typically packaged in 40-pound bags. So in our example, if you have to add 250 pounds of salt you will need to add about six bags. Use a salt that is at least 99.8% pure sodium chloride (NaCl). The preferred salt is an evaporated, granulated, food quality, NON-iodized salt. Avoid using salt with anti-caking agents like sodium ferrocyanide, also known as Yellow Prussiate of Soda (YPS). These cause some discoloration of fittings and pool surface finishes. DO NOT use calcium chloride.
Before adding salt to your pool, be sure to TURN OFF the Salt Chlorine Generator at the Control Unit. The generator should not be turned on until the salt has completely dissolved. Leave the PUMP ON to circulate the water and help dissolve the salt.
After the salt has dissolved, turn on the salt chlorinator. Check to see that the salt level is around 3500 ppm. Your pool should be maintained at around this level. A low salt level (below 3000 ppm) reduces the efficiency of the salt generator which results in low chlorine production. A high salt level (above 4500 ppm) can rapidly reduce the life of the cell.
A word of advice: if you think you need six bags according to your calculations, only add five bags at first. Let it dissolve and retest your salt level before adding your last bag. It's a lot easier to add another bag, if required, than to have to reduce the salt level if you've overshot your target salt level. If you do end up with too much salt in your pool, see our guide, How To Reduce the Salt Level In Your Pool, for instructions.