Pool Chemistry Start Up
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This page is for pool owners who are just filling their swimming pool for the first time, as well as existing swimming pools who are starting over with a fresh fill of water. Many pool owners are confused about which chemicals they need to adjust as well as the order they need to be adjusted in during a fresh fill and start up of a pool. It is important to note that this information is of the general variety and every swimming pool can be unique in terms of the chemical balance. The quality and initial chemical balance of your fill water will have a lot to do with what (and how many) chemical you need to add to get your pool started.
Before you begin adding anything to your pool it would be a very smart idea to have the water tested first. You need to know the numerical values for things like pH, total alkalinity, calcium hardness, salinity etc. before you can start to make corrections. This means that learning how to test your water is very important. You can do this from home with a quality water test kit like a Taylor Technologies K2006 Complete test kit. Alternatively you can also bring your water sample to a local pool and spa store for a detailed (and usually free) water test. It is important to know what the current values in the water are before you start adding any other chemicals. Adding chemicals to a pool should never be a guessing game. You should only ever add chemicals that you know are needed and in the volumes required to meet the chemistry needs of your pool. Let's look at this a little closer.
Total alkalinity - 80 to 120 ppm
pH - 7.2 to 7.8
Free chlorine - 2 ppm to 4 ppm
Total chlorine - equal to free chlorine
Combined chlorine - should be zero. Never more than 1 ppm
Calcium hardness - 200 to 400 ppm
Cyanuric acid - 30 to 50 ppm
Total dissolved solids - Under 2500 ppm (higher for salt pools)
Sodium level - not important for chlorine pools. Important for pools that will be salt chlorinated
Phosphates - under 500 ppb
Iron - 0.00 ppm
Copper - 0.00 ppm
Order of chemicals - When you are filling your pool you can start by testing the fill water for the values listed above. This will be a good starting point to let you know the quality of the water you are starting with. The order of corrections for the water are generally in the same order that you see them listed above. Since you should not correct all of your chemicals at the same time, but instead leave multiple hours in between making corrections before adding other chemicals, it will take you on average one to two days to get each of the chemicals within balance. The one "out of order" chemical I will often add to a newly filled pool is chlorine. Without the CYA established at 30 to 50 ppm any chlorine you add will be short lived, but pools often will turn green before they are even completely full. To prevent this I tend to recommend adding some chlorine as the pool is filling or upon initial startup of the filtration system. This should be enough to stop the water from turning green while you are adjusting the rest of your water chemistry values.
How much of each chemical do you add? - You need to know the approximate volume of your pool. Next you can google or read the instructions on the chemicals you are using. All pool chemicals will tell you on the label how much you need to raise the parts per million based on a volume of water like 10,000 gallons. For example, 1.5 lbs. of baking soda will increase alkalinity by about 10 ppm in 10,000 gallons. So if you have a 25,000 gallon pool and you need to raise alkalinity by 30 ppm you would need 4.5 lbs x 2.5 = 11.25 lbs of baking soda to increase a 25k gallon pool by 30 ppm. Commonly when making larger chemical corrections you break up the dosing into two doses instead of one large one. This will help avoid overshooting and allow you to more accurately arrive at the desired ppm outcome.
So you test the source water, fill the pool, add some chlorine to slow down the initial algae growth and then you begin working on the list of chemistry values listed above. If you have a salt water pool you would not add salt until the rest of the chemistry values are perfect and the water looks clean and clear. At this point you add 2/3rds of the amount of salt you think you will need to reach the desired ppm value for the salt system you have (commonly 3000 ppm range). Brush the pool for 24 hours before re-testing the salt levels and adding the remainder you need to reach your desired ppm range.
Every pool is unique and you may find that many of these chemical levels are already within the correct range at start up, provided you have a high quality water fill source. Low quality water sources like rural water supplies, wells etc. should be tested (especially for metals and phosphates) before using this source to fill your pool. Trucking in water might be a lot more money than filling from a hose, but if you have a low quality water supply then almost certainly it will be an advantage to you to pay for better fill water. Using contaminated water sources like a well can really cause problems with pool chemistry, especially high iron or phosphate levels.
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Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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