LSI, part 3- Practical tips

In Blog, Chemistry, Maintenance Tips by Kate Cunha

Welcome to the 3rd and final installment on my chat on LSI. If you’re reading this, thank you for sticking with me!


Let’s talk about some practical steps that you can take to make balancing your pool to LSI a bit easier. First and foremost, test your fill water. Yes, you read that right. Start with running a full battery of tests on your fill water. You want to know exactly what’s coming through those pipes before the water hits your pool. Why? Because your fill water is your baseline and directly affects how you will need to balance your pool water. By knowing what your fill water brings (or doesn’t), you’ll have a heads up on your pool’s needs, which can help you plan your maintenance routine and can even help you make decisions about which types of chemicals are most appropriate for your facility.


For example, let’s say you’ve tested your fill water and find that it has a TA of 30. That means that your pool with nothing but fresh water will start with a TA of 30 and that you will need to add enough Sodium Bicarbonate (baking soda) to raise the TA to an optimum 100ppm. That also means that each time you partially drain and refill, or even just top up after normal backwash and splash out loss, your TA will take a hit. By knowing that your fill water has a low TA, you’ll expect that and can be prepared, saving you time and money in labor hours.


As I mentioned above, knowing your fill water can also help you choose chemicals that will make balancing to LSI easier. If you use chlorine with a high pH, your choice for pH control is muriatic acid or CO2. Acid reduces total alkalinity, whereas CO2 has the tendency to raise it. So for a pool with a naturally low TA, CO2 would be a smart choice when it comes to balancing to LSI. Why not let your pH control medium work for you and make your job just a bit easier?


Your choice of chlorine can also make balancing to LSI easier if you base your choice on your fill water. Some areas of the country have rather hard water, meaning the fill water of a pool there could have naturally high calcium hardness. I have personal experience with a pool that routinely had a CH of 600-800, no matter what they did. Using Calcium Hypochlorite to chlorinate that pool would be foolish, since CalHypo will raise the level of the calcium hardness over time. But CalHypo can be rather useful in a pool with a naturally low CH. It’s all about finding the balance that works for your pool.


There is a bit of a shortcut that can turn all of these last 3 blogs into simple steps to help you stay ahead of water balance. Choose one day each week when you will test and balance the water. Every week, bring your calcium hardness to as close to 250 as possible, then set your total alkalinity to 100. If you are using a chemistry controller your pH should be stable (we like to see our clients set theirs at 7.4, for enhanced efficacy of the chlorine). If you do not use a chemistry controller, then your final step is to adjust your pH, and you are done! These 3 levels will bring most water into the balanced range on the LSI chart, even accounting for differences in temperature and total dissolved solids.


Due to the very nature of pool water, and its use, balancing water is not linear. Rather, it’s an organic process and should be approached in that manner. Hopefully these tips help you stay ahead of curve when it comes to the LSI balance of your pool.