Simplify Pool Chemistry

This is a guest post by Eric Knight with Orenda Technologies.

Commercial swimming pools require a lot of maintenance and day-to-day monitoring. The good ones have chemical automation systems, quality filtration and circulation systems, and secondary sanitization systems like UV or Ozone. There are many moving parts, and to a swimming pool operator, it can seem overwhelming. I know, because I was once a commercial pool operator myself. It was daunting.

When it comes to pool chemistry, we can subdivide the topic into two categories: sanitization, and water balance.


Sanitization, in my opinion, is the easy part. This is keeping the water clean, safe, and sanitized. For most commercial pools, this is primarily accomplished with chlorination. Chlorine residuals are maintained by staying ahead of what is called the breakpoint”, where combined chlorine is destroyed to a point where it can no longer be reduced. Provided water maintains a healthy free chlorine residual, it should be safe to swim in.  At least, in theory.

In reality, there are many other demands put on chlorine. In other words, we rely on chlorine to do more things than it was designed for. Chlorine is an outstanding sanitizer/disinfectant. But most of it gets used up oxidizing non-living bather waste. Compared to its strength as a germ killer, chlorine is a relatively weak and inefficient oxidizer. It gets bogged down, which can lead to cloudy water, higher levels of combined chlorine, and more chlorine consumption.

Another important aspect of sanitization is preventing outbreaks in the first place. Elements like phosphorus (in the form of phosphates in water) are nutrients for algae and other microorganisms. Without removing phosphates, your water is relying on killing reproducing generations of algae and other nasties. When the reproduction/growth rate of the contaminant exceeds the killing rate of your chlorine + secondary sanitizers, you will have an outbreak.

Proactive Chlorine Supplementation

CV-600 Enzyme on Feeder

We can simplify and optimize sanitization by supplementing chlorine. We recommend supplementing it in two ways. First is the use of enzymes that break down and remove non-living organic waste (bather waste). This relieves chlorine of its massive burden to oxidize the bather load. With enzymes, less chlorine is needed to conquer the demand, and therefore more chlorine is available as a residual to disinfect the water.

Second, we recommend removing phosphates regularly. Removing phosphates reduces the nutrients available for reproduction of algae and other living contaminants. It won’t kill anything, but it will slow the growth. When done right, the growth/reproduction rate will remain slower than the killing rate of chlorine, which prevents outbreaks.

Both strategies use simple, NSF-50 Certified chemicals to supplement chlorine.


Orenda’s free mobile app calculates LSI for you.

Outside of sanitization, the rest of water chemistry is about balance. And when we say “balance”, we are talking about the saturation level of calcium carbonate (CaCO3). This saturation balance is measured using the Langelier Saturation Index (LSI). We built a free mobile app that calculates the LSI for you (download here on iOS or Android). The LSI takes six factors into account: pH, carbonate alkalinity, calcium hardness, water temperature, total dissolved solids (TDS), and cyanuric acid (CYA).

So if you’re only testing for chlorine, pH and [sometimes] alkalinity, you’re still missing half the equation! The LSI is what water cares about…not ranges of chemistry printed in a textbook.

So balance water according to the LSI, and you might be shocked at how well the water behaves. Prepare to be pleasantly surprised at how much less you spend on chemicals to keep pH and alkalinity adjusted.  Think about it.  Think of all the chemicals used in swimming pools just to manage pH and alkalinity. Acid(s), CO2, sodium bicarbonate, sodium carbonate (soda ash), etc.. Wouldn’t it be nice if those factors fluctuated less?  With an LSI-focused strategy, it can happen.

Proactive Water Balance Techniques

Embrace calcium as your friend, not your enemy. Pool operators assume calcium hardness is the primary driver of carbonate scale formation…but that’s not true. The LSI shows us that calcium hardness is far less of a factor than pH and even water temperature. Elevated levels of calcium hardness (400 ppm +) can be to your advantage! Water cannot over-saturate itself, so if you use calcium and alkalinity to create a balanced environment, pH tends to become more steady.

Stay within -0.30 to +0.30 on the LSI, and ideally 0.00 to +0.30. On the Orenda app, the ideal zone is an LSI value that is green. If you just maintain water chemistry in that zone every time you treat the water, you’re doing a great job.


I hope this article helps you simplify your pool chemistry. On the sanitization side of water chemistry, supplement chlorine with enzymes for bather waste, and phosphate remover for reducing nutrients. For water balance, learn the LSI and build your chemistry strategy around it.

Eric Knight is a former competitive swimmer that developed asthma from swimming indoors. He is in the aquatics industry primarily to fix indoor air quality problems in natatoriums, and currently works for Orenda Technologies.


If this brought up any questions, or if there’s anything you’d like to read, learn or hear more about, visit our contact page or drop us a line at Subscribe to our emails in the upper right hand corner to get this information sent directly to your inbox as well. 

Improving Your Natatorium’s Environment: Creating Healthy IAQ

Tags: , ,

When you go to an indoor pool, what do you first notice? We often first feel the warmth and humidity, and then smell something that resembles a strong chlorine odor — although it’s not actually chlorine. Actually caused by chloramines (combined chlorines) off gassing from the pool’s water surface, this odor is the by-product from chlorine disinfecting the water of dirt and organic material, and is a sign that the pool’s indoor air quality (IAQ) is struggling. As these pollutants are unhealthy to breathe in and are corrosive to metal in the facility, poor natatorium IAQ poses both health and operational consequences. 

Healthy Indoor Air Quality (IAQ) Matters

Your natatorium’s environment is a key aspect of having a safe and efficiently-operating aquatic facility. Designing the natatorium experience for people visiting, swimming and working at your facility is of the utmost importance; think of children taking swim lessons, the swim instructors, swim teams competing for an entire day and the lifeguards that watch over during that time.  Maintaining great IAQ is a balancing act, and no single system or product will give you that alone; it takes an integrated approach where the elements of your air and water systems work together.  

When designing a natatorium, the relative humidity, air temperature, pool water temperature, pool activity levels, air distribution, outdoor air, exhaust air and pool water treatment are all key aspects that must be addressed to provide a good environment. At Pure Water Aquatics we focus on integrating these elements to create the healthiest, most long-lasting indoor pool for all parties — the owners and operators, swimmers and spectators. In this article we cover a few main elements that contribute to healthy IAQ for your natatorium environment, and what to consider when designing your HVAC system for your natatorium environment. 

There are many factors impacting Indoor Air Quality, but in this article we will be covering these two key factors that have a direct impact on IAQ: 

  • Pool water chemistry 
  • Poor air distribution

Pool Water Chemistry

By maintaining optimal pool water conditions you will have the best possible indoor air quality and ensure optimal performance from the mechanical system. Ultraviolet light (UV) treatment of pool water has shown to have a very positive impact on the water chemistry and can help reduce waterborne chloramines. However, it is important to note that UV cannot remove chloramines that are already airborne. This is why it is important that different parts of your total system work together.

Remember that strong odor caused by chloramines we spoke about in the beginning? To avoid chloramines, it is imperative to maintain proper free chlorine and pH levels. Test your water regularly for chlorine, pH, calcium hardness, phosphates and total alkalinity.

Jacob James, Energy Engineer and certified Energy Manager, writes, “Building controls can now seamlessly connect and optimize the vast majority of natatorium equipment. For example, a UV system can now increase or decrease its output (dosage) as directed by the chemical controller, a relatively new capability in the marketplace.”

Additionally, we’ve worked with aquatic facilities to integrate controls that were once operating independently from each other. This helps the system you have in place to become more efficient, saving you time and money. Jacob adds, “Integrating these new control systems presents significant opportunity to improve building performance. In fact, natatoriums that have installed system-wide controls systems have seen their operating costs go down while creating a healthier space for their pool patrons.”

Pool Air Distribution

The proper balance of outdoor air, room exhaust air, and air movement at the water surface is crucial to ensuring chemical concentration levels are maintained within acceptable levels. To minimize evaporation and balance air movement at the water surface, your HVAC system should be configured to pull air across pool water surfaces.

Additionally, ASHRAE calls for maintaining the natatorium air temperature at two to four degrees above the pool water temperature and not above 86 degrees F. By doing so we’re trying to balance HVAC equipment size and the energy costs of maintaining conditions in both natatorium and water. 

ASHRAE also recommends the relative humidity in a natatorium be maintained between 50% – 60% relative humidity. Lower relative humidity increases operation costs because of increased evaporation, while also causing swimmer discomfort due to evaporative cooling from their bodies when they get out of the pool. However, the higher the relative humidity is, the greater the risk to the building structure.

The Elemental Approach

We understand that maintaining healthy IAQ can feel anywhere from frustrating to downright overwhelming and stressful, but it doesn’t have to be that way. Excellent IAQ is a key building block of our Elemental Approach, where we analyze your facility’s overall natatorium environment by breaking it down into small elements. Healthy air quality is just as important as clear water, and with our Elemental Approach, we do a deep dive into all of the tools and processes your facility uses to contribute to your IAQ and clear water. From there we create customized solutions specific to your pool’s operating system and design. 

When designing and managing your HVAC system, proper commissioning and taking into account the many factors of IAQ will help create a sustainable and efficient operating system for your natatorium environment. We will be covering more of these factors — including outdoor air ventilation, exhaust air, air change rate — and commissioning, in our upcoming blog posts as a part of this series well.


This article is the beginning of an ongoing series for enhancing your natatorium space. If this brought up any questions, or if there’s anything you’d like to read, learn or hear more about, visit our contact page or drop us a line at Subscribe to our emails in the upper right hand corner to get this information sent directly to your inbox as well. 

Winterizing Your Aquatic Facility

The leaves are changing, crisp air and rain are in the forecast — here in the Northwest, fall is officially here. And with that, the end of outdoor swimming season. As temperatures drop, you’re faced with the task of winterizing your inground pool in order to protect your facility’s aquatic equipment, interior finishes and tile, plumbing and more. It can feel like a lot to undertake, but breaking it down into steps with proper care can help minimize damage and the headaches that severe winter weather can create for aquatic facility managers. We’ve got some crucial and well-informed pointers from our friends at Pool & Hot Tub Alliance below. 

Another important thing to remember is that you don’t have to go this alone. If you have any questions or concerns about your facility as you’re winterizing it, speak with one of our trained consultants by giving us a call at (877) 828-0072 or

Water Treatment

As a starting point, most winterizing processes recommend balancing the pool water to PHTA standards. (See table below.) Consideration should be given to the fact that as the water temperature decreases the Langelier Saturation Index (LSI) will decrease (water will become more corrosive). This balancing process should take place 3-7 days prior to closing the pool. These levels should be adjusted and then rechecked using proper testing equipment.

Parameter Min  Max Ideal Range
pH 7.2 7.8 7.4-7.6
Total Alkalinity, ppm 60 180 80-120
Calcium hardness, ppm 150 1000 200-400
LSI -0.3 +0.5 0.0 to +0.5

At initial closing, it may be preferable to balance the water in a positive range allowing for the fact that as the temperature drops the LSI will drift downward. For chlorine and bromine pools, the pool water should be shocked using a chlorine product to remove residual swimmer waste, kill bacteria and algae, and remove other organic contaminants from the water. Additional oxidation may be performed with a non-chlorine oxidizer. The chlorine and other oxidizer residuals should be allowed to decline prior to adding additional closing chemicals such as algaecides and sequestering agents that may be degraded by high levels of oxidizer.

For PHMB (biguanide) sanitized pools, the pool water should be oxidized with hydrogen peroxide.

The use of an EPA registered algaecide is recommended due to the lack of winter filtration and the use of certain types of covers which may allow sunlight and fine organic debris and contaminants to enter the pool’s water.

Balancing the water is the first step in preventing staining to interior finishes; however, the use of an appropriate stain preventative is recommended in many regions of the United States due to the length of time the pool is shut down. Many commercially available winterizing kits will often contain sequestering or chelating agents. Always check with the individual manufacturer of the winterizing kit as to the best practice for use during the pool closing process.

Clean the pool. This should include a thorough brushing of all the surfaces, including, but not limited to walls, coves, and floor. Skim the pool’s surface and remove any floating leaves and other organic debris. Vacuum the pool.

After taking care of the water treatment, the following procedures should be performed. The topics here are not listed in the order that they should be performed. The order will vary depending on the location and type of equipment used.

Filtration Equipment, Pumps, Heaters, and Chemical Feeders & Controllers

Clean the filter. Backwash several times if a sand or DE type filter. If a cartridge filter, then remove and clean the cartridge(s), allow them to dry and then store for the winter in a warm dry indoor location. DE grids can also be cleaned, removed, and stored indoors. Empty all chemical feeders (please see precautions below). Drain your pump, filter, heater, and chlorinating equipment. Place the drain plugs in the hair and lint (pump) basket, so that you can find them in the spring.

This pool has been properly closed and ready for winter.

Purge any remaining water from the pump, heater, heat pumps, chemical feeder and other wetted equipment. Care must be taken to use the proper procedures and equipment (e.g. wet/dry shop vacuum, low pressure air compressor, etc.) since pool equipment and lines cannot take excessive pressure and overpressure could present a safety hazard. This process should only be performed by an appropriately trained professional familiar with the potential hazards associated with pressurized air.

Make sure the electrical power to any heaters or heat pumps is disconnected and the circuit breakers are in the “off” position. Turn off the pilot flame, main gas valve and gas supply to the gas heater. Drain any water from the heat exchanger in accordance with the manufacturer’s directions.

Make sure the circuit breakers are in the “off” position. In severe snow areas, the motors should be removed from the pump housing and stored indoors in a dry location. If a motor is left outdoors, make sure it has a weatherproof protective cover.

If the pool has an electrolytic chlorine generator, make sure there is no standing water in the cell. Remove the cell and store indoors. If the pool utilizes Automated Controllers and Chemical Feed Equipment, be sure the electrical power to the controller is disconnected. Remove any sensors from the flow cells then, clean and store them in accordance with the manufacturer’s instructions. Empty the flow cells then, clean and allow them to dry before storage.

If peristaltic pumps are used, remove any feed and injection tubes then clean and allow to dry before storage. Store any chemicals in accordance with state and local codes.

Automatic controllers that are installed outdoors should be removed and store indoors or protected from the extreme effects of winter.

Many pump, filter, and heater equipment manufacturers have specific instructions for safeguarding their equipment. Always check with the respective manufacturer if you have any questions.


The main damage to plumbing lines occurs from the freezing of water in these lines. By using an air compressor or the discharge side of a shop vacuum, you should purge the water by blowing air through the lines until bubbles appear inside the pool. This includes all return lines, suction lines (skimmer and main drain) and lines to water features, solar heating, pool cleaners, and slides. Again, caution is advised on the use of pressurized air. On return lines, you will want to remove the wall fittings and insert tapered expandable plugs once the lines are clear of water. Tighten in place. In some locations, severe freezing water may dictate the use of straight pressure plugs.

Suction outlet (main drain) lines should have air blown through them until bubbles appear in the pool then plug the pipe topside or close the valve to the suction outlet. The idea is that you will create an “air lock” in the line preventing water from re-entering the lines.

Skimmer lines must be purged with air and then once bubbles appear screw in a threaded expansion plug into the skimmer. These devices will prevent freezing water from expanding and cracking the skimmer. Use an appropriate (e.g. PTFE) plumbing tape on the threaded fitting to insure a water-tight seal.

Lowering the Water Level

The issue of draining water from the pool and the amount is often based on regional differences and the type of cover (solid or mesh) used on the pool. Issues such as the amount of rain, snow, and snow melt will often influence the amount of water drained. It is always prudent to consult with your winter cover manufacturer as to the proper amount of water to be drained to avoid damaging the cover. In addition, one must take into consideration the fact that freezing pool surface water can damage waterline tiles, prematurely dry out vinyl liners, and expose plaster surfaces to the atmosphere which can create cracking and defined water line indications on the surface.


Prior to installing winter covers, ladders, diving boards, and handrails should be removed, cleaned and then stored in a dry place.

On all covers, leaves and other organic debris must be periodically removed to prevent plugging the cover pump or damaging the cover.

Tracked solid covers must be monitored for accumulation of water, snow, and ice. Excess weight from these items can damage the track system, possibly damaging the concrete, coping or pool wall.

With all winterizing covers, the long term durability and longevity of the cover is dependent on proper water balance, proper water levels under the cover, regular maintenance and cleaning.

Safety covers keep your pool protected from accidental entry and help prevent dirt, debris and leaves from entering during the winter months. We also love them for their durability.


Winterizing or closing should occur before the first hard freeze. Make sure to  consult with the various chemical manufacturers, pool manufacturer or builder, equipment manufacturers, and cover manufacturers for the correct procedures and processes to use for where your climate.


If there’s anything you’d like to read, learn or hear more about, visit our contact page or drop us a line at and subscribe to our emails in the upper right hand corner.