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SRK Custom Water Systems VS Alternatives

Both consumers and fellow professionals often ask me what’s so special about the SRK HydroZone 3 treatment system? It’s a valid question. After all, the market is flush with chemistry solutions that claim they are the best way to treat pool and spa water. What differentiates HydroZone 3 water from other solutions?

For starters, HydroZone 3 is a composite of systems that impact the entire operation of the pool. Chemistry is a big part of it, but it is only part. Proper filtration, balanced hydraulic design, distribution throughout the entire pool, and other factors all play a role in creating HydroZone 3 water.

For the sake of comparison, however, let’s look at just the chemical side of HydroZone 3, which is an outgrowth of our treatment philosophy at SRK Pool Services. It combines ozone, ultraviolet (UV), and small amounts of chlorine. The main reason we combine these methods is that we’ve found when used together, the whole is greater than the sum of the parts. All three measures hold hands and make the others stronger.

That treatment synergy is hard to explain but is arguably the main reason HydroZone 3 is so effective; it covers all the major aspects of water treatment in a highly efficient and effective treatment program.

Together & Alone

The first set of comparisons is how HydroZone 3 stacks up against systems that rely solely on ozone, UV, or chlorine.


More well-known as a crucial gas layer in Earth’s atmosphere, ozone is the most powerful disinfectant and oxidizer available for swimming pool and spa water treatment. It is extremely effective in killing algae and pathogens, including the infamous Cryptosporidium, which is notoriously resistant to chlorination. Ozone also readily oxidizes organic compounds that feed bacteria and algae.

By itself, however, ozone does not provide a lasting residual chemical concentration. It only stays dissolved in water for about 18 minutes before dissipating. Systems using only ozone basically have to run 24/7 to provide constant disinfect and oxidation. That means someone swimming in the water when the system is not operating could be exposed to some form of infection. If ozone is run all the time, it has the opposite problem of building up to levels where it off-gases from the water, which is both toxic and prohibited by law.

UV Sterilization

Once used primarily in ponds and aquariums, UV systems have become popular in pools and spas because they are very effective at controlling bacteria. Rather than disintegrating unwanted organisms the way ozone and chlorine do, UV scrambles their DNA so they can’t reproduce. That relieves the sanitizing burden from both the ozone and chlorine in HydroZone 3 water, making all three more efficient. In addition, ozone helps clarify water, which in turn enables UV to better penetrate the water and work more effectively.

Also, when combined with ozone, UV generates hydroxyl radicals by a process known as the advanced oxidation process (AOP). Hydroxyl radicals are incredibly powerful oxidizers, but only last for a fraction of a second. They add an amazing quality to the water when the systems are running.

However, in pools and spas, UV should never be used as a stand-alone treatment method. It adds no chemicals to the water, therefore providing no chemical residual, and it does not oxidize organic compounds.


The tried and true method of pool and spa water treatment, chlorine plays only a bit role in generating HydroZone 3 water. We use a chlorine feeder to add a tiny 0.3 parts per million (ppm) residual that is there strictly to protect bathers from bacteria from other bathers when the system is not running. Because of the sanitizing action of ozone and UV systems, the chlorine does not do most of the work and is there mostly as a secondary layer of treatment.

On its own, chlorine is a very effective disinfectant and oxidizer. It also has the ability to stay in solution providing a lasting chemical residual. That is why it’s been such an enduring treatment method.

The problem with chlorine is that as it does its work, it produces disinfection by-products, chiefly chloramines, but others as well. When these disinfection by-products (DBPs) accumulate, water quality deteriorates. DBPs cause the familiar chlorine smell, eye and skin irritation, and can lead to respiratory issues in more extreme situations. The DBPs make the water cloudy and unappealing.

This is why so many consumers have been turned off to chlorine. It’s also the reason we use it only sparingly in HydroZone 3 water. At our low residuals, chlorine is able to disinfect and oxidize without forming by-products in concentrations that impact water quality.

Other Comparisons

A handful of other popular treatment methods offer advantages and disadvantages compared to HydroZone 3.

Saltwater Chlorine Generation (SWGs)

So-called “saltwater pools” have become extremely popular over the past 20 years and for some good reasons. Mainly, these systems use salt dissolved in the water to generate chlorine by way of an electrolytic process, similar to how it’s done in a chlorine factory but only on a much smaller scale. This means you don’t have to buy, transport, or store chlorine. Because SWGs generate free available chlorine, they offer the disinfection and oxidizing power of other chlorinated pools.

However, SWGs are notorious for driving up pH and alkalinity, creating significant problems maintaining water balance. HydroZone 3 water is always balanced because the treatment method has almost zero effect on pH or alkalinity. Also, saltwater is extremely corrosive and will damage metal pool fixtures, such as rails, ladders, and light rings as well as stainless steel components in some filters. HydroZone 3 water is not corrosive.

Metal Ionizers

Far less popular than most other treatment methods, ionizers release copper and silver ions into water to kill bacteria and algae. It’s not a new idea as the Romans first used silver plates in their bathes to help purify the water. In fact, ionizers can kill most common pathogens and inhibit algae.

Ionizers do not oxidize organic compounds and, therefore, cannot be used as a stand-alone system. Most are typically used in conjunction with some form of chlorine. They also can lead to staining when the silver and copper compounds precipitate out of solution.

AOP Generators

Earlier, I mentioned how ozone combined with UV generates AOP, and I do believe there are significant benefits as a result, including an elusive water quality that feels somehow vibrant and soothing at the same time. There are now dedicated AOP systems that generate hydroxyl radicals, which do kill bacteria and oxidize organics.

One problem with AOP is that hydroxyl radicals are so short-lived they can’t even be measured, meaning their very existence is mostly theoretical. And, there is very little existing science about how well they work in recreational or public water. We hopefully will know more at a later date, but as it stands today, AOP is a largely unknown entity.

the Water Geek


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A blog about all things water, written by SRK's founder Steve Kenny.