I get asked pretty frequently “what’s the big deal with combined chlorine? I know it makes the pool area smell bad but isn’t that it?”, the short answer is: No, it is not just a smell.
Combined chlorine or “chloramines” are nasty D.P.B.s (disinfection by products). They cause the irritating “chlorine smell” usually associated with pools. Chloramines can be responsible for corrosion of everything from door handles, light figures and benches to structural support beams in the ceiling, window frames and deck equipment. Chloramines can even damage the air handling system (not to mention bleaching out your swim suit).
“Where do they come from?” The simple answer is: people. Organic “particles” wash off our body, among other sources. The chlorine in the water attaches to these particles and creates a chloramine (hence “combined chlorine”). These little compounds have a pH of around 1 and can cause massive corrosion on metal surfaces when exposed for a period of time. One example of this occurred in Russia. Swimmers were killed when chloramines causes so much structural damage that the building collapsed!
“How do we deal with it?” You have two options when it comes to dealing with chloramines. You can either be reactive or proactive. The reactive method removes them after they have formed. The most common method here is air movement. Since chloramines are air born increasing your airflow can pull the chloramines out of the pool room once they form. This does result in corrosion on the air handling system, corrosion of metal near the air exhaust, and doesn’t deal with the effects the chloramines have on swimmers and spectators.
“What is the proactive option?” – There are a few simple options. The first is a non-chlorine shock. Using a traditional chlorine shock is likely going create more chloramines, among other D.B.P.s. It is easier just to avoid it. Our chemical of choice for the job is potassium-monopersulfate because it is effective, relatively cheap and does the job without creating more byproducts. Also, there is a short (24 hour) window where any remaining chemical will help break down those “particles” before chlorine can attach to them. Nifty, huh? This works for a large portion of the pools for a short amount of time.
Generally, as the water quality increase, so does the amount of swimmers. An increased in bathers leads to an increased organic load. An increased organic load then leads to increased combined chlorine. At this point shocking often begins to get expensive.
When the non-chlorine shock is no longer viable, whether due to demand or cost, there is another option: Ultraviolet Systems.
A UV system, sized correctly, can remove and continuously maintain very low (0.2-0.3) to no combined, eliminating the need for chemical shocks and helping to enhance water quality. The downside is obviously the cost of the UV. When chemicals are hundreds of dollars and equipment is thousands of dollars, many will veer towards the chemicals. However, keep a running tally on those chemical treatment costs, the lost revenue during the treatment downtime and the cost of maintenance crews to perform the work. When the math is done and pencil is laid down, it might be a better solution to bite the bullet and buy the equipment.
“Is there anything else I can do to prevent damage from combined chlorine?” The only real thing you can do to help prevent the formation of combined chlorine is to keep your pool well balanced. A well-balanced pool requires less chlorine to sanitize than an unbalanced pool. This will not prevent combined or remove it, but it is a good measure anyway.