Strategies for chloramine removal: Best practices for maintaining proper air and water quality at indoor pools

Chemical treatments

Dilution

‘Dilution is the solution to pollution.’ In most cases, this method can work to reduce chloramines, total dissolved solids (TDS), and other contaminants in pool/spa water. If the source fill water contains chloramines they should be removed before they enter the recreational environment to prevent any problems. Therefore, it is important to know what is in the source water.

As of July 1, 2018, the Ontario Health Protection and Promotion Act Regulation 565 Section 7, subsection 13 (R.R.O.1990, Reg. 565, s. 7 [13]) states:

(13) Every operator shall add make-up water to the pool during each operating day in a minimum amount of 15 L (3.96 gal) per bather as determined by a water meter installed for the purpose.

For those pools not under the authority of Ontario Regulation 565, another method to achieve dilution of these contaminants is to purposefully drain 51 to 102 mm (2 to 4 in.) of water out of the pool each week after closing to the public and replacing it with fresh fill water. This 51 to 102 mm (2 to 4 in.) of water is in addition to normal water loss from bather splash-out/run-off, evaporation, and backwashing tasks.

Once the water has been added, the pool water needs to be tested and the chemical balance should be adjusted accordingly. Depending on how many bathers/swimmers have been in the water during that last week determines whether to use the lower or higher level of this dilution range. By performing this task at closing it allows the fresh fill water to be heated overnight so water in the pool/spa reaches the appropriate temperature when opened the next morning.

Due to the higher bather-to-water ratios in spas/hot tubs, water replacement is a more effective and economical strategy then continually adding more chemicals to try and maintain healthy water. Completely draining and filling the water in spas/hot tubs is the standard strategy rather than partial replacement as these vessels typically contain a much smaller volume of water than a pool.

The suggested method of determining when to drain a spa/hot tub may be different based on where the facility is located and may not be specified in the local regulations. The most common formula to determine when to change the water in a spa/hot tub is:

Water replacement interval (WRI) (days) = (¹/₃) x (water volume in U.S. gallons) ÷ (number of bathers per day).

In Ontario, the regulation guiding draining for spas/hot tubs under 4000 L (1056 gal) is:

WRI (days) = Total volume in litres ÷ (10 x Total estimated number of bathers uses per operating day).

Essentially, what this formula says is the number of days between water replacements, or draining the spa/hot tub, is when the number of bathers who have used the spa/hot tub equals one-third the gallons of water in the vessel.

If the spa/hot tub holds 1514 L (600 gal) of water, then one third of that is 757 L (200 gal). When approximately 200 bathers have used the spa/hot tub, it should be drained, flushed, and refilled with fresh water. Then, the system should be restarted and the water chemistry adjusted back to proper levels.

Keep in mind, in spas/hot tubs chemicals are typically added in measurements of teaspoons and tablespoons, making it a fairly inexpensive way of handling bather waste, TDS, and chlorine demand issues.

Aeriation

In France, one solution to this problem is to aerate the water outside to confines of the pool enclosure forcing the volatile combined chlorine into the atmosphere. Air is forced into a chamber, such as an exterior surge tank, and the combined chlorine goes from an aqueous form to a gaseous form, allowing the bad air to be discharged where bathers are not present.

Breakpoint chlorination

When combined chlorine concentrations exceed 0.2 ppm in the water it may start to produce eye and nasal irritation as it is gassing off into the pool atmosphere. One of the simplest and least expensive ways to deal with this is called breakpoint chlorination.

If the concentration of combined inorganic chlorine in the water is known, it can be burned off chemically by adding 10 times the concentration in new, free chlorine to the pool water. For example, if the combined chlorine concentration is 0.3 ppm, it would take 3 ppm of new free chlorine to burn off the combined inorganic chlorine present in the water. How much product this would entail depends on the form and concentration of the chlorine product being used.

This process will remove the odour of the ammoniated combined chlorine which is what most people are worried about. However, it will not be sufficient to remove the organic chloramines that may buildup over time. A dilution program or one of the following strategies must be employed to remove these.

How often is breakpoint chlorination needed? It depends mostly on bather load, gallons of water the bather load is impacting, and how quickly the chloramines build up. In a busy facility this might need to be performed daily as part of the closing procedure. On the other hand, in a small, rarely used venue, this might have to be done only once a week or even every two weeks.

When volatile chloramines go into the venue environment the air handling system (HVAC) is tasked with removing these gasses and discharging them outside.

In some cases, there are insufficient fresh air exchanges in the venue and these gasses remain in the environment. When inhaled by bathers/swimmers and staff, they can potentially create breathing problems. In some pools this insufficient fresh air is such a great problem that when the venue is being breakpoint chlorinated the fire doors need to be opened and exhaust fans set up to force the malodorous air out of the building.

If these volatile chloramines are not removed from the air and are allowed to sit above the pool surface, these gasses go back into water thereby increasing the concentration.

As for pool and spa/hot tub regulations in Canada, some provincial codes put limits on the combined chlorine concentration in the pool water, but due to the complexity of testing chloramines in the air, the limits are not regulated. The regulations in Ontario (R.R.O.1990, Reg. 565, s. 11 [1]) state:

(1) Every owner and every operator of a public pool or public spa shall ensure that the pool or spa, the deck and, where provided, the dressing and locker rooms, water closets, showers and connecting corridors appurtenant to the pool or spa are,

        (a) Kept clean, free from slipperiness and disinfected;

        (b) Free of hazardous obstructions; and

        (c) Ventilated so as to remove odours.