Pool to remain salt water

Trent Ernst, Editor

It’s official. The pool will not be switching to a chlorinated system.

Nor will it be switching to the proposed UV system, either.

For the last few years, Staff and Council have been working to figure out how to prevent the salt water in the pool from causing corrosion in the pool area. There has been a number of reports presented to Council concerning issues involving the existing disinfection system at the Aquatic Centre, and how it contributes to the deterioration of the building envelope and the damage caused previously and currently occurring to the walls, lighting, electrical, mechanical pool operating equipment and the overall rusting of the metals contained within the interior of the Aquatics area.

But a recent study of the pool has revealed that its not the salt that is causing the corrosion, but the fact that hydrochloric acid is used in the pool.

Some simple science. If a pool’s pH level is below 7, the water is too acidic and is hard on the body. If the pH is above 8, it is too base, and can also be hard on the system. The target range for a pool is between 7.4 and 7.6. This provides the optimum chlorine levels to prevent bacteria, algae and fungus growth, without developing scale, the white crusty substance often seen on pool tiles, or becoming too corrosive.

Small amounts of hydrochloric acid is often added to adjust pool water back towards this optimum range when it has become too basic.

However, hydrochloric acid is not the only chemical that can be added to the pool water. Sodium bisulfate can also be used.

Making the switch to sodium bisulfate, says a report by Boyd Clark, Community Services and District Facilities Manager, should go a long way towards resolving the problem of corrosion.

The pool disinfection system for the Aquatic Centre was initially designed with an ozone disinfection system supplemented by chlorine gas, but the chlorine system was replaced by a salt pool chlorine generator system in part due to the difficulties in operating and maintaining the ozone/chlorine gas system.

The use of salt chlorine raises the pools pH level, thus the existing chemical treatment system utilizes muriatic acid to lower the pH in the pool water, says Clark.

A report prepared by Rocky Point Engineering in 2015 discussed the issues at the pool, revealing excessive corrosion of metallic pool components and other pool related piping systems, as well as, elements within the pool hall such as hand-rails, lighting fixtures, door hardware, pump components and HVAC systems.

“It was believed that there was a correlation between the pool sanitization system and the corrosion,” says Clark. “Therefore there has been significant discussion over the suitability of this type of disinfection system. The Rocky Point Engineering Report goes as far to say that these are typical problems experienced with salt-chlorine systems. The Rocky Point Engineering Report suggests that the District should consider the installation of the Ultra Violet Pool Sanitization system as a means to rectify the corrosion problem.”

However when Clark started with the District a few months ago, he proposed bringing in a pool expert to come and take a look at the facility, as the UV system would be a major expense to the District.

So John Duiker, a pool master recognized in both Canada and the UK, of Automated Aquatics from Edmonton, Alberta was brought in to complete a pool evaluation and to provide a recommendation as to a long-term strategy for the District for the lifecycle upkeep of the mechanical operations of the pool.

His report, says Clark, focuses specifically on the pool mechanical equipment and is not reflective of the building structure and other operating systems independent of the pool operating systems (heat and air exchangers, lighting, electrical, security, structural, etc.). Clark says a separate engineering evaluation will need to be completed to address the current status of the building envelope and the various non-pool related operating systems.

In his analysis, Duiker says adding a UV System would not resolve the corrosion issue.

“The UV System is an add-on,” explains Clark. “The pool would still need some form of disinfectant to eliminate bacteria. Further, the UV System would in essence actually increase the chloramine count and probably add to the corrosion problem.”

In addition, says Clark, UV Systems are highly technical to operate compared to the salt water system and staff would need extensive training to that operate it. “As a result, an operator would more than likely experience increased operating costs initially through training, then on-going through continued technical support for operating,” says Clark. “Complicating this relationship is Tumbler Ridge’s remote location compared to where traditional UV operated pools are located. Support would have to originate from Vancouver, the lower mainland or Okanagan and therefore any trouble shooting would involve extensive travel costs annually.”

“In order to deal with the existing corrosion problem; the consultant recommends a simple solution. The elimination of the continuation of corrosion could occur by replacing the hydrochloric acid which is highly corrosive and with an extreme safety risk for staff handling with sodium bisulphate which is not corrosive and by far safer to handle,” says Clark. “This can be performed through a simple substitution in operating practices and can be still hand fed into the system.”

Indeed, says Clark, they are already moving towards this new chemical. It will probably result in a marginal operating cost increase, though the cost could be reduced through the implementation of an automated pumping system.

This means the money budgeted towards pool improvements—previously earmarked towards adding a UV system—can now be used to address other issues.

For years, Council has been told that the trouble with the pool was the salt water. Why the change? Clark says it is true that many communities have switched away from salt water pools because of the belief they were damaging their infrastructure. However, says Clark, a new wave of engineering thinking around salt water pools is taking place. “As per the new analysis the salt water system has been identified to have no correlation to the corrosion that has been occurring. Therefore the previous budget of $150,000 for replacement of the system can be re-allocated.”

Recently, staff has seen some issue with cloudy water and high chloramines in the air. Chloramines are what cause pools to smell like, well, pools.

“If you were to get down near the water surface and shine a UV light across the surface, you’d see a fog two to three inches off the water,” says Clark. “That’s the highest concentration of chloromines. So when a swimmer tilts their head out of water, they get a dose of that.”

When chlorine combines with perspiration, oils and other foreign substances that enter pools on the bodies of swimmers who haven’t showered properly before entering the pool, it forms chloromines

To help prevent chloromine build up, they will be installing a Wapotec filtration enhancement. “In laymen terms it is supercharging our filtration system,” says Clark. “It’s like putting it on steroids. Appropriately enough, considering where we live, it is adding coal to the sand filter, which improves filtration and reduced chloromides. This creates a purer system and reduces the amount of chloromides.”

Also being added is a DCM Controller. This is an automated system that will allow the pool to be monitored remotely. “We have this technology on the arena side of things,” says Clark. “We don’t have that on pool side. Most of what we do is manual. By going to an electronic system, it allows us to regulate when system is running.”

It also allows the pool to be monitored by pool professionals, he says. “For the arena, Symco systems can check the efficiency of system and troubleshoot issues from Edmonton. This will allow us to do the same thing, but with the pool. It allows us to have someone provide us that expertise from wherever they are so we can adjust water chemistry.”

One of the least expensive, but most important change, says Clark, is moving to electronic testing kits for water chemistry. “Up to this point we’ve used manual testing, which is a technology dating back to the eighties. The margin of error for these things is almost 20 percent. With the electronic testing kit, there is a margin of error of two percent. We’ll know where our water is at, be able to pass that information on to the pool company so they can troubleshoot and tell us what to do.”

Finally, says Clark, adding Inline Turbidity Monitoring will significantly improve pool chemistry, the bath experience, and reduce the impact of life deterioration of equipment.

These improvements, he says, are stage one and two of the four part pool upgrade proposed by Duiker.

Stage three will be to replace the mechanicals for all three pools, which will cost about $250,000.

Finally, says Clark, over the next five years, replacement parts for the current salt water chlorination system will start to become harder to find. “The existing system is dated but operational. It is important that the operator replace the cells annually; however it is expected that replacement cells will be difficult to obtain beyond five years as new systems are being introduced from Europe.”

All tolled, the cost of pool upgrades over the next five to ten years will run about $680,000. While the new information comes too late to be done during the current pool shut down, Clark says most of the work can be done during periods of time when the pool is operational, but not open.