Tri-Chlor Sales Increase Means More Damaged Spas

Unwitting hot tub owners are unaware of that by using Tri-Chlor tablets on their hot tubs, they could invalidate warranty claims.


Leading spa suppliers and water treatment specialists are expressing concern over increased sales of Tri-Chlor tablets, mostly via the Internet, to unwitting hot tub owners who are unaware of the potentially detrimental effect on their hot tubs, especially to heating components.

Tri-Chlor tablets are designed for use in erosion feed chlorinators as their concentrated and acidic nature makes them hazardous to handle. If used in a hot tub in any other way, their low pH and corrosive nature can damage surfaces and equipment, especially where spa water becomes acidic damaging seals and parts.

Where Tri-Chlor tablets are used and damage caused, many spa warranty claims are deemed invalid as the failure is due to incorrect maintenance rather than a manufacturers’ fault. Soft water areas in parts of North Wales, South Wales and the South West are bearing the brunt of the problem. “In the past few years there has been a surge in demand for Tri- Chlor tabs (TCCA) as many home spa owners find it easier to dose the sanitiser in a floating dispenser and re-fill when required,” confirms James Lee of Water Treatment Products.


“The main issue with this method of dosing is that the tablets are particularly corrosive as the chemical composition is very acidic. “Therefore, as this product breaks down, it will also create an acidic environment especially if the heat cover is in situ,” he adds. “The environment between the surface of the water and the underside of the heat cover is enclosed and will be subjected to this acidic environment and over time, damage can be sustained to fitting and fabric.

“Mindful of the generic water conditions, particularly in the South West and North West, with very soft water, adding Tri-chlor to the mix simply creates an acidic chemistry that is only going to exacerbate the situation.” Most leading hot tub companies make it clear that the use of Tri Chlor tablets invalidates a manufacturer’s warranty. “We do not recommend Tri-Chlor tablets in our hot tubs as they have to be fitted in a floating dispenser,” confirms Ray Wells of Hotspring World. “As they dissolve into the water they produce a fairly strong acid solution which then dissipates into the water providing the necessary, very weak solution required for sanitisation of the spa. “As the dispensers always seem to end up in one position in the spa, against the weir gate through which the water is drawn, this means that one particular part of the hot tub shell is constantly exposed to a strong concentration of acidic solution,” explains Ray. “This can result in a discolouration and a weakening of the shell. This is why we do not recommend their use.”

Where Tri-Chlor tablets are used, many spa warranty claims are deemed invalid as the failure is due to incorrect maintenance rather than a manufacturers’ fault.


Vicky Wrigglesworth of Artesian Spas says: “I am told by the factory that they are the worst for wear and tear on the wearable items of the hot tub such as pillows. “The problem usually comes if people add too much into their water and tablets can be hard to regulate unless a customer purchases a good dispenser that allows proper graduation,” she adds.

Lloyd Burden of Hydropool agrees: “Over time, the impact using these tablets in floating dispensers can see a degrading of plastics such as heat covers, head rests and potentially metallic fittings such as jet housings and returns. “A good way to minimise the impact of this chemistry is for the hot tub to have a ‘built-in’ erosion feeder, whereby the tablets are, in effect, in their own vessel and have minimum contact with the fabric of the hot tub but have maximum contact with the water,” explains Lloyd. “Hydropool employ this in all their self-cleaning hot tubs. Clearly some of our competition have issues,” he adds.

Tri-Chlor is a very effective disinfectant in both swimming pools and spas however it does have an effect of lowering the pH due it creating an acidic environment. The reason of low pH of recreational waters, such as pools and spas, is that when TCCA is used hydroxylation occurs which gives Free Chlorine (Hypochlorous Acid/HOCl) and Cyanuric Acid (CA). The HOCl in water can hydrolyze to hydronium ion and hypochlorite which will decompose to chloride ion. Cyanuric acid also decomposes to hydronium ion and cyanurate. Typically, the higher the concentration of hydronium in water, then the lower pH level of pool water can be observed.


Hot tubs located in soft water areas, such as large areas of South Wales, the South West and parts of North Wales, are particularly susceptible to Tri-Chlor tablet damage.


“I am not quite sure how bad the actual situation is across the whole of the UK however the product does need to be managed well by end users when looking after their pools and spas,” says Paul Grunhut of Total Water Products. “In essence, the lower the pH in the spa will make the water more corrosive and corrosive water can attack the structure of the spa’s internal parts – especially heat exchangers,” he continues. “It necessarily follows that in areas of soft water on incoming mains, such as large areas of South Wales, the South West and parts of North Wales, then the slightly corrosive nature of the incoming source water would further compound the issue,” he adds. Paul says another effect of using TCCA will be that a higher concentration of CA levels in the water which can be a disadvantage in terms of the chlorine efficacy/protection. Beyond 30 ppm (mg/L) cyanuric acid becomes a deterrent rather that a help for allowing chlorine to do its job of killing bacteria.

It lessens chlorine’s effectiveness because the chlorine becomes progressively over-stabilized. This leads to a situation known as ‘chlorine lock’. Chorine is ‘locked up’ by the high levels of cyanuric acid and is unable to work normally. Says Paul: “Some spa operators misunderstand this and then add more TCCA in order to obtain higher chlorine efficiencies that results in too much cyanuric acid built up in the water, again causing in low pH of water. “Spa owners should be following the BISHTA standards of dumping the water every 12 weeks, then over stabilisation can be controlled more effectively however it goes back to the old principle that owners should be keeping good balanced water,” adds Paul. “This will be achieved, especially when using TCCA, by ensuring they are testing the necessary water parameters by using an industry recognised test kit and making the necessary chemical adjustments in order to keep their water in balance.”