The number one cause of damage to spa equipment is Bromine. Bromine Tablets have been a convenient staple for sanitising spas and hot tubs for many years. There are still a handful of pool shops recommending them, but the Spa Industry has moved away from Bromine Tablets for many reasons.

Low pH & Total Alkalinity associated with Bromine usage, and the corrosive nature of Bromine itself, are the biggest cause of damage to spa equipment. Unchecked Trichlor & Dichlor chlorines can also cause similar damage.

Never let a Pool Shop sell you Bromine Tablets or Chlorine and tell you “That’s all you have to add.Bromine is usually sold by Pool Shops due to ignorance, and its ease of use. Any spa expert or equipment manufacturer will tell you to avoid Bromine Tablets. Brominated water often looks sparkly and clear...this is often because it's so acidic & corrosive that nothing can live in it!

  • Bromine tablets are no longer recommended by any major spa manufacturer.
  • Most equipment manufacturers will void warranties where bromine tablets are used.
  • Bromine has been banned in some countries, and by products such as Brominated DBPs and Bromates may have serious health implications.
  • We strongly recommend you to switch to Liquid Lithium, Iluka Mineral System, SpaCare Sanitiser, AquaSpa (chlorine-free), or similar sanitiser systems. As with any chemicals, it is still important to keep your water balanced, not just "sparkly."

Common causes of Corrosive Water:

  • Bromine tablets / Dichlor powder: This is by far the biggest source of corrosive water. Bromine itself is very acidic. It can make the water look absolutely sparkling. If not kept in check by regularly emptying and refilling the spa *AND* most importantly, by keeping the pH and Total Alkalinity up it can become corrosive very quickly. Many manufacturers will instantly void warranty where signs of bromine are used.
  • Chlorine tablets: Trichlorisocyanuric acid ("Trichlor") should NEVER be used in a spa. It is simply far too strong, and extremely corrosive. No warranty will be valid by any manufacturer where this is used. 
  • Generally low-pH: usually overdosing with Acids. Low pH makes Bromine & Chlorine more effective, but also damages everything else.
  • "Cheap" Calcium-based chlorine. Some of the cheapest chlorine on the market comes as a powder, and is called "Calcium Hypochlorite." This can be as much as 70% calcium, which never comes back out of the water. The only way to remove it is by emptying water. 

Images & Descriptions of Damage Due to Corrosive Water

 
Undamaged 10 Year Old Pump
10 Year old pump wet-end with good quality water.
Damaged 1 Year Old Pump
Same brand as above, but in a 1 year old pump with typical bromine damage, causing whitening or yellowing of the glass-filled nylon. This can also be scratched with a fingernail. Damages mechanical seals and can cause impeller plastic to become thin.
Mechanical Seal Damage - Corrosive Water
Typical damage of the carbon-face of a mechanical seal. Notice the softenning and pitting of the surfaces. Also damages rubber components of the seal set.
Pump Shaft Corrosion
Corroded and swollen motor shaft. Leaking mechanical seal causes water to get behind impeller. This eventually damages the motor shaft, front bearing, end-plate and more. 
Typical damage to a heater element. Note the extreme damage to the incoloy metal. This can cause leaks and electrical shorting. 
Very typical damage to a Davey heater element. Davey, Spa-Quip, SpaNet use similar heater element materials. Note the damage to the PTFE/Teflon coating. This is only caused by Bromine & acidic water. Damage can occur within days.
Heater element with PTFE/Teflon damage. Once the Teflon coating is damaged, materials like brass or quickly damaged as well.
Long term damage due to leaking mechanical seal. Caused by too many bromine tablets and unchecked pH.
Filter cartridge plastic softening. Notice the colour bleaching, how the surface becomes soft and gummy, and the feathering of sharp edges. 
Polyurethane filter damage. Bleaching & Cracking occurs after the plastic is softened due to corrosive water. 
Vinyl liner bleaching and complete breakdown due to low pH & Trichlor tablets.
Filter cover vinyl bleaching and bubbling. Caused by Bromine vapours.
Acrylic damage due to corrosive water.
Brass Fitting - New vs Old. Note the major pitting and general corrosion. Cause by low pH.
Cupro Nickel heat exchanger badly damaged within 12 months. Tubes start off nearly 1mm thick, but become paper thin. This was caused by Trichlor tablets, but is common with Bromine tablets as well.
A perfect example of what most people first notice with a Balboa heater leaking where the seals have failed due to corrosive water.

An interesting example where you can see multiple issues caused by acidic water with Bromine use. 

1. PTFE/Teflon coating completely removed from element.

2. Large Brass nut corroding, growing in a crystalline structure.

3. You can see the softening of the black glass-filled Nylon (Noryl) casing.

Mechanical seal damage, causing water to corrode motor shaft. Very typical damage that can make repairs very difficult, or even impossible.

Brass Plugs from a Gas heater. Completely destroyed by over Bromination and acidic water. Note the discolouration as well...this is due to the acidic water actually penetrating into the crystalline structure of the brass.

Stainless Steel & Brass Temperature sensor corroded.
Typical damage by Bromine to spa jets. Parts of the Jets become brittle, peel, and snap off.
Very typical pinhole in gas heat exchanger. Entire copper and copper nickel heat exchanger thins out when this occurs.

 

Common Corrosive Damage:

Metal corrosion - Spa equipment really only uses Stainless Steel, Bronze, Copper, Incolloy, Cupro-Nickel, Teflon-coatings and Titanium material for things like Impeller shafts, Mechanical Seals, Heater Elements, Heater Tubes, Heat Exchangers, etc.

  • The only real cause of damage to metals are due to low pH (Acidic water) and/or high levels of Bromine or Chlorine. Humans often don't even notice the water having a low pH, and many people don't notice the effects on their skin. If you notice the water is fizzy, or you have dry skin after using a spa or pool, there's likely something not right.
  • On gas heaters this can be the source of green or blueish water. This is from dissolved copper, and is the source of "green hair."
  • On electrical heaters this can show as signs of dissolved Teflon, crevice corrosion, pitting, leaking at terminals, etc. Often causes Errors and Tripping Power.

    Plastic Corrosion - many plastic parts are made of things like ABS, Glass-filled Nylon, Polyurethane, Vinyl, Acrylic, and PVC.

    • Nylon is used by all major manufacturers for parts like pump wet-ends, manifolds and more. It can quickly shows signs of damage. This shows up as lightening of the plastic, glass fibres being exposed, or general dissolving. (eg, can be scraped with a fingernail)
    • PTFE (Teflon®) is used as a coating on many manufacturer's heater elements. Signs of corrosive damage are blistering, cracking, peeling, discolouration, and more. PTFE is also quickly damaged if water flow is poor through a heater.
    • Jets show signs of plastic damage by lightening, sloughing, peeling, or brittleness. (commonly causes jets to pop out as the retainer tabs snap off)
    • Cartridge Filters made of Polyurethane (all major manufacturers such as Pleatco, Magnum, Darlly) will soften, lighten in colour, and become easily scraped by a fingernail. It can be seen first by a kind of "flowering or feathering" of sharp edges. Pieces may come off. 
    • Polyester in cartridge filters is fairly robust. Long term the polyester may start sticking together, reducing water glow.
    • PVC is fairly resistant to corrosion, but long-term can cause brittleness.
    • Vinyl is generally found only in Spa Covers although inflatable spas are made entirely of vinyl. Pool liners are also Vinyl. Vinyl damage starts off as bleaching, then creates softening, bubbling, flaking, and more. 
    • Acrylic is generally found in spas. Acrylic is fairly resistant but can sustain damage such as bleaching, bubbling, delaminating / peeling, or complete breakdown.
    • Glues can break down, discolour, delaminate.

      Other signs - O-rings, gaskets, seals & sensors.

      • O-rings, gaskets and seals can also show signs of corrosive water in the form of Dissolving, becoming "gummy", cracking, hardening, etc. When any of these things occur, they may leak.
      • Optical sensors often show signs of cloudiness or cracking.
      • Signs of Calcium can also appear on equipment

        Testing for Corrosive Water on Equipment

        • Corrosive water can be shown by testing the materials with specialized kits where it is suspected, although visual inspection is enough in most circumstances. For manufacturers and repairers, it's fairly obvious generally.

        More Information

        Davey Spa-Quip Non-Warranty Information Sheet - This PDF has some good examples and information about damage not covered by warranties, due to corrosive water.

        Other Spa Companies That Oppose Bromine Tablets