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Corrosive Water Damage - Examples, Information and Causes

Corrosive Water Damage to Pool & Spa Equipment - Examples, Information and Causes. We've written this article with examples of photos of common damage to equipment caused by improperly-balanced water.

The number one cause of damage to spa equipment is chemical corrosion, often caused by low pH. Low pH & Total Alkalinity associated with Bromine, Trichlor & Dichlor chlorines can cause damage in a matter of days.

Products that show damage from Corrosive Water are almost never covered by any warranties from any manufacturers. They cover manufacturing faults. The below examples show damage outside of that scope. 

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. You may notice the water becomes fizzy in some cases.
  • Chlorine tablets: Trichlorisocyanuric acid (Trichlor) should never be used in a spa. It is simply far too strong, and extremely corrosive. Chlorine tablets can cause damage in as little as a few hours.
  • 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. 
  • Scaling: Scaling occurs when calcium levels are high, and often in conjunction with higher pH levels. This shows as a white deposit on some materials and the spa can sometimes feel like it has a gritty coating.
  • Salt-Chlorination & High Salt: Most spa equipment is not built for salt-chlorination or high-salt levels in the water. Salt-chlorinators bring a host of corrosive properties such as: salt itself, high-chlorine levels, and high pH.
  • high-pH / Caustic water: Caustic (alkaline) water is less common these days, but can still occur when the pH rises above 8.0. Most plastics are fairly resistant to high pH, but metals and other materials may be damaged. You can often feel when water is too alkaline, as it feels slimy. 
  • low-pH / Acidic water: Low pH makes Bromine & Chlorine more effective, but also damages everything else. Acidic water can sparkle and look fantastic, all while damaging equipment. Humans may not even notice how acidic it is, as our skin is mildly acidic on it's own, and can resist (temporarily) many low-pH environments.

Images & DescriptionsBelow:


Undamaged 10 Year Old Pump

10 Year old pump wet-end with good quality water. Notice the thermoplastic glass-reinforced Nylon still looks perfect. Almost all brands now use the same materials for their pump wet-ends.

Damaged 1 Year Old Pump

Same pump as above, but in a 1 year old pump with typical bromine tablet damage, causing whitening or yellowing of the glass-filled nylon. This can also be scratched with a fingernail. This 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 carbon 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. 

Pitting in 316 Stainless Steel (marine-grade). 316 Stainless is a very robust corrosion-resistant metal used in all sorts of industries. Damage to 316 SS is generally caused by corrosive water, and commonly starts in crevices first, where it continues to spread.

Most commonly due to low pH or high-halogens like Chlorine & Bromine.

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 caused by high bromine /chlorine & 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 corrosive water.

Filter cartridge plastic softening from poorly-balanced water. 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 typically 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.

  • Damage to metals is due to low pH (Acidic water) and/or high levels of Bromine or Chlorine. 
  • 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" (not chlorine!).
  • 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 ABS, Glass-filled Nylon, Polyurethane, Vinyl, Acrylic, and PVC.

    • Nylon, a thermoplastic) is used by all major manufacturers for parts like pump wet-ends, manifolds and more. It's extremely tough, but is not resistant to everything! Damage shows up as lightening of the plastic, glass fibres (used in reinforcement) 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 Materials - 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
      • EPDM & Viton are the most common materials used in o-rings and gaskets. 

        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

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