Pool Info: Metal Control
Are there Metals in your Pool?
Does your pool have metals in the water? Indeed, all water contains trace amounts of metals like iron, aluminum, manganese, zinc and silver, copper, even gold.
Metals in pool water are always there, but usually dissolved in solution. It is a problem only when they come out of solution, to discolor the water or deposit as pool stains. This can happen by oxidation from shocking the pool, especially when the pool water balance is incorrect.
Metals in the pool are not toxic and even very high levels in the pool are not a concern for swimmers. They also do little to interfere with water balance, although they are affected by it. The main problem is an aesthetic issue; metals and minerals can cloud the water or stain underwater surfaces.
How do Metals get in a Pool?
The most common metals in pool water are iron and copper. They occur naturally in well water, and are also found in municipal water, in lower amounts. Iron and copper can enter the pool from deterioration of metal pipes anywhere in the water supply, or in older pool plumbing. Many pool heaters have copper heat exchangers and cast iron headers, which erode with acidic and aggressive pool water chemistry.
Copper or Silver pool algaecide is another way that metals can enter a swimming pool. These are powerful algaestats, and over-use can lead to pool staining or discoloration. Use of Power Ionizers or floating solar ionizers, which make use of copper and silver ions, elevates the level of these metals to fight bacteria and algae, and can lead to pool staining or water discoloration.
Metals can accidentally find their way into the pool; hair clips or non-pool toys are common sources. These typically produce only isolated rust stains where the metal object was laying on the surface, and do not raise metal levels in the water. Many lawn and garden fertilizers can contain high levels of iron, copper, manganese and other heavy metals. Heavy rains and flooding with mud or mulch entering the pool will also elevate metal levels.
Testing Pool Water for Metals
Metal Test Kits: Only the most expensive pool test kits like the ColorQ Pro 11 have a test for metals, yet it only tests for Copper and Iron. Taylor has a good Copper Test Kit, or AquaChek has a Copper Test Strip. To measure other heavy metals and for a complete chemical makeup of your pool water (or fill water), you could send a water sample to NTL or other laboratory.
Chemical Reaction Tests: For stains on a pool, you can test with chemicals to see if the stain is organic or metallic. Sprinkle pool shock or place a chlorine tablet over a stain, and if it lightens or disappears, the stain is organic, from algae, leaves, or dirt and oil. If chlorine applied directly does not remove the stain, it is usually not organic, but metallic.
An opposite test is to use ascorbic acid on the stain. Crush up several vitamin C tablets, or use Stain Free, a granular ascorbic acid for pools, and sprinkle the powder over the stained area. A similar acid test uses pH decreaser, added to an old orphan sock, to create what is called a stain bag. Most metal stains will lighten or disappear with acid directly applied.
The Color Test: An offhand method of determining the presence of metals in your pool relies on the colors of stain and scale imparted to the pool water, or deposited as stains. Certain metals exhibit specific colors when they come out of solution and are free-floating, or deposited as a stain.
High levels of Copper will present itself in a bright, clear green hue when suspended in the water, or as teal colored stains when deposited. High copper levels can also turn blonde hair a green tint, or discolor fabric pool products like DE grids, filter cartridges or pool cleaner debris bags.
High Iron levels can turn your pool into brown tea when suspended, or deposit on surfaces as a rusty red/brown color. High levels of Manganese and Magnesium can actually turn your pool a purple color, and Silver commonly forms black streaks or discolorations when it drops out of solution.
Treating Fill Water to Remove Metals
If you have determined that you have high levels of metals in your fill water or home water supply, you can use a pre-filter on your fill hose, to remove solids, impurities and metals from the water, before it enters the pool. If your home water supply comes from a well, another option may be to add fill water to the pool from the kitchen or laundry room. Outside spigots are not usually connected to the home water treatment system, which can remove most metals from the well water.
Filtering Metals out of Pool Water
Minerals and metals are extremely small particles and pass right through your pool filter. Capturing microscopic metal molecules requires filters of much higher efficacy than those used on swimming pools. In some hard water areas of the country, pool water recycling companies are in operation, offering truck mounted reverse osmosis pool water filtration, which removes metals, minerals and more. Pool metals are also unresponsive to clarifier and flocculent chemicals.
Pool Metal Removal Chemicals
One method of absorbing metals is the patented CuLator Metal Eliminator and Stain Preventer. The CuLator PowerPak fits into the pump basket and absorbs up to 4 ppm of metals over a 30-day time.
Sequestering Agents are chemicals used to bind-up minerals and metals in solution, making it difficult for them to precipitate out of solution to cloud the water or stain the pool. They do not actually remove metals from the water, but keep them ‘sequestered’ or locked in solution with tight chemical bonds.
Sequestering Agents like our Stain Away, Natural Chemistry’s Metal Free and the Blue Stuff by Jack’s Magic, are used to prevent pool staining from metals and minerals. Stain & Scale chemicals keep metals safely dissolved during pH fluctuations, high chlorine levels or other water conditions that can knock metals and minerals out of solution.
Pool Metal Stain Removal
The Stain & Scale chemicals above are used to control or prevent metal staining and mineral scale, and although they usually lighten existing pool stains, they often struggle with stain removal. Acids are used to remove underwater pool stains without draining the water.
Sodium Bisulfate Also known as pH Decreaser, pH Minus or pH Down, is less effective because it dissolves so rapidly, but is less costly to purchase.
Pool metal stain removers dissolve metals back into solution; they do not destroy or remove the metals. Follow chemical recommendations carefully during application, and be aware that temporary metal staining may occur immediately after treatment. Follow-up stain removal with a good sequestering agent, and then bring chlorine levels up slowly.
Acid Washing: For plaster pools, an alternative solution is to drain the pool and perform an acid wash. This involves a hazardous process using muriatic acid to purposefully strip a thin layer of plaster from the pool walls and floors. Works well to remove stains, even stubborn copper stains, but requires careful planning and execution. Acid washing is not an option for vinyl liner pools. Refill the pool with a pre-filter to remove metals, and add a sequestrant immediately after balancing the water.
No Drain Acid Wash: An alternate form of acid washing (for plaster or pebble pools), that involves adding large amounts of pH decreaser to lower the alkalinity level to 0.0, and the pH to around 3.0. Remove lights, ladders, pool cleaners and other fragile items before treatment. Leave the pool pump off for 24-48 hours, and then add Soda Ash to raise the pH and Alkalinity to normal ranges.
Spot Removal: Attached to your pool pole, acid delivery tools like the Jandy Stain Master or the Purity Out Spot Stain Remover deliver liquid muriatic acid to a small area of a plaster pool. Very effective on localized stains, but ill-suited for stain removal on a large scale.
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