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How To Remove Swimming Pool Stains

Courtesy Sparkling Clear Pool Care

"There are two types of pools: those that are stained and those that are going to stain."

This is a well-known saying in the pool profession. Stains and discoloration on a pool's surface come in many different forms and come from a variety of different sources, most of which you have little to no control over. Maintaining properly balanced water is the best way to prevent or postpone staining because unbalanced water can act as catalyst for stains and discoloration. When those annoying spots do inevitably pop on your pool's surface, it is important to be able to identify the discoloration, start the removal process, and prevent any future staining.

Organic stains are very common in pools

When a stain is a brownish green in color, it typically means it is related to something organic. The most common cause of organic staining is something like a leaf, algae, or a dead worm that lies on the surface of the pool. The organic matter and tannins cause the surface of the pool to stain and discolor. Sometimes these stains can be removed by simply shocking the pool with chlorine and scrubbing the stain with a stiff brush.

If this method does not lighten or remove the stain, a natural ascorbic acid based product or diphosphonic acid based pool stain remover can be used. Ascorbic acid is found in citrus juice. The vitamin C is what helps remove the stain. Using these products will help remove more stubborn stains but may require some tough scrubbing or even draining the pool so you have better access to the discolored area.

Building a homemade scrubber that uses muriatic acid is a great way to remove stubborn "old" stains that are scattered around the surface of the pool. However, using muriatic acid in a device like this can cause the plaster in the spot you are working on to bleach and become lighter than the rest of the surface. If the pool surface is older and the organic materials in the water have caused the majority of the surface to discolor, an acid wash can be a good option. This involves draining your pool and using acid to remove a small layer of the surface, which bleaches the plaster, and results in fresh, clean looking surface. This method is expensive and can only be done a few times throughout the lifetime of the surface.

To prevent future organic stains, the most effective thing you can do is keep the pool free of debris and critters by vacuuming, brushing, and netting the pool regularly. If a pool stain is not of the organic variety, it is most likely caused by metals in the water.

The following are some common sources of metals and minerals that may eventually end up in your pool water:

  • Metallic equipment parts such as heat exchangers, brass valves, and copper or galvanized plumbing.
  • Water added to your pool to make up for loss due to evaporation, leaking, backwashing filters, or splashing.City water often has added metals and minerals for sanitation purposes.
  • Well water added to a pool is full of metals such as copper, iron, manganese, and magnesium.
  • Pool chemicals such as algaecides contain copper and silver, and pool salt can even contain small amounts of iron.
  • Lawn chemicals such as fertilizers and pesticides all contain metals and will most likely end up in your pool one way or another.

The two most common types of metal staining are iron and copper stains

Iron comes from well water, pool equipment, and almost any pool chemical that is used to treat the water. Iron stains will be brown in color. They are purely esthetic and will not compromise the surface if left untreated. In some cases iron and calcium can form a compound that is referred to as iron scale. In this situation, the stain is covered by scaling so treatment must be applied to the calcium scaling as well the iron to remove the discoloration. This type of stain is textured and will get worse over time if left untreated.

Copper staining can come from city water, algaecides, and heat exchangers with copper piping that wear down over time and eventually feed copper into the pool. The color of the stain may be blue, green, black, brown, or even purple. A blue or green color typically indicates that the copper is still in sulfate form and will need to be oxidized before it can be treated. Copper stains are probably the toughest to remove but are completely esthetic and will not harm the surface of the pool if left untreated.

As metals accumulate in a pool the risk of metals coming out of solution becomes greater

Once the metals come out of solution they can "plate out" on the surface of the pool leaving stains and discoloration. Metals can come out of solution when the pool is shocked because the chlorine oxidizes the metals. Oxidized iron becomes rust, hence the reddish brown color of an iron stain. Metals can also come out of solution when the pH, alkalinity, or calcium hardness levels in the water are too low. In this situation the water becomes aggressive and the metals are more susceptible to oxidation. Metals can only be tested when they are in solution. Once they oxidize and "plate out" on a pool's surface the metal test will show nothing. When a metal stain has occurred that particular metal may not show up when the water is tested.

Keeping your pool in balance can nip staining in the bud!

To help prevent metals from staining your pool surface it is important to properly balance the water, keeping the pH between 7.4 and 7.6, the alkalinity between 80 and 120 ppm, and the calcium hardness around 300 ppm. Using a product like Jack's Magic Pink Stuff or Blue Stuff when initially filling the pool or adding make up water to the pool can help remove metals present and prevent staining. When attempting to remove existing stains, it is important to first properly balance the water to prevent the occurrence of more staining.

Chemical solutions to the staining problem

For light copper and iron stains, BioGaurd Pool Magnet works well on "fresh" stains. For heavier staining, Jack's Magic Blue Stuff is an effective additive which can also be used in higher chlorine levels, so treating metal in water that also has algae issues can be done at the same time. Products like these are sequestering agents that suspend the metals in solution to prevent them from "plating out" on the surface. As with stains caused by something organic, using an ascorbic or diphosphonic acid based product can help remove metal stains. When treating metal stains and discoloration with products such as these, the results may not be immediate and you may not see the stain lighten or be removed for several days or several weeks. The device discussed earlier that uses scrub pads and muriatic acid can also be effective on metal stains and shows instant results.

Pool stains can be a major annoyance for a pool owner!

Whether they are caused by organic materials or metals, stains can be hard to identify and remove. All of the removal methods discussed above can be effective. Which one you choose will depend on the source of the stain, the severity of the stain, and the cost of products involved. The muriatic acid stain scrubbing device is something that can easily be made at home in less than an hour, it is inexpensive, and is a great way to spot clean stains on the surface of your pool. Instructions on building and using this device can be found below.

Do it yourself pool stain removal deviceBuilding And Using Your Own Stain Removal Device

Building your own, homemade stain removal device is easy and takes less than an hour to construct. This is a great tool to remove stains and discoloration on your white plaster pool. Do not use this method of stain removal for dyed plaster or vinyl pools as it could bleach dyed materials or remove liner patterns. To construct the device, you will need the following items that can be found at a local home improvement store:

  • 2 square scrubbing pads
  • 1 sure seat wax ring cap (normally used for toilet installation)
  • 1 metal hose clamp that will fit a 1 ½ inch PVC pipe
  • 1 12 foot section of 1 ½ inch PVC piping
  • 1 6 inch section of 3 inch PVC piping
  • 1 3 inch x 1 ½ inch PVC reducer 1 3 inch x 3 inch x 1 ½ inch PVC reducing wye
  • 1 3 inch cap 1 1 ½ inch coupling
  • 1 can PVC glue 1 can PVC primer 4 small screws

Next, follow these easy steps to assemble the device:

  1. Cut the 6 in. section of 3 in. PVC in half
  2. With your primer and glue, use one of the 3 in. sections of 3 in. PVC to connect the 3 in. cap to the top of the 3in. x 3in. x 1 ½ in. reducing wye (make sure reducing section of the wye is angled with open end pointing up)
  3. With the other section of 3 in. PVC, use primer and glue to connect the reducing wye to the 3 in. x 1 ½ in. reducer
  4. Use screws to attach two scrubbing pads to the bottom of the sure seat wax ring cap
  5. Place the metal hose clamp around the hole in the rubber seal on the wax ring cap, insert the end of the device with the 1 ½ in. reducer into the rubber seal on the wax ring cap, and tighten the hose clamp to secure
  6. Insert the 12 ft. section of 1 ½ in. PVC into the angled section of the reducing wye (depending on the depth of your pool, you may need to extend the 12 ft. section of PVC by adding more 1 ½ in. piping, use the 1 ½ in. coupling for this)
  7. Want more help making this fun and useful device?  Here is a video of the project, courtesy Sparkling Clear Pool Care.

Your stain device is ready to use!

Now you can grab your device, a bottle of muriatic acid, and you are ready for stain removal. Here are some steps and tips for the removal process:

  1. Place the device in the pool with the scrub pads covering the stained/discolored area
  2. Carefully poor a small amount of acid down the 1 ½ in. pipe (the fumes from this product can be harmful so use caution)
  3. The acid is more dense than water so it will settle down through the wax ring cap and disperse throughout the scrubbing pads
  4. Using a bit of pressure, move the device back and forth to scrub the desired area
  5. You should see the stain lighten fairly quickly
  6. Be cautious of the amount of acid being used and the force with which you are scrubbing, because this device can bleach the area too much, and if the rest of the surface is old and lightly stained, you will notice a difference where the plaster was bleached by the acid
  7. Use a little more acid if necessary, and keep scrubbing the stain until it is completely removed.

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