Blemish Imperfections

Common causes and treatments for pool stains

An assiduous pool pro does everything to keep the client’s pool looking pristine. After all, pools are as much an aesthetic feature as they are a functional one. Unavoidably, however, pool stains can occur. Understanding how and why, as well as what to do to prevent and remove them, are all part of the pool service gig.

“The most common issues we see with staining across the board are due to poor and unhealthy water chemistry conditions,” says Josh DeRoche, president of Pool-Aid in Nederland, Texas.

While most service professionals will tell you that they see minimal staining once they’re on the job, there are still factors that are out of the pool pro’s control, such as what items the client allows in the pool. John Poma, owner of A+ Pool Service in Lakeland, Florida, says he’s seen stains come from toys left in the water, such as squirt guns and toy cars. “What is left in the pool for any time, if it has metal, it will leave a stain,” he says. In these cases, Poma typically does a spot stain removal treatment or uses a vitamin C tablet on the site of the stain.

Iron levels in tap water can also cause stains even when the pool is regularly maintained. “Source water can vary from houses just a block from each other, even if they are in the same city water district,” DeRoche says. “Metals fallout can happen anywhere.”

High iron levels are especially common for pools where source water comes from a well, says Kevin Stempien, owner of X-Pert Pool Service in Throop, Pennsylvania.

“Please don’t use well water when you don’t have to,” DeRoche says. “The money you save typically works out in the long run — between stain treatments, filter cleanings and the cost of a less than pristine and perfect pool surface.” 

When Poma finds that the cause of a stain is iron in the source water, he prefers to do a whole pool treatment using ascorbic acid. He also recommends that a metal remover be used in the pool on a regular basis.

Stempien uses United Chemical’s Pool Stain Treat in these circumstances. While the Pool Stain Treat powder is available in spotting bags, Stempien prefers to make his own on site by placing some of the powder in a stocking, along with glass marbles for weight so it stays in place in the water. “I use marbles for weight because some stones contain iron,” he says.

Copper staining can come from pool heaters if the water chemistry is not balanced, says Jesse Derr, president of Accurate Pool and Landscape in St. Louis. “A low or high pH can destroy the heater exchange, causing the copper to turn into a liquid form,” he says, “which is then oxidized by chlorine, causing staining and discolored water.”

Stempien says to be wary of algaecide ingredients, too, because some of them contain metals.

Poma concurs, seeing copper staining from algaecides occasionally. “I have learned in the past couple of years that alum can lift copper stains,” he says. “It just turns it back into a liquid state and then can be removed with metal out.”

Derr says that Jack’s Magic Stain IDentification Kit is useful for determining the right treatment for a pool stain. He prefers Hydropure Technologies’ stain removing treatment when he needs it, which he says removes nearly 100% of stains for him when used properly.

“But weekly water testing and balancing of the chemistry is the most important thing you can do to prevent stains and other issues,” Derr says. “Also, keeping debris out of the pool.”

DeRoche’s stain treatment of preference is the Stain Drop system from Haviland, but he also emphasizes how critical water care is for stain prevention. “Healthy water and pretty blue water can be different,” he says. “Stay on track with the LSI scale and monitor the pool surface to be able to identify a possible metal fall out issue as soon as it happens, so it can be taken care of quickly, before anything gets out of hand and you have an entirely stained pool.”

HydroPure Technologies

Product name: Metaltrap Stain Remover
MSRP: $29.99 – $39.99
Product description: Metaltrap Stain Remover is an all-natural, metal removing formula that chemically pulls iron, copper and manganese stains off pool and spa surfaces. Metal stains are less likely to reoccur when this product is used in combination with HydroPure’s Pool Refresh and Metaltrap Pre-Filter products.

Jack’s Magic

Product name: Stain IDentification Kit
MSRP: $14.99
Product description: The Jack’s Magic Stain IDentification Kit is designed to take the guesswork out of removing swimming pool stains. One of the four simple topical tests will identify which product(s) best removes the unique stain, saving both time and money, while providing a treatment that will work.

United Chemical

Product name: Pool Stain Treat
MSRP: $6.49 – $24.99
Product description: Pool Stain Treat lifts and prevents the most stubborn stains, guaranteed. It works on iron and organic stains, is safe for any pool surface and prevents stains from coming back. Two pounds treats up to 20,000 gallons.


Product name: STAIN DROP
MSRP: $4.99 – $44.99
Product description: STAIN DROP products diagnose, remove and prevent future pool stains. The STAIN DROP S.R.V. kit helps pool professionals diagnose which products will most effectively remove a stain. STAIN DROP No. 1 removes iron and organic debris stains, DROP No. 2 removes copper stains and scale and DROP No. 3 oxidizes metal stains for easier removal. STAIN DROP All Purpose and All Purpose XpH provide powerful, long-lasting, broad-spectrum stain prevention.

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Eric Knight