Last Updated: June 19, 2022

Pool Rust Stain Removal

Written By: Pool Care Guide

Pool waters are best enjoyed when crystal clear. But what happens when you spot rust stains on the pool’s interior walls? What causes pool rust, and how do you get rid of the rust?

If you have a plaster pool, it will stain easier than vinyl pools, but the latter makes it easier for minerals to accumulate and stain it. Fiberglass pools retain their looks for longer, but they are more likely to scratch and look stained than plaster or vinyl pools.

What Causes Rust Stains in Pools?

There are several causes of rust stains in swimming pools. Herein are the five most common causes of pool rust and ways of dealing with them.

Metallic Objects

Metallic objects in your pool could be hairpins, nails, toy cars, bottle caps, or metal cans. Such metals rust within a day if they settle in the pool and stay undisturbed. The rusting period might be shorter if these items sit in acidic pools.

The ideal solution is to remove metal objects as soon as you spot them. Always keep any metallic items away from the pool area.

Encourage pool users to remove their hair clips and pins before swimming.

Iron Oxidation

If the pool water contains metals, water oxidation will happen, causing several tiny rust spots in the pool.

Oxidation mainly occurs in cases where pool owners use iron pipes to fill up their pools, or the source of their pool water is a well.

Adding an iron remover additive immediately after filling your pool will help prevent such rust stains.

Organic Materials

It isn’t uncommon for organic materials like leaves, grass, and pine cones to drop and sit on the surface of your pool. After a while, these materials will decay, leaving rusty spots in the pool.

You can prevent such rust stains by removing organic materials as soon as you spot them. Frequently cleaning your pool is an excellent prevention method in this case.

Rebar Rust Stains

Rebar is the intersecting metal shafts under the plaster of your pool. If there isn’t enough concrete coverage for the rebar, it will quickly damage, causing stains to form. If left untreated, extensive corrosion will occur, leading to structural failure.

An ideal way of solving this issue is appropriately encasing the rebar in concrete. The alkalinity of concrete helps offset oxidation, reducing rust formation.

Soluble and Colloidal Iron

The well water you’re using to fill up your pool may contain soluble and colloidal iron, which will rust after getting into contact with air.

Thankfully, adding chlorine or other chemicals to oxidize iron will help prevent this rust formation.

Five Ways to Eliminate Rust Stains from Your Pool

Below are five ways of eliminating rust stains from your pool.

Use Vitamin C Tablets To Remove Tiny Rust Stains

Unknown to some pool owners, vitamin C supplements can remove tiny rust spots from pools.

Rub vitamin C tablets over the stain spots and wait for the magic to happen. The ascorbic acid will dissolve rust almost instantly.

This method is only ideal in cases where the rust stains aren’t extensive. If the rust stains occupy a larger surface area, rubbing vitamin C tablets on each spot may be time-consuming.

A quick alternative is crushing the tablets and then sprinkling the powder over the stains. You may need to brush it off afterward.

Embrace the Sock Method

Most pool owners have probably heard about the sock method as an effective technique to remove rust stains. But do you know how to use this method?

First, wear protective eyewear and gloves because you’re about to deal with harsh chemicals. Once your safety is in check, take a clean sock and add a cup of granular acid such as sodium bisulfate, also known as dry acid, to the sock.

You can also use ascorbic acid (vitamin C tablets) in place of sodium bisulfate. Tie the sock tightly to prevent the acid from getting out.

If the stains are far down at the bottom of the pool that your hands can’t reach, you can use a pool pole to lower the sock and hold it over the stains.

Do this for about five to fifteen minutes, checking often to see the results. Be careful not to leave the sock on the stains for too long since it may lead to a reverse stain. A reverse stain is where the previously rusted spots become brighter than the surrounding areas.

Adopt the Acid Washing Technique

Sometimes, the rust stains may occupy a larger surface area of your pool or appear randomly all over the pool. Applying the above techniques may be too tiring and will consume a lot of time.

In this case, acid washing the entire pool could be your ideal rust stain removal technique. The process requires draining the pool, making it more of a professional job than a DIY project.

This acid wash technique may be costly since you’re unlikely to be able to do it yourself. However, it’s worth it for those pools with rust stains all over the place. After removing all the rust stains, the acid washing method will give your pool its brand new look back.

But for the DIY enthusiasts, you can still use a no-drain acid wash technique to remove the rust stains.

Lower the swimming pool’s pH and scrub off the stains. Use any pH reducers available in most home improvement and pool supply stores. Applying such chemicals will make the pool water quite acidic. Scrub with a pool brush after a while to eliminate all the stains.

Buy a Jandy Pool Stain Remover

The Jandy stain removal master is another acid washing technique for removing stain spots in small areas. This tool works by drawing off the muriatic acid in a container attached to its deck. It then delivers the acid to the pool surface to remove rust stain spots.

Note that muriatic acid can be harsh on vinyl. So, if you have a vinyl pool and you must use this tool, consider substituting the acid with either chlorine or liquid algaecides.

The Jandy stain remover may lead to a reverse stain like the sock method if left for too long over the stains. To avoid this problem, hold this tool over one stain spot for ten seconds maximum before moving to the next spot.

Do a Plaster Repair To Remove Recurring Rust Stains

Consider plaster repair if you have a plaster pool and the rust stains keep appearing on the same spot even after applying the above methods. It could be the rebar rusting, which may ultimately worsen the condition of the pool if left untreated for long.

The rebar should have at least four to five inches of coverage for the pool’s structure to stay sound over time. However, problems begin when the rebar stays within one inch of the pool’s surface, getting wet and causing rusting to the surface. Applying any of the above rust removal methods will only remove the rust stains for a short time before they reoccur.

You may need to hire a professional for the plaster repair or do it yourself. Drain the water until the area you want to repair is exposed. Then, using a diamond blade and four-inch grinder, cut out the repair section, ensuring you cut through the rebar.

Use a rubber sealant to seal the rebar ends until they dry off, then use hydraulic cement to fill up the hole. Once the hydraulic cement dries off, you can use a pool plaster to top the filled hole.

Finally, refill the pool to enjoy your swims again without the rust stains getting in the way. There are also various stain erasers and eliminators to remove pool rust stains as long as you identify the type of pool surface you have.

Final Thoughts

Pool rust stains could lead to costly pool repairs if you don’t remove them as soon as possible. With the above techniques, you can quickly bring back the pool to an excellent state, as long as you understand the cause of the rust.

Never use acid removers on a vinyl pool as it may damage it further. Instead, opt for alternatives like chlorine or seek a professional’s help to be sure.

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