Ahhh rust stains, those annoying little spots (or patches) of brown that seemingly appear from nowhere and they just ruin the crystal blue color of your pool, really, major eyesores. Although we’ve already talked about how to identify and treat different types of pool stains, today we’re going to focus on rust stains due to popular demand!
Sources of pool rust stains
Before we start with how to remove rust stains, let’s first go through the different sources of rust stains so that we can prevent the stains from coming back in the future after we’ve dealt with the stain.
- Rust from Metal Objects - Things like bottle caps, hairpins, metal buttons and the like that somehow find their way to your pool will start to rust in a day or so after falling in, especially if they lie undisturbed. These are basically superficial stains that once treated will be gone forever.
- Recurring Rust Stains - Initially, many people will just think that this is just rust from metal objects falling into the pool that got vacuumed out, but once the stain has been treated, lo and behold, after a few days, the stain is back at the same exact spot! These types of stains are usually caused by small cracks on your pool surface and water leeching into the rebar below. This type of stain is also called “Concrete Cancer” because it will keep recurring and it will gradually become worse over time at an increasing rate. If you discover this type of stain, it’s advisable to contact a pool professional to do some repairs on your pool to seal up the cracks.
- Metals in pool water oxidising - even if you’re meticulous in cleaning your pool, metals still can get into your pool from the source water especially if your area uses well water or if the pipes feeding your pool water are made out iron.
- “Rust Plating” - This happens with the improper use of copper-based algaecides. Usually this happens when high levels of chlorines (from shocking or from the return jets if you have a salt water chlorinator) react with the copper from copper-based algaecides. More of removing this later, but as a prevention tip, simply avoid high chlorine concentrations while using copper-based algaecides.
Pool Rust Stain Removal Techniques
Here are some of the techniques we use here at Mr Pool Man to get rid of rust stains from our pool.
Using Vitamin C Tablets
With the pandemic, every household should have some vitamin C on hand, and if you’ve gone overboard with stocking up on vitamin C then this is the perfect use for them! Using vitamin C tablets are perfect for spot stain removals from metal objects. For tiny rust spots, simply take a vitamin C pill and rub it on the spot and you should see instant results just like magic! How does this work? Well, Vitamin C tablets are basically ascorbic acid, which is quite acidic, and the acid melts away the rust! Simple and easy solution for small stain spot removal.
Note: Make sure that you have the traditional Vitamin C tablets and not the new-fangled non-acidic sodium ascorbate Vitamin C tablets that are starting to become popular as those don’t do anything for stains, remember, it’s the acid doing the job!
The “Sock Method”
If you’ve been around pools for a while then you’ve probably already heard of this method of removing rust stains. This is perfect for large patches of rust stains or for those on the bottom for your pool where it’s just not possible to go down and rub off those stains by hand. You’ll need a handful of vitamin C tablets (again, regular vitamin C) and an old sock (MAKE SURE THE SOCK IS CLEAN, SERIOUSLY). So if the washing machine pixies have stolen one of your socks, don’t throw the unmatched sock away, store them for future use.
Take a handful of vitamin C and stuff it into the stock and tie it off tightly. Give it a couple of good whacks to crack and crush the pills inside so that they’ll be released into the water much easier. Use the sock as like a sponge to scrub off patches of rust stains on steps and on your water lines. For deeper stains, you can tie the sock to the end of your telepole and use that in place of your brush head. Hold the sock against the stain for a couple of seconds for the acid to eat through the stain and then proceed to brush it with your pool brush, this should easily take out the stain.
No Vitamin C Tablets? No Problem!
Have rust spots that you want to take out but vitamin C is at a premium? Then no problem, you can use some Zodiac pH down tablets in place of vitamin C tablets. Zodiac pH down tables are made with Sodium Bisulphate which is basically an acid and works just as well as vitamin C on rust stains! Just be careful and use appropriate protection like gloves and don’t touch your eyes without washing your hand as sodium bisulfate is a lot more corrosive than vitamin C.
Acid Washing your Pool
If there are rust stains all over your pool and spot removal doesn’t seem like a good use of your time then acid washing is one of the quickest ways to bring out the natural color of your pool and remove widespread rust staining. We don’t have a way to DIY acid washing your pool since that requires draining your pool and that’s best left for pool professionals to do it.
What we do have for you is a way to do a no-drain acid wash which you can do by yourself! It involves lowering your pool’s pH levels down to an acidic state, let it eat through the stains and give it a thorough brushing. We’ve outlined the whole process in our swimming pool hack: no-drain acid wash guide here!
Using Zodiac All-in-one stain remover
While DIY methods work well, it’s always good to know that there are ready-made solutions that are tailor-made to deal with rust stains and one of those solutions is the Zodiac All-in-one stain remover. This stain remover is made out of 50/50 Oxalic Acid and Citric Acid making it perfect for pool use. To use the Zodiac All-in-one stain remover, turn off your filtration system to allow the stain remover to settle near the stains. Liberally sprinkle the stain remover at the spots that you want treated and leave it overnight. Bush the spots in the morning and that should take care of your stain problem! After brushing, run your filtration system normally to catch any dirt that you’ve dislodged from your brushing.
Rust stains in your pool are not only eyesores but they can be symptoms of something else! Deal with rust stains as soon as you spot them and observe if they come back to find out what exactly is causing it to prevent them from ever coming back again!
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Happy swimming :)