The cheap, effective method most pool shops won’t tell you about
Metal stain removal is one of the most common pool problems Australian homeowners face. If your pool has developed dark, greenish, or bluish stains across the walls, floor, or waterline — chances are you’re dealing with metal staining. Specifically, copper staining. And the good news is you don’t need to drain your pool or spend hundreds on an acid wash to fix it. Not sure if you have metal staining? Read our guide on how to identify pool staining here.
This guide walks you through a complete metal stain treatment from start to finish using products available at any Australian pool shop, for a fraction of what you’d pay a professional.
What Is Metal Staining?
Metal staining occurs when dissolved metals in your pool water bind to pool surfaces. The most common culprit in Australian pools is copper, which typically comes from:
- Copper-based algaecides
- Old copper pipe fittings or heat exchangers
- Pool ionisers
- Bore or tank water with high copper content
Other metals that can cause staining include iron (which leaves reddish-brown or dark stains) and manganese (which leaves black or purple staining).
How to Identify Copper Staining
Copper staining is distinctive once you know what you’re looking for:
- Colour: Black, dark green, or blue-green
- Location: Can appear anywhere — walls, floor, steps, or spread across the entire pool surface
- Pattern: Often patchy or streaky, following water circulation patterns
If your stains are reddish-brown, you’re likely dealing with iron. The treatment process below works for both.
What You’ll Need
Before you start, grab these products from your local pool shop:
- Strip test kit (for testing chlorine levels quickly)
- Chlorine remover (sodium thiosulphate) — approximately 500g depending on pool size and chlorine level
- Multi stain remover — 1–3kg depending on pool size (more on dosage below)
- Filter aid and metal remover — 300g (media/sand filters only — do NOT use with cartridge filters)
- Chlorine (granular or liquid) for superchlorination at the end
- Alkalinity buffer (sodium bicarbonate)
- A pool broom
Approximate cost: $40–$80 AUD depending on what you already have at home. Compare that to $400–$800+ for a professional drain and acid wash.
Step-by-Step Metal Stain Treatment
Step 1: Clean Your Filter
Before you do anything else, give your filter a thorough clean.
- Sand/media filter: Backwash until the water runs clear
- Cartridge filter: Remove cartridges and hose them down thoroughly
Starting with a clean filter means it can do its job properly at the end of the treatment. Don’t skip this step.
Step 2: Test Your Chlorine Level
Use a strip test to check your current chlorine level. You need to know this before adding chlorine remover.
Strip tests are recommended here over liquid test kits — they’re faster and accurate enough for this purpose.
- If chlorine reads high (above 1 ppm): You’ll need to add chlorine remover in the next step
- If chlorine reads zero or very low: Skip the chlorine remover and go straight to Step 4
Step 3: Remove the Chlorine From the Pool
This is the most critical step. The multi stain remover will not work effectively if there is chlorine present in the water — the chlorine will neutralise it before it has a chance to work.
With the pump running, spread approximately 500g of chlorine remover (sodium thiosulphate) evenly around the pool. The exact amount will depend on your pool size and how high the chlorine reads.
- Chlorine remover acts quickly — it will begin neutralising chlorine within minutes
- Continue strip testing every few minutes until the chlorine reads zero
- Add more chlorine remover in small doses if needed until you get a zero reading
Do not move to the next step until your chlorine is completely gone.
Step 4: Apply the Multi Stain Remover
Once your chlorine reads zero, turn the pump off.
Now apply your multi stain remover. The product label will typically recommend 1kg per 50,000L of water — but here’s the trick most people don’t know:
Overdose it.
For an effective stain treatment, use 1–3kg regardless of what the label says. More product means better penetration into the stain and a higher chance of full removal in a single treatment. Being conservative with the dose is the most common reason stain treatments fail.
Apply the multi stain remover by:
- Targeting heavily stained areas directly
- Spreading the remainder evenly around the rest of the pool
The product will dissolve and begin working immediately.
Step 5: Leave the Pump Off for 24 Hours
This is non-negotiable. The pump must remain off for a full 24 hours to allow the stain remover to work without being diluted or moved by circulation.
Resist the urge to check on it every hour. Just leave it.
Step 6: Broom the Pool, Add Filter Aid, and Superchlorinate
After 24 hours, it’s time to finish the job.
- Broom the entire pool — walls, floor, and steps. This dislodges any loosened staining and residue from the stain remover and gets everything into suspension so the filter can pick it up.
- Add filter aid and metal remover — add approximately 300g to the pool water. ⚠️ Important: Only use filter aid and metal remover if you have a sand or media filter. Do NOT add this product to a pool with a cartridge filter — it will clog and damage your cartridges.
- Superchlorinate the pool — add a full superchlorination dose of chlorine (granular or liquid) to shock the water back to a safe level. Follow the dosage on your chlorine packaging based on your pool size.
- Run the pump for 24 hours straight — this circulates everything through the filter and clears the water.
Step 7: Clean the Filter Again
After the 24-hour pump run, clean your filter again.
- Sand/media filter: Backwash thoroughly
- Cartridge filter: Remove and hose down the cartridges
There will be a significant amount of debris and residue caught in the filter from the treatment — a good clean here makes a real difference to water clarity.
Once done, return your system to its normal automatic timer settings.
Step 8: Get a Professional Water Test
After this treatment, your water chemistry will be off. Specifically:
- pH will be low — the treatment process is acidic
- Chlorine may need topping up
- Alkalinity will likely need buffering
Take a water sample to your local pool shop and ask for a full water analysis. They’ll give you an exact breakdown of what needs adjusting and how much of each chemical to add to bring your pool back to the Australian Standard for pool water balance.
Don’t skip this step — swimming in chemically unbalanced water is uncomfortable and can damage your pool equipment and surfaces over time.
Why This Method Works Better Than Draining
Most pool companies will quote you for a drain and acid wash when you have significant staining. This involves:
- Fully draining the pool (expensive, wastes thousands of litres of water)
- Acid washing the surfaces (harsh on pool finishes, especially fibreglass)
- Refilling and full chemical restart
Total cost: $400–$1,500+ depending on pool size and location.
The multi stain remover method achieves comparable results in most cases for under $100 in products and a weekend of your time. For the average Australian homeowner dealing with copper or iron staining, there’s simply no reason to drain the pool first.
The only scenario where draining becomes necessary is if staining is extremely severe, has been left untreated for many years, or is caused by structural issues with the pool surface itself.
Quick Reference Summary
| Step | Action | Pump |
|---|---|---|
| 1 | Clean filter | Running |
| 2 | Strip test chlorine | Running |
| 3 | Add chlorine remover, test until zero | Running |
| 4 | Apply 1–3kg multi stain remover | OFF |
| 5 | Wait 24 hours | OFF |
| 6 | Broom pool, add filter aid, superchlorinate | Running |
| 7 | Run pump for 24 hours | Running |
| 8 | Clean filter, return to auto | Auto |
| 9 | Professional water test | Auto |
Frequently Asked Questions
Will this work on all types of pool staining? This method is most effective on metal staining — copper, iron, and manganese. It is not designed for organic staining (leaves, algae) or structural surface damage. If you’re unsure what type of staining you have, take a photo to your local pool shop for identification.
Can I do this treatment in winter? Yes, though the process may take slightly longer in cold water. The stain remover is less reactive at low temperatures. Summer is ideal, but the treatment is effective year-round.
My stains didn’t fully disappear — what now? Repeat the treatment. Stubborn staining sometimes requires two rounds. Make sure you’re using enough multi stain remover (err on the side of more, not less) and that your chlorine is genuinely at zero before applying it.
Is it safe to swim after the treatment? Not until you’ve completed the full process, run the pump for 24 hours, and had your water professionally tested and rebalanced. Once your pool shop gives you the all-clear on water chemistry, it’s safe to swim.
What if I have a saltwater pool? The process is the same. Turn your chlorinator off during the treatment so it doesn’t regenerate chlorine while you’re trying to keep levels at zero.
Have a question about pool staining not covered here? Drop it in the comments below and we’ll answer it.