Frequently Asked Questions

Algae

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Q. How many types of algae are there?
A. There are two types of algae – free floating and clinging algae. The clinging type embeds itself into cement, making it difficult to remove. It can be slimy and can cause surfaces to be slippery.

Q. What colour is algae?
A. Depending on conditions, algae can appear in many different colours.  

Q. Why has algae formed in my pool?
A. Algae formation indicates that a regular sanitiser and free chlorine content in the water is not being maintained. Even if a sufficient level is obtained, it may not be enough to kill the algae. Poor water circulation due to poor pool design can also have an effect.
The algae spores may be protected by stale/dead water within the surface. As soon as there is a drop in the free chlorine level, algae growth will accelerate.

Q. How do I kill and remove algae?
A. To kill and remove algae, super chlorination can be carried out for mild algae and shock chlorination for heavy infestations. Heavy chlorination will kill the algae making it very easy to brush off and filter out. Run the pool pump continuously for 24 hours to circulate the water.
Before chlorination, do a water test for calcium and cyanuric acid. If there is a high content of calcium or cyanuric acid, partially empty the pool and dilute with fresh water.

Q. Super chlorination hasn’t removed algae in pool, what to do next?
A. If super chlorination is unsuccessful, place stabilised granular chlorine directly onto the surface.
Algaecides are another option. To avoid staining, a ‘normal’ algaecide should be used (as opposed to a ‘premium’ algaecide) as normal algaecides don’t contain copper – copper may stain the pool surface. However, algaecides should only be used to treat specific areas of algae formation i.e. dead spots caused from poor water circulation.

Blisters/Delamination

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Download Blisters/Delamination Fact Sheet

Q. What causes blisters in pool?
A. Blisters are caused by small pockets of air being trapped between the pool surface and the concrete shell. As the cement cures or the day gets hotter during application, the air expands causing a small void to be formed between the pool shell.

Q. What causes delamination in a pool shell?
A. Large delaminated areas are a result of bonding failure to the shell, which can be caused by:

  • Concrete shell not properly cured
  • Untreated weepers
  • Foreign material not cleaned off concrete shell prior to application
  • Surface improperly prepared
  • Pool took too long to fill (should be filled within 36 hours)
  • Extremities in drying time between areas
  • Pool was left too long without water

Q. How to remove blisters and delamination?
A. If one large area is of concern, it may be treated by draining the pool and drilling two holes in the delaminated area. Fill with an expandable product and then patch the holes.

Calcium Nodules

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Q. What are the raised spots/nodules that are a circular shape on pool surface?
A.  Nodules may result from a hairline crack in the surface making the scale appear long and thin. If there is a void under the surface, calcium hydroxide formed as the cement hydrates, builds up and a mild pressure causes it to leach through the surface. The calcium hydroxide then reacts with carbonate in the water and forms a calcium carbonate nodule.

Q. Does nodule formation depend on water flow?
A. Yes. If the calcium flow through the crack is rapid, it will simply dissolve into the water not forming a nodule. A slow exchange of water causes the water in the void to experience chemical conditions (high pH, high calcium) separate from the rest of the pool. As this solution leaches into the pool water, it solidifies and forms a nodule.

Q. How to remove a spot/nodule from the surface?
A.  Using wet-and-dry sandpaper or a rubbing stone, rub back the nodules.
Another option is to pour acid down a 40mm-conduit pipe directly onto the nodule to then brush it nodule off. In severe cases, the pool must be drained and acid washed.

Calcium Scale

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Q. Why has the pool surface become patchy/blotchy?
A. This can be due to the high pH level causing the calcium in the water to precipitate out of solution and plate onto the surface. It can also be due to calcium levels being out of recommended limits or a higher water temperature.

Q. Why has pool surface become sharp or abrasive to touch?
A. This can be due to the high pH level causing the calcium in the water to precipitate out of solution and plate onto the surface. It can also be due to calcium levels being out of recommended limits or a higher water temperature.

Q. Why is chlorine in pool no longer removing algae?
A. This can be due to the high pH level causing the calcium in the water to precipitate out of solution and plate onto the surface. It can also be due to calcium levels being out of recommended limits or a higher water temperature.

Q. How to remove patchiness and blotchiness on pool surface?
A. If scale hasn’t been on the surface for too long, lower the pH to between 6.5 and 6.8 (using hydrochloric acid). Leave at this level for approximately 1 week and brush the affected areas over the duration to remove the scale. Take a water test and balance accordingly. Monitor the surface texture of the pool daily. If the surface becomes rough over exposure may occur. To prevent over exposure, increase the pH with pH Increaser as soon as excessive roughness is detected.

After performing this procedure, it is imperative that calcium levels in the water are returned to recommended levels (200-250ppm).  Failure to do so could cause excessive acid demand which inturn will weaken the surface and may lead to other problems.

If scale has been on the surface for a number of months then the pool will most likely have to be drained and acid washed, then filled up and re-balanced. 
Experienced pool technicians may add acid (10-15L for average 50,000L pool) to the pool the day before it’s drained to soften the calcium.  The pool is then drained and using a high pressure cleaner, the calcium is water blasted off.  The pool is then refilled and rebalanced. 

To avoid future calcium scale occurrences, maintain Cal-Stop in your pool water.  This can be achieved by purchasing a bottle of Cal-Stop from your local pool shop every 6 months.  Cal-Stop keeps calcium in solution even if the pH level does increase.  If your local pool shop doesn’t stock Cal-stop then please call River Sands on (07) 3412 8111 Brisbane callers or 1800 077 744 Toll Free for supplier near you.

Q. How to remove sharp abrasive texture off pool surface?
A. If scale hasn’t been on the surface for too long, lower the pH to between 6.5 and 6.8 (using hydrochloric acid). Leave at this level for approximately 1 week and brush the affected areas over the duration to remove the scale. Take a water test and balance accordingly. Monitor the surface texture of the pool daily. If the surface becomes rough, over exposure may occur. To prevent over exposure, increase the pH with pH increaser as soon as excessive roughness is detected.

After performing this procedure, it is imperative that calcium levels in the water are returned to recommended levels (200-250ppm).  Failure to do so could cause excessive acid demand which inturn will weaken the surface and may lead to other problems.

To avoid future calcium scale occurrences, maintain Cal-Stop in your pool water.  This can be achieved by purchasing a bottle of Cal-Stop from your local pool shop every 6 months.  Cal-Stop keeps calcium in solution even if the pH level does increase.  If your local pool shop doesn’t stock Cal-stop then please call River Sands on (07) 3412 8111 Brisbane callers or 1800 077 744 Toll Free for supplier near you.

Q. Sharp abrasive texture on pool surface for over three months, how to remove?
A. If scale has been on the surface for a number of months then the pool will most likely have to be drained and acid washed, then filled up and re-balanced.  Experienced pool technicians may add acid (10-15L for average 50,000L pool) to the pool the day before it’s drained to soften the calcium.  The pool is then drained and using a high pressure cleaner, the calcium is water blasted off.  The pool is then refilled and rebalanced. 

To avoid future calcium scale occurrences, maintain Cal-Stop in your pool water.  This can be achieved by purchasing a bottle of Cal-Stop from your local pool shop every 6 months.  Cal-Stop keeps calcium in solution even if the pH level does increase.  If your local pool shop doesn’t stock Cal-stop then please call River Sands on (07) 3412 8111 Brisbane callers or 1800 077 744 Toll Free for supplier near you.

Q. Sharp abrasive texture on pool surface for over three months, how to remove?
A. If scale has been on the surface for a number of months then the pool will most likely have to be drained and acid washed, then filled up and re-balanced.  We recommend you contact your experienced pool technician to conduct this procedure.
To avoid future calcium scale occurrences, maintain Cal-Stop in your pool water.  This can be achieved by purchasing a bottle of Cal-Stop from your local pool shop every 6 months.  Cal-Stop keeps calcium in solution even if the pH level does increase.  If your local pool shop doesn’t stock Cal-stop then please call River Sands on (07) 3412 8111 Brisbane callers or 1800 077 744 Toll Free for supplier near you.

Calcium Levels

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Q. Why has pool water become cloudy?
A. This is due to high calcium levels – if excessive amounts of acid have been added to the pool, it causes calcium to be drawn out of the cement.
If it is within the first 8 weeks after installation, the pool interior is curing and calcium is a by-product of cement curing.

Q. How to clear cloudy water? 
A. Partially drain pool to dilute the high calcium content and bring back to between 200 – 250ppm. Repeat this until desired levels are achieved. Rebalance Total Alkalinity, pH and add Cal-Stop.

High Acid Demand

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Q. Why does pool require excess amounts of acid - greater than 0.8 litre per week (after first 6 weeks)?
A. This can be due to excess calcium levels making it extremely difficult to lower pH. It can also be that the Total Alkalinity is too low or algae is present in pool.

Q. Why are pH levels difficult to control in pool? 
A. There can be excess calcium levels (<350ppm) making it extremely difficult to lower pH.
It can also be hard to control pH levels as the Total Alkalinity is too low or there is algae present pool.

Q. How to prevent pH levels from fluctuating?
A. To prevent pH levels from fluctuating, reduce calcium to between 200-250ppm – partially drain pool and dilute with fresh water. Repeat dilution until recommended levels are achieved. Rebalance Total Alkalinity, pH and add Cal-Stop.
It is also recommended the Total Alkalinity is increased by adding Total Alkalinity increaser to 100-200ppm.

Q. How to reduce amount of acid required in pool?
A. Reduce calcium to between 200-250ppm – partially drain pool and dilute with fresh water. Repeat dilution until recommended levels are achieved. Rebalance Total Alkalinity, pH and add Cal-Stop. Increase Total Alkalinity by adding Total Alkalinity increaser to 100-200ppm.

Holes in Quartzon surface

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Q. Why have areas in pool interior become dislodged? 
A.   Holes in the pool surface can be created from picking out a piece of aggregate or scraping a nodule off the surface, causing a larger section to come out.
Other causes can be from water blasting as small amounts of product can become dislodged.

Inconsistent Colour (walls to floor)

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Q. Why is the floor of pool a different colour to the walls?
A. This can be due to over exposure of the floor, too much time left between finishing walls and beginning the floor, or the floor was trowelled at ninety degrees to the direction the wall was trowelled.

Q. Why is the pool floor darker than the walls?
A. This can be due to over exposure of the floor, too much time left between finishing walls and beginning the floor, or the floor was trowelled at ninety degrees to the direction the wall was trowelled.
If the mix used on the floor was drier, it can affect the colour and if two separate batches were used, the colour will be affected.  

Q. How to correct pool surface so floor and wall colour are the same?
A. You should contact your experienced pool contractor to complete the below task.
Acid wash the pool again applying particular attention to blending in the floor to the walls.

  • It may be possible to expose more of the coloured aggregate in the walls thereby darkening them and providing a better match, and/or;
  • Polishing the joint line and the floor. Polishing slightly lightens the surface as glaze is removed from the coloured aggregate.

After performing either of these procedures it pays to pressure wash the entire surface, as this will remove excess oxide. Doing so helps to even out colour variations.
Whilst it may not be possible to completely eliminate all the colour variation, the solution described above will certainly help. Over time the discrepancy will reduce of its own accord as the cement sits immersed in water and fully hydrates.

Q. How to prevent producing two different colours on floor & wall when acid washing?
A. Pay particular attention when acid washing that acid is not allowed to sit on the floor of the pool. Ensure that a wet edge is maintained at all times.
Also consider:

  • Ensuring adequate trowel hands are available.
  • Reducing the length of the wet edge by working across the pool rather than doing the walls first then the floor.
  • Avoiding cross trowelling at joins, i.e. when joining the walls to the floor, attempt to trowel the floor in the same direction as the walls.
  • Ensure batches of stock are mixed evenly from different production dates.

Q. How to control depth of pool surface when acid washing?
A. Pay particular attention when acid washing that acid is not allowed to sit on the floor of the pool. Ensure that a wet edge is maintained at all times.
Also consider:

  • Ensuring adequate trowel hands are available.
  • Reducing the length of the wet edge by working across the pool rather than doing the walls first then the floor.
  • Avoiding cross trowelling at joins, i.e. when joining the walls to the floor, attempt to trowel the floor in the same direction as the walls.
  • Ensure batches of stock are mixed evenly from different production dates.

Inorganic Stains

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Q. What has caused brownish colour on pool surface where salt sits to appear?
A.  Salt stains result when salt is added to the water but the surface is not brushed sufficiently to prevent the salt from settling on the surface.

Q. What has caused reddish-brown stains on pool surface to appear?
A. Rust stains occur when metal settles on the surface and corrodes. If the stain appears to be coming from something in the surface then some metallic particles may have contaminated the render as it was being applied.
A high content of Total Dissolved Solids (TDS) can also cause metal staining.

Q. What has caused metal stains on pool surface to appear?
A. Metal stains commonly occur from hair clips or pieces of jewellery that are left to sit on the surface.
A high content of Total Dissolved Solids (TDS) can also cause metal staining.

Q. What has caused rust spots on pool surface to appear?
A. Small rust spots on the surface may also be the result of work conducted near the pool whereby particles of metal have found their way into the pool.
A high content of Total Dissolved Solids (TDS) can also cause metal staining.

Q. Can reinforcement steel in pool cause metal stains?
A. Corroding reinforcing steel can cause metal stains through to the surface.

Q. How to remove reddish-brown stain from pool surface?
A. In most instances, sprinkling citric acid onto the mark should remove it. If the staining is on a vertical surface, the citric acid can be placed in a stocking and allowed to sit on the mark.
If there are too many marks for localised treatment, lower the pH down to 6.8, reduce the chlorine level down to between 0.5 and 1ppm and sprinkle citric acid on the water’s surface, concentrating on contaminated areas. Allow the pool to sit for 12-24 hours. 2-4 kg per 50,000L of pool water is an acceptable dosage rate depending on the severity of the marks.

Q. How to remove brownish salt stains from pool surface?
A. In most instances, sprinkling citric acid onto the mark should remove it. If the staining is on a vertical surface, the citric acid can be placed in a stocking and allowed to sit on the mark.
If there are too many marks for localised treatment, lower the pH down to 6.8, reduce the chlorine level down to between 0.5 and 1ppm and sprinkle citric acid on the water’s surface, concentrating on contaminated areas. Allow the pool to sit for 12-24 hours. 2-4 kg per 50,000L of pool water is an acceptable dosage rate depending on the severity of the marks.

Q. How to remove rust spots from pool surface?
A. In most instances, sprinkling citric acid onto the mark should remove it. If the staining is on a vertical surface, the citric acid can be placed in a stocking and allowed to sit on the mark.
If there are too many marks for localised treatment, lower the pH down to 6.8, reduce the chlorine level down to between 0.5 and 1ppm and sprinkle citric acid on the water’s surface, concentrating on contaminated areas. Allow the pool to sit for 12-24 hours. 2-4 kg per 50,000L of pool water is an acceptable dosage rate depending on the severity of the marks.

Organic Stains

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Q. What is the coloured stain that has appeared on pool surface?
A. This stain can appear in many different shapes and colours (yellow, green, black, brown). It is produced as a result of decaying organic material (e.g. leaves) that settles on the surface. It can also be caused from free-floating algae which bonds with calcium particles to then plate out the surface.

Q. How to remove coloured stain on pool surface?
A. Depending on the severity of the stain, raising the free chlorine level (to approximately 5ppm) may be sufficient to remove the stains. However, if the stain is severe then sprinkle stabilised granular chlorine on the surface and allow to sit until stain has been removed.
If chlorine doesn’t remove the stain then the citric acid method should be tested – citric acid is a very effective oxidiser and works well to break down stains.
If the stain is greater than 30cm, treat as calcium scale – refer to calcium scale FAQ’s.

Rough Spots

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Q. Why are area/s of pool surface rough to touch?
A.  If the area is darker, it may have been overexposed. The acid may have been left too long when exposing or maintenance procedures have been poor.

Q. What is the cause of rough areas on pool surface that resemble streaks and appear to flow downwards?
A. If in patches, the area/s usually look slightly darker in colour when compared to the rest of the surface. Darker areas have been overexposed which can be a result of:

  • Acid being left too long on the surface during the acid wash/acid bath causing an excess of cement to be washed away which leaves remaining aggregate protruding from cement (over exposure of aggregate).
  • Acid must always be diluted when added to pool water. If it’s not and is added to pool water, the acid will sink to the bottom and overexpose the surface (acid is heavier than water).

Note: If rough patches are lighter or dull in colour, refer to Calcium Scale questions.

Q. How to repair areas on pool surface that are overexposed?
A. Areas of overexposure need to be sanded down using either wet and dry sandpaper or a rubbing stone. Be careful not to over rub the spot causing a lightening of the surface. Make sure to test first on a small unobtrusive area.

Ensure that any acid to be added to the pool is always diluted.

Small Cracks

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Q. What are the small cracks in new pool surface?
A. These small cracks, referred to as hairline cracks, are plastic shrinkage cracks that appear in the surface of cement renders and slabs within a few hours of placing, sometimes after final trowelling and frequently before trowelling.
They rarely impair strength of the work, but can commonly form a tree branch pattern, a network of ‘mudcracks’, or sometimes tend to be straighter, in a pattern across the surface.

Q. What causes small cracks or hairline cracks to appear in pool surface?
A. Small hairline cracks can appear in plaster due to normal shrinkage or flexing of the supporting structure and should not be considered a deficiency.
They can also be a result of taking too long to fill the pool (should be filled within 36 hours) or the pool was finished on a hot, dry or windy day.

Q. How to remove/fill hairline cracks in pool surface?
A.  Small hairline cracks typically heal themselves as the cement fully hydrates. However, if the crack remains visible try rubbing the wet and dry sandpaper.