Black Pool?

If your pool water is black then this is an extreme case of algae. A large dose of chlorine and acid will be required. Use less in fibreglass and vinyl pools, as they can stain easily. If you have black spots on the walls then this is another form of algae known as black spot. It is often caused by a high pH (your pool needs acid). It is hard to remove. The pH has to be kept at about 7.0 and the pool broomed regularly for about 2 weeks. An algaecide like Tropiclear or LoChlor will help this process.

In older pools a stain can occur that will turn the floor or walls black in colour. This not an algae – to check run your hand or foot over a section of black. If it is slimy and smooth you have algae, if it is rough and cannot be moved by brush it is a stain. Black staining can occur from excessive copper levels, which is predominant in older marblesheen pools. Whenever a black stain appears add a few litres of acid to the pool to bring the pH back down to just above 7.0. The stain should disappear. If any remains after 24 hours a stain remover for metals will remove the rest.

What is PH?

pH stands for Potential of Hydrogen and is a measure of the acidity of a solution, in our case pool water.

The pH is a measure of the Acid level in a pool. On a scale of 1 to 14 it goes from Acidic (1) to Basic (14). A pH of 7 is for neutral water. The recommended Ph for a swimming pool or spa is 7.2 to 7.6. This is controlled by adding acid to lower the pH or Soda Ash to raise it. Buffer actually raises the alkalinity but as a by-product it will also raise the pH.

Concrete, pebblecrete, marblesheen and concrete pools have a tendency to be too basic and require acid regularly. Fibreglass and vinyl pools will have a tendency to be too acidic and may require soda ash occasionally. This is due to the surface of the pool. For more information see Alkalinity.

An incorrect pH in heated pools or spas can lead to corrosion of heater elements, seriously shortening their life expectancy. This is why we now recommend Nature 2 (pH neutral) instead of Bromine (acidic/corrosive) in spas.

If your pH gets too low, the water becomes acidic and this can result in swimmers getting sore eyes.

If your pH gets too high it allows algal growth and does not let the chlorine sanitise the water properly.

Hydrochloric Acid is the chemical term for the acid used however when in this weaker form it is also called Muriatic acid. Various brands have labelled it as pool acid, ph down and ph decreaser.

What is Alkalinity?

Alkalinity is a measure of the amount of alkaline material in the water, usually present as bicarbonates, pH carbonates and hydroxides. The amount of alkali in the water will determine how easy it is for changes in pH to occur.

The Alkalinity or temporary hardness is what prevents a change in ph (otherwise known as a buffer) in your pool. The recommended level is approximately 100ppm. To raise your alkalinity add Buffer (Sodium Bicarbonate) and to lower it use Soda Ash (Sodium Carbonate). Acid is often used to lower alkalinity but it will not reduce the levels it will just appear to change them due to the method of testing used, but it will lower your pH significantly.

The pH is critical for water balance and by increasing your alkalinity you can buffer the pH in your pool so that it won’t fluctuate as easily. Just remember that when adding Buffer to a swimming pool to increase the alkalinity, it will also increase the pH, so you may need to add more acid.

One of the biggest influence on your pH and Alkalinity is the surface of your pool. Concrete, marblesheen and aggregate pools have a surface high in lime and calcium carbonate. Leaching from this surface will increase both the alkalinity and pH. This is why you will use more acid in a concrete pool. To help prevent this new concrete or pebblecrete pools should be dosed with 4-8kg of buffer when first filled. This will cause the surface to ‘seal’ reducing leaching. In fibreglass, vinyl or painted pools the sealed surface means that there is little influence on the water chemistry. This will result in usually lower pH and Alkalinity level. This is not a problem and is why Buffer is not really required in smooth surface pools.

An important thing to note is that when you adjust your alkalinity you will affect your pH. If you try our free software which uses the Langelier index to balance water you will discover that the alkalinity has a fairly minor impact on water balance in comparison to your pH. With a pH between 7.2 and 7.8 you can have an alkalinity anywhere between 30 and 300 without a problem. Tap water is usually around 30-40 which is why buffer is not regularly required in most pools.


Discoloration of the walls of a swimming pool is due to incorrect water balance.

If the walls are slimy to touch then you have algae. This will need to be killed with a large dose of chlorine. See Algae help for more information.

The other alternative is a stain. Stains are often caused by various minerals or metals falling out of the water due to an incorrect water balance. The first step is to check your water balance. In most cases the pH is the problem. Black copper stains or brown manganese or iron stains both predominantly occur when the pH is high. Reducing the pH in most cases will remove the stain back into solution. If you have problems with re-occurring black stains, get your copper levels tested and do not use algaecides as they contain high levels of copper. This is common in many ioniser based systems as they use Copper/Silver electrodes. This is one reason why ionisers are not sold in every pool shop.

Salt chlorinators, due to the sudden change in pH they create, can often produce brown iron/manganese stains, which will start opposite the return jet. Again, adjusting your pH will solve this problem.

Once the water balance is correct any remaining stains can be corrected using a stain remover or metal remover.

Staining is very common in vinyl and fibreglass pools. Brown dusty stains on the liner are best removed with an organic acid stain remover.

Salt Water

There are two reasons you may have salt water in your pool. Many people have a preference to swimming in salt water and this can be achieved by merely adding up to 10 (25kg ea) bags of salt in a 50,000 pool. The most common reason however is for use with a salt water chlorinator.

Salt is actually Sodium Chloride. Salt Chlorinators work by breaking up the salt molecules and releasing the chlorine into the water. This is how they chlorinate your pool for you. They do require some maintenance but they save the day to day manual dosing.

There is no such thing as too much salt in a pool. While tap water has a very low salt level [0.03-0.15%], many ocean pools, such as those operated by local councils, are successfully treated and chlorinated with levels up to 3.5% or 35 ppt. A salt chlorinator by comparison usually operates on only 0.4-0.7% (4-7ppt) salt.

It is impossible to guess an accurate salt level and while some chlorinators test for salt they can only approximate. The best way to test your salt is to take a water sample to any poolshop, or you can even buy test strips now!! We recommend all salt chlorinators operate at between 0.6%-0.7% salt. This will also help extend the cell life.

Salt levels can be increased by the use of liquid chlorine which is sodium hypochlorite, i.e. contains salt, however it is only a small amount, unless used for extended periods.

See: Salt ChlorinatorsProducts

This PDF factsheet contains seasonal maintenance information for owners of salt chlorinators on concrete pools.

Pool Care Guide for Salt Water Pools [PDF]

Stabiliser (isocyanuric acid)

Stabiliser (isocyanuric acid) is a very misunderstood product. The purpose of stabiliser, formerly known as sunscreen is to hold chlorine in the water so it cannot be removed as easily by UV light.

There is extensive debate over the correct amount of stabiliser to use. The Health Dept. recommends between 30ppm-100ppm. In the US however this maximum is increased to 200ppm. In pools using normal unstabilised chlorine or with chlorinators a level of 80ppm-120ppm will ensure chlorine is not wasted. These maximums are arbitrary levels as no definitive maximum is known.

The only way to lose or lower your stabiliser level is to remove water.

Many people have heard of ‘chlorine lock’, a situation where there is too much stabiliser so your chlorine won’t work. This can occur in pools using stabilised chlorine (e.g. floating tablets, dichloroisocyanurate dihydrate or trichloroisocyanuric acid). When dichlor or trichlor are added to a pool they split to produce free chlorine and stabiliser. These can be useful when dosing a pool to remove algae or boosting a chlorinated pool with chlorine. If the level of stabiliser is too high when adding stabilised chlorine an incomplete reaction may occur not allowing enough free chlorine into the water. The simplest action to take is to dose your pool with more unstabilised chlorine. This will help break the reactions and free the chlorine into solution. This is why we do not recommend the continuous use of stabilised chlorine in swimming pools. It is cheaper to add stabiliser separately and use regular chlorine.

Most dichlor and trichlor products recommend on their packaging only to use them if the stabiliser level is below 50mg/L. If the level is above this you should use unstabilised chlorine. The only effective way to lower stabiliser levels is to remove water (dilution). If your level is a concern I recommend using only unstabilised chlorine products for the next 6 months and then reassessing the level.

If you are using excessive amounts of chlorine or the pool is getting green algae even with the correct chlorine dosage, especially during summer months, you should check the stabiliser level at your local poolshop. Test kits for stabiliser are available but it is not included in a standard test kit. 3kg of stabiliser at the beginning of summer each year should be sufficient for a 55,000L pool (standard size).

MSDS Data Sheets

It is a requirement of Workcover Australia that under our Occupational Health & Safety laws all chemicals used or handled in an organisation should have available MSDS data sheets identifying the chemical, it’s components and it’s health risks as well as appropriate action to take in the case of an emergency or spill.

MSDS data sheets can be found for all swimming pool chemicals. These are available from the MSDS website.



All algaecides are not created equal. Choosing the right algaecide for the problem will make looking after your pool significantly easier. If you have algae and are trying to kill it a product like LoChlor Starver which removes phosphates from the water and ‘starves’ the algae is suitable. Especially if the algae has a luminous green nature. Always try shocking the algae with chlorine first. Most algaecides contain copper sulfate as the active ingredient. These algaecides are good for preventing algae. Winterisers have higher concentrations up to 40gm/L whereas the summer or standard algaecides are much weaker. If you have an ioniser in your pool you will already have a copper level so do not use these algaecides. For cases of black or brown algae a stronger algaecide made on a quaternary ammonium base like LoChlor Tropiclear can help kill and prevent the algae from growing.

If you get black staining, frothing water (bubbles) or cloudiness after adding an algaecide then do not add any more for a while. A high copper level can be caused by excessive use of algaecides. Algaecide is based on detergent and too much can cause a froth. In some cases a pool may go cloudy when the chlorinator operates after adding algaecide. This is due to a chemical reaction due to excess detergent. Again, do not add algaecide and it will go away. Add acid to remove staining. You can add water to the pool (and drain some out) to fix this faster.

Most algaecides last for up to 3 months. The most important times for algaecides are in winter when the pool is not being used or looked after as much and in summer when the pool is being heavily used and the sun is making conditions right for growth.

Always check that you are dealing with algae and not a stain. Algae should move when brushed or feel slimy to the touch and you might be able to wipe it off with your hand. A stain will not be recognisable to feel and it will not brush off.

The Langelier Index

The Langelier Scale, later to become the Langelier Saturation Index (LSI) , was originally developed by Dr Wilfred Langelier. It is a very accurate way of determining water balance and is often used by builders and poolshops.

The LSI is mathematical calculation that takes into account four factors: pH, Alkalinity, Calcium Hardness and Temperature. A minus figure is under-saturated and corrosive while a positive figure is over-saturated and has a tendency for scaling to occur. The accepted limits are -0.5 to 0.5 . Perfectly balanced water has an LSI of 0.

The LSI can be interpreted as the pH change required to balance the water.

A positive LSI means you should lower your pH (add acid).
A negative LSI means you should increase your pH (add soda ash or buffer, depending on alkalinity).
NOTE: Buffer primarily increases alkalinity and as a side effect increases pH, while Soda Ash will only increase your pH.

We only adjust these variables because you cannot adjust temperature and calcium hardness easily.

To make it easy for you to calculate the LSI for your pool we have provided a FREE program that will do it for you. By adjusting the various levels you can test and then correct your balance. Try adjusting your figures and see what works best.

See our software

Sydney Water Restrictions

For those living in the Sydney, Illawarra and Blue Mountains areas, mandatory water restriction have been in place since October 2003. The latest information on water restrictions is available from Sydney Water [link below].

Level 3 restrictions (June 1, 2005) do not affect the topping up of pools but do affect the filling of new or renovated pools.  You must apply for a permit to fill a new or renovated pool over 10,000 litres. You must apply for a permit to fill a new or renovated pool. A renovated pool is one which has had substantial changes to it’s shape or major additions to the structure. To obtain a permit you will need to install indoor water efficient appliances, which are available from Sydney Water.

You ARE allowed to leave a hose unattended filling a pool or spa.  You may also hose hard surfaced areas briefly if any chemical has been spilt, if brooms or other waterless alternatives cannot clean up the spill.

You ARE allowed to fill a pool or spa, as long as waterwise procedures are adopted.  The amount of evaporation in your pool does not change with the depth of the water.  As a result we recommend customers allow their pools to fill with rainwater or to fill them with a hose to a higher level.  This means it will be a lot longer before you have to add water to your pool again and it also means there is less chance of damage to your equipment from lack of water.

Fix any leaks in your pool or spa.  If you are losing more than 1″ of water a week you may have a leak.  Check the backwash line (to the drain) and the equipment for leaks when the system is operating.

Spas must be emptied every 4 months for health requirements.  There is no way to avoid this without the water becoming unhealthy.  Use the water to water your lawns and gardens.  Properly sanitised pool or spa water is healthier than tap water.

Backwash only when necessary and if possible run the water onto a lawn or garden.  Properly sanitised pool or spa water is healthier than tap water.

Cartridge or D/E filter elements should be cleaned on a grass area witha hose that has an on/off trigger nozzle or similiar and, if possible, with a device that limits the flow of water to 10 litres or less per minute [required for exempt businesses].

Cartridge filters use less water than a sand or diatomaceous earth filter.  To hose a cartridge using a pressure cleaner or jet nozzle should only require up to 15 litres of water.  Backwashing a filter can use up to 350 litres per minute.

Solar Covers can help reduce the amount of evaporation from a pool however they may not suit all pools. A suction cleaner will not operate properly underneath a solar cover and solar covers will still allow leaves to sink into the pool. See Information section for more on solar covers.

See: Sydney Water