Learning and understanding how your pool works will help you to achieve water that not only looks inviting but is also clean and safe to enjoy. Swimming pool maintenance can be a little baffling and so the BOAST pool chemical system was created with the intent of simplifying all that chemical jargon and complicated formulae, making it possible for everyday swimming pool owners to run their swimming pools economically and successfully.
What does BOAST stand for?
B : Balance of your swimming pool water for maximum chemical efficiency
O : Oxidise to establish a sanitiser level, then again weekly to destroy all unwanted waste products
A : Algae prevention
S : Sanitise to prevent and destroy bacteria
T : Test your water on a regular basis
Balancing your pool water
Keeping well balanced pool water is important for a number of reasons including:
- Chemical efficiency
- Swimmer comfort
- Ensure the protection and longevity of pool and plant room equipment
- Water quality and appearance
To achieve the correct water balance, the pH of the water, Calcium hardness, Total Alkalinity and Total dissolved solids must all be maintained within their ideal levels. These are as follows:
Calcium Hardness: 200-275mg/l
Total Alkalinity: 80-150mg/l
Total Dissolved Solids: less than 1,500mg/l
The pH is a measure of how acidic or alkaline the water is. The pH scale ranges from 0 to 14 with 0 being most acidic and 14 being very alkaline. The ideal pH for swimming pool water is between 7.2 and 7.6. This results in the water being slightly alkaline which protects the pool and plant room equipment from the water becoming too aggressive and corrosive. If the pH of your swimming pool is left to rise above or below this desired figure the following problems can occur:
PH drops below 7.2:
- Water becomes corrosive
- Etching of surfaces
- Irritation to the skin and eyes
- Damage to swimming pool components and equipment
PH rises above 7.6:
- Scale Formation
- Filter calcification
- Cloudy water
- Drying of skin
- Reduced effectiveness of chlorine
If the pH of your pool water is allowed to rise above or below these figures, it should be corrected with pH plus and minus.
What is calcium hardness?
Calcium Hardness, also often referred to as total hardness is the measure of how hard or soft the water is. This varies depending on where you live and where your water source comes from. The hardness of your water depends upon the amount of mineral salts that are dissolved in the water, with more salts creating harder water. If the calcium hardness of your pools water is left to drop below 200mg/l then it is considered to be corrosive resulting in etching of surfaces, staining of the swimming pool shell and foaming of the water. On the other hand, if the calcium hardness is left to raise above 275mg/l then scale formation will occur, accompanied by filter calcification, lower effectiveness of sanitizers which will result in cloudy water. If the calcium hardness does alter from the desired levels, calcium hardness raises and stain and scale inhibitors can be added to the pool water to return it to normal.
Total Alkalinity is the measurement of the waters ability to resist changes in the pH. If the total alkalinity is low then pH can fluctuate making it difficult to control and maintain a desired level. A raised level of total alkalinity can result in bicarbonate scale on pool surfaces, within pipe work and in all plant room equipment. Total Alkalinity raisers and reducers can be added to your swimming pool water to bring it back to a desirable level.
Total Dissolved Solids
The total dissolved solids are the sum of everything that is dissolved in the water. This includes all minerals, chemicals and debris. The maximum recommended figure for total dissolved solids is 1,500mg/l. Elevated levels of total dissolved solids can cause poor chemical efficiency and increase consumption accompanied with dull looking, salty water. To bring elevated levels of total dissolved solids down, you can dilute the water by removing some of the old pool water and adding some fresh water accompanied by regular backwashing.
One of the major reasons for chlorine loss from a swimming pool is due to chlorine being drawn out of the water by UV rays from the sun. With the addition of chlorine stabilisers to any outdoor pool in the summer, the amount of chlorine lost to sunlight will be significantly reduced. The ideal chlorine stabiliser level is 60mg/l, and if it is left to drop below this figure, then tablets or granules will need to be added to increase it. If the chlorine stabiliser level is left to increase above 200mg/l, then you will need to drain some of the pool water and then top it up again with fresh water to bring the level down.
Oxidise your swimming pool
Waste products can find their way into your swimming pool in a variety of ways but most commonly through rain water and swimmers. All of these waste products will eventually build up and become a feeding source for bacteria and pathogens, making your pool water take on a cloudy appearance and most importantly turn unhealthy. Chlorine will in turn react with these organic wastes to produce chloramines that can be irritating to the eyes and respiratory system and produce a foul odour. By oxidising and shocking your swimming pool, you rid the water of these unwanted chloramines and wastes and make the pool water safe and more pleasant for bathers once again.
Chlorine demand is the amount of chlorine that is required to destroy bacteria, algae and other unwanted organic waste products. The only way to overcome chlorine demand is to keep shocking the pool until the chlorine dissipates. It is a straight forward procedure but may need to be carried out over a few days depending on the level of demand. To carry this out, keep shocking the pool until the chlorine remains above 5mg/l. If it remains at this level for the following few days, the pools craving for chlorine has been satisfied. Regular oxidising of your swimming pool will pay you back in the long term in the prevention of pool water problems.
Algae are microscopic plant life that given the right conditions, will multiply rapidly turning your pool water an unpleasant green colour. Trying to recover an algae infested pool can be very time consuming and expensive, so algae prevention is the key here. To keep your swimming pool algae free, the BOAST system comes into play. By maintaining the correct water balance, oxidise regularly to destroy any food source for the algae to flourish, apply algaecide to support the sanitiser, keep a consistent sanitiser level and test your water on a regular basis to ensure all is being maintained at desirable levels, you will be rewarded with an algae free pool.
There are now many products on the market which can control and eliminate algae infestations being applied weekly, monthly and even bi-annularly.
Sanitise your pool water
Sanitisers or disinfectants in the form of chlorine or bromine added to your pool will keep the water healthy by preventing and killing bacteria.
Chlorine is the most commonly used chemical in swimming pools to achieve satisfactory bacteriological and chemical purity in swimming pools. It must be present in its free form to kill bacteria and pathogens and to oxidise organic matter. If your water is correctly balanced, chlorine levels should be kept between 1.0 and 3.0mg/l to maintain clean and healthy water. Chloramine levels should be of less than 0.5mg/l if your pool is being correctly treated.
The most common way of adding chlorine to your pool is in the form of granules but tablets and chlorine dispensers are also available on the market and the best option should be chosen for your swimming pool individually.
Bromine is similar to chlorine in how effective it is as a sanitiser but does have some very distinct differences:
Pools that are sanitised with bromine do not require the addition of a chlorine stabiliser as bromine is not lost to sunlight in the way that chlorine is.
Bromine should be added to the pool via a chemical feeder which is usually installed in the plant room
Bromine combines with organic compounds in the same way that chlorine does but unlike the chloramines that are produced with chlorine, bromamines produce no smell with less risk of irritation to the skin, eyes and respiratory system.
Bromine retains better levels of efficiency over a wider pH band than chlorine.
Bromine levels need to be kept between 3.0 to 5mg/l, 2.2mg/l of bromine is needed to equal 1mg/l of chlorine.
Test your pool water
Testing your pool’s water has been considered the first discipline of pool water management but the BOAST system is a circle that leads onto balancing, oxidising, algae prevention and sanitising.
There are four methods of testing your swimming pool water which consists of testing strips, pool testers, comparator test kits and electronic test kits. Whichever testing method you choose to use for your swimming pool, it is important that you test on a regular basis, every 2-3 days will suffice, with daily testing when the pool is being used on a more regular basis.
As previously mentioned, calcium hardness, total alkalinity, total dissolved solids and chlorine stabilisers also need to be tested and there are test kits available to test all of these yourself. Another alternative is to take a water sample to your local swimming pool company and they should be able to carry out these tests for you.
As outlined in this article, swimming pool maintenance works in a circular formation with each area having a knock-on effect on the next. Ensuring all areas are well maintained, you will be left with an inviting and safe pool to enjoy at your leisure.