Frequently Asked Questions
Here at swimmingpoolsupplies.co.uk we pride ourselves on the unbiased advice that we offer, here are some of the frequently asked questions we receive, if there is a question we haven't answered here either call us on 01924 479717 or send us an email from our Contact Us page.
Water Chemicalisation
Often I need to add more than one chemical to the pool water at the same time, can I mix them all in one bucket and throw them in the pool together?
NO. CHEMICALS MUST NEVER BY MIXED. This might cause chemical reactions, such as explosions, fire, or the release of toxic chemical compounds. These could injure yourselves or anyone else in the pool or pool hall or even damage to the pool. Always read and follow the instructions on chemical containers.
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What is pH?
"pH" refers to the acidity/basicity level of your pool water. The pH is important because your pool water sanitisers won’t be able to function correctly and keep the water safe for swimming. It is quite easy to measure the pH using pool testing kits / strips. If the pH of the pool is too high add pH minus, (as recommended by the manufacturer), if the pH is too low, add pH plus (again as per manufacturer’s instructions).
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Why does my pH keep falling?
You need to test the Total Alkalinity. Total Alkalinity helps maintain the pH stable and in the proper range. The ideal range for Total Alkalinity depends on the type of sanitiser used. Keep the total alkalinity between 100 – 120 ppm is you use trichlor, sodium dichlor or bromine tablets. Keep the range between 80 – 100 ppm, if your sanitiser is calcium hypochlorite, or sodium hypochlorite. When using Baquacil or Revacil sanitisers maintain the range of total alkalinity between 80 – 120 ppm.
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What is water balancing?
It is important to maintain the correct level of calcium hardness and total alkalinity, this is water balancing. If either of these levels is incorrect there is a possibility of damage to equipment, including covers and liners and may invalidate manufacturer’s guarantees. The levels of both calcium hardness and total alkalinity are easily tested for and adjusted using products which we always keep in stock.
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Why do I need to shock my pool?
When sweat, urine and other organics enter the pool water, they react with the chlorine to produce Combined Available Chlorine, also known as chloramines. This Combined Available Chlorine is not as effective as Free Available Chlorine at removing the organic matter. Also it doesn’t smell nice and is an eye and skin irritant. Shock dosing your pool will free up the Combined Available Chlorine and return it back to the water as Free Available Chlorine.
You can shock the pool with either a chlorine-based or non-chlorine shock product. However, if the pool has low or no chlorine or if it has algae, it must be shocked with a shock product containing chlorine.
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How long should I wait after shocking my pool to be able to swim?
This depends on what you are using to shock your pool. If you are shocking with a chlorine product it is recommended that you wait and stay out of the pool until the chlorine level drops to 2.0-4.0 ppm. In some pools it could be up to 8 hours or 36 hour. It all depends on the chlorine demand of the pool itself. You will need to re-test the pool water as this is the only way to know if it is at this safe level to re-enter the pool. If you are shocking the pool with a non-chlorine shock treatment, swimmers may re-enter the water as soon as 15 minutes after shocking the pool.
What is super-chlorinating, and how often should it be done?
Super-chlorinating is just what it sounds like: Instead of putting in 2 ½ ounces of chlorine per 10,000 gallons, you put in 5-10 times that amount.
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What is Free Residual Chlorine?
Free Residual Chlorine is the amount of available chlorine in your pool water.
What is the difference between stabilised chlorine and shock chlorine?
Shock chlorine and calcium hypochlorite lose their effectiveness after 4 hours. Stabilised chlorine has a built-in-stabiliser which protects the chlorine from the sun’s rays and will keep working for over 24 hours, resulting in more chlorine being in the water to do the job of sanitising.
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Why does my pool use up chlorine as quickly as I add it?
Assuming that your pool is an outdoor pool and the correct amount of cyanuric acid (conditioner or stabiliser) has been added to the pool, there are many variables to look at (this is by no means a comprehensive list):
What kind of chlorine are you using and how are you adding it to the pool? If you are hand-feeding granular chlorine, the chlorine can be used up very quickly when people use the pool since there is no additional chlorine being added to the water. If you are using an automatic chlorinator, the chlorine output is based upon the amount of time the circulation system is operated and the amount of tablets in the unit. If the circulation system is not being run long enough, not enough chlorine is getting into the water. If you are using a floating chlorinator, the water temperature and the number of tablets determine how much chlorine is getting into the water.
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My chlorine level is very high, what can I do?
You need to use a de-chlorinating agent. Simply follow the label directions.
Why do swimmers get sore eyes and a chlorine smell when my test says the chlorine level is about right at 1.5ppm?
Strangely this is because there is probably not enough chlorine in the water. Usually the chlorine in the water will break up organic material, but if the chlorine level is low or the organic material level is high the chlorine slows down its work rate. The result being the production of Nitrogen Trichloride instead, thisi is a type of tear gas, hence the sore eyes. The swimmers smell the Nitrogen Trichoride which is easily mistaken for chlorine. It is best if you can try to anticipate a raise in bathing load and therefore in organic material level.
Stinging eyes could also be caused by the pH of your pool being too high, so always check this.
I'm having a pool party later and a lot of people will be swimming, should I do anything now?
You can prepare for the high usage of your pool by raising the chlorine level to 4-5ppm. This will make sure that any organic matter which ends up in the pool as a result of the increased bathing load can be dealt with immediately by the chlorine and hopefully should prevent any problems after the party.
Is it best to use granular chlorine or Trichlor tablets?
It is likely that you should used both, both forms of chlorine do the same job, but in different ways.
Tablets maintain the chlorine level all the while you have the filter running and are easier to use. The chlorine level is easier to control using chlorine granules if you know the volume of your pool. Most pool owners use chlorine tablets to maintain the underlying chlorine levels and use chlorine granules to make adjustments to the chlorine level. These adjustments could be in anticipation of or after increased pool usage, during very sunny weather.
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Why does my test read zero when I have added chlorine?
If you repeat the test and the tablet stays white and the water is clear when the tablet has dissolved then the chlorine in the swimming pool has been used up, maybe there was a heavy bathing load or very sunny weather. It is also possible that you have so much chlorine in there that you have bleached out the reagent that does the testing. One way to test this is to dilute a sample of pool water by a known dilution factor, (one ml pool water in 10mls tap water) and multiplying the result by the dilution rate (in this case 10).
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What is TDS?
Total Dissolved Solids (TDS) is the sum total of all the dissolved material in the water. TDS can arise from disinfectants, balance chemicals, Calcium Hardness, source water, bather waste, algaecides, Total Alkalinity, windblown dust and dirt, phosphates, nitrates, and sulfates. It is not possible to prevent the buildup of TDS as every time you add chemicals to the water, the TDS increases. Even topping up the pool increases TDS. This is because only pure water evaporates, this leaves all material that was dissolved in the water remains behind. This builds up over time, increasing the TDS.
The ideal range of TDS is from 1000 ppm to 2000 ppm, and the maximum level is 2500 ppm to 3000 ppm. The only way to reduce TDS is to drain or partially drain the pool and replace the water.
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