Cloudy Swimming Pools

By swimmingpoolchemicals.co.uk

Cloudy water is one of the most common problems pool owners face. There are three main causes of cloudy water.

  1. No chlorine or bromine
  2. Filter not functioning properly
  3. Dissolved air

In this blog post we will advise you on how to restore the sparkling look to your water.

The first thing to do is check your chemical levels and in particular the chlorine, pH, alkalinity and stabiliser (cyanuric acid).

If the chlorine or level is low, shock the pool with 500 grams of chlorine shock per 10,000 gallons of pool water. (For a very cloudy pool it may be necessary to use double this amount or more.) Leave the water to circulate overnight and re-check the chlorine level to ensure it is at least 5 ppm. If the stabiliser level is very high on the test strip then you will need to replace a portion of your water with fresh water to bring it down. For all the other parameters make sure they are within the required limits as stated in the table below.

Pool Spa
Chlorine 1-3ppm 2-4ppm
Bromine 3-6ppm
pH 7.2-7.6 7.2-7.6 (7.2-8.2 if you are using Bromine)
Alkalinity 80-120 80-120

If all your parameters are within range then the cause of the cloudy water is probably down to fine particles of debris or material passing through the filtration system. When the water passes through the filtration system the role of the sand, EGFM or cartridge is to trap any debris or material and prevent it from returning into the pool. Sometimes these particles are so fine that they pass straight through the filter and re-enter the water. These fine particles are the cause of the cloudy water.  This is particularly common when you have had to shock your pool to kill a lot of algae or if you have had a lot of people using your spa.

In order to eliminate these particles and restore water clarity a flocculant needs to be added to the water. The flocculant (also known as a coagulant) enhances the removal of the fine particles by clumping them together so they form a flocculus (floc) which is more easily trapped in the filter.

If after checking your chemical levels and adding a flocculant you still have cloudy water, then you need to check your filtration system is working properly. If you have an above ground pool or spa then remove the filter cartridge and give it a thorough clean. If you have an in-ground pool you will need to check that your pump is working. You can do this by seeing if there is water coming back into the pool via the inlet. If the pump appears to be working then back wash the filter and then remove the lid to check the level of the sand. When checking the level of the sand always use a tape measure as when the filter is full of water it looks as though the sand is closer to the top than it is. Your filter should be two thirds full of sand. Whilst doing this also observe the state of the sand. It should be clean, reasonably level and should have no gaps or holes in it. If the sand level is not as described above, the filter should be emptied and the distributor at the bottom should be checked and repaired if necessary. Finally new sand or EGFM needs to be added to the filter.

The last and least common cause of cloudy water is dissolved air. This is caused by a leak on the suction side of the pump where air is sucked in and dissolved in the water when it passes through the pump. When the water gets back to the pool it forms very small bubbles which are suspended in the water making the pool look cloudy. Pools with dissolved air also tend to foam when the water is disturbed. The most common place for a leak to occur is the lid of the strainer. To check for this turn off the pool pump and close the valves. Remove the strainer lid and examine the seal. Wipe the seal and put some vaseline on the seal before putting the lid back.

The other common place for air to get in is the mechanical seal. Check under the pump for evidence of water leaking. If it is leaking you will either have get a replacement mechanical seal or a new pump.

If the strainer and pump are OK check all the pipework from the pool to the pump for leaks on joints or cracks in pipes.

Opening your pool for the Summer?

By swimmingpoolchemicals.co.uk

Winter is firmly behind us and pool owners across the country are pulling back the pool cover and getting the pool ready for the summer. If you winterised the pool at the beginning of last winter then opening the pool should be a relatively straightforward process, but nevertheless here is a simple step-by-step guide on how to get your pool ready.

Preparing the Pool

  1. Remove any leaves and debris from the winter cover. Take the winter cover off, clean it and store it away.
  2. Connect the pool pump and filter and reconnect all hoses and electrical connections.
  3. Remove leaves and debris from skimmers, filters, pumps and drains.
  4. Remove any debris and leaves that are in the pool using a leaf skimmer.
  5. Fill the water up to the proper water level. The water should be halfway up the skimmer opening.
  6. Turn on the filter pump and make sure all skimmers, bottom drains and filters are functioning properly.

Adjusting the pH and Alkalinity Levels

  1. After the pool filter has been running for 3-4 hours, test the pH and alkalinity levels and compare with the table below.
  2. To reduce the pH level use pH Reducer. Dissolve a small amount (450g per 10,000 gallons) in a bucket of pool water and distribute it around the pool with the filter operating. Retest after 4 hours.
  3. To increase the pH level first adjust the Alkalinity to between 60-100ppm. To increase the Alkalinity level by 12ppm add 1kg Alkalinity Builder per 10,000 gallons directly to the pool with the filter operating. Retest the Alkalinity level and the pH level after 4 hours.
  4. If the pH level is still too low dissolve a small amount (450g per 10,000 gallons) of pH Increaser in a bucket of pool water and distribute it around the pool with the filter operating. Retest after 4 hours. Repeat this dosage if necessary.
Low OK Ideal OK High
pH Less than 7.0 7.0-7.2 7.2-7.6 7.6-7.8 Over 7.8
Total Alkalinity Less than 40ppm 40-60ppm 60-100ppm 100-120ppm Over 120ppm

Shock Treat the Pool

  1. Brush the pool walls and steps and vacuum up any debris. This will expose the algae to the chlorine.
  2. Dissolve 500 grams per 10,000 gallons of Chlorine Shock in a bucket of pool water and distribute around the pool. DO NOT ADD TO THE SKIMMER BASKET IF IT HAS HAD STABILISED CHLORINE IN IT AS IT MAY EXPLODE IF MIXED!!!
  3. Depending on how green the pool is it might require several shock treatments. If your pool is very green you can double the initial shock dose. Following the shock dose, backwash the filter to remove any debris.

Stabilising the Chlorine Level

  1. After a few days your chlorine level should have returned to normal (see table). Once it has you can now add a 200g Multifunctional tablet or 200g Stabilised Chlorine tablet to your skimmer basket or dispenser.
  2. To improve the clarity of the water add Sparkle Water Clarifier to a bucket of pool water and distribute around the pool.
  3. To prevent algae re-occurring add Polyquat Algaecide to a bucket of pool water and distribute around the pool.
Low OK Ideal OK High
Chlorine Less than 0.5ppm 0.5-1.0ppm 1.0-3.0ppm 3.0-5.0ppm Over 5.0ppm

Daily Maintenance

  • Monitor Chlorine, pH and Alkalinity levels using AquaChek Free Chlorine Test Strips.

Weekly Maintenance

  • Clean the skimmer baskets and brush the walls, steps and bottom of the pool. Vacuum if necessary.
  • Clean the strainer basket before the pump. When this is complete backwash the filter.
  • Shock dose the pool. Dissolve the required amount (see instructions) of Chlorine Shock in a bucket of pool water and distribute around the pool. DO NOT ADD TO THE SKIMMER BASKET IF IT HAS HAD STABILISED CHLORINE IN IT AS IT MAY EXPLODE IF MIXED!!!
  • Add Sparkle Water Clarifier to a bucket of pool water and distribute around the pool.
  • Add Polyquat Algaecide to a bucket of pool water and distribute around the pool.

Dosing Information – Health and Safety

  • Always wash out the container you mix chemicals in thoroughly with pool water before and after use.
  • Do not ever mix chemicals together
  • Always add chemicals to water not water to chemicals.

What is Bromine?

By swimmingpoolchemicals.co.uk

What is bromine?

Bromine is the most widely used sanitiser for domestic hot tubs and spas. Bromine destroys bacteria, algae, and water-born diseases in much the same way that chlorine sanitises water.

What is the difference between bromine and chlorine?

• Bromine does not form the corrosive by products which cause corrosion of metals in indoor pools

  • Bromine is less volatile than chlorine so it does not evaporate as quickly at the high temperatures which spas operate.
  • Bromine does not form smelly by products, so indoor pools using bromine do not have that typical swimming pool smell. When you have used a bromine hot tub your skin will not smell of chlorine.
  • Bromine does not form the corrosive by products which cause corrosion of metals (including stainless steel) in indoor pools.
  • Bromine does not lose its ability to kill bacteria and viruses at pH values up to 8.2. This is useful on hot tubs in hard water areas where it is difficult to keep the pH down.
  • Bromine cannot be stabilised against breakdown by sunlight, so it is not often used in outdoor pools.
  • Bromine is two and a quarter times as heavy a molecule as chlorine so it is used at a concentration 2.25 times as high as chlorine.

How is bromine dosed?

  • Bromine is normally supplied as white tablets, bromo-chloro-dimethyl hydantoin (BCDMH).
  • In hot tubs these are usually placed in a floating dispenser. The dispenser is adjusted to give a bromine level between 3 and 6 ppm.
  • Bromine tablets are very slow dissolving making them very useful in domestic hot tubs. On a hot tub that is used by two people twice a week two tablets in the floating dispenser will keep the water clear and fresh. One extra tablet will need to be added every 7 to 10 days.
  • Indoor swimming pools usually use an erosion feeder known as a brominator to dose bromine tablets. Because bromine is so slow dissolving it is essential that brominators on busy pools and spas are large enough to meet the bather load.

How much bromine should be kept in bathing water?

  • Spas and hot tubs 3 to 6ppm
  • Swimming pools 2 to 4 ppm

How do we test bromine?

  • Bromine is tested using exactly the same test as chlorine using DPD 1 tablets.
  • This is read against color standards in a visual comparator.
  • Since Free Bromine and Combined Bromine are similar in sanitising strength, they both react with a DPD 1 tablet. This reading represents the level of Total Bromine.
  • If a bromine comparator is not available, operators can use a chlorine comparator and multiply the reading by 2.25 to calculate ppm bromine.
  • Bromine can also be tested using bromine test strips.

What pH should a bromine bathing water use?

As mentioned before bromine does not lose its ability to kill micro organisms as pH rises. This means that hot tubs and pools using bromine can use a pH up to 8.2. This is particularly useful on hot tubs and leisure pools where the pH tends to rise if an adequate alkalinity level is maintained.

The Chemistry (if you are interested)

Bromine and ammonia

In common with free chlorine, free bromine also reacts with the ammonia (NH3) which is continually added to the water through the decomposition of the urea in the nitrogenous products (urine, sweat etc.) introduced by bathers.  However, there are significant differences between the two sets of reactions.

The first bromine reaction is:

HOBr (hypobromous acid)NH3 (ammonia)NH2Br (monobromamine) H2O (water)

This reaction is normal and acceptable. Monobromamine is not an irritating compound and has disinfecting properties as powerful as free chlorine or free bromine. Consequently, when the pollution level increases the product of its reaction with the free bromine is still effective against micro organisms.

The second reaction, analogous to the production of dichloramine, is:

HOBr (hypobromous acid)NH2Br (monobromamine) <> NHBr2 (dibromamine) + H2O (water)

It should be noticed that this is an equilibrium reaction with the equilibrium strongly to the left. It is not possible to drive the equilibrium to the right under pool conditions, therefore the concentration of dibromamine is minimal. This is analogous to the breakpoint condition in a chlorine pool.

Brominous disinfection is, therefore, effectively always at breakpoint. The absence of dibromamine ensures that nitrogen tribromide – the bromine equivalent of the atmospheric irritant nitrogen trichloride – cannot form. Consequently the irritating conditions for bathers and the corrosive conditions for bathers cannot occur in an indoor bromine pool.

Chlorine or Bromine in a Hot Tub?

By swimmingpoolchemicals.co.uk

One of the most common questions we get asked from spa and hot tub owners is which is the best sanitiser to use – Chlorine or Bromine? There are many theories out there as to which is better, however we decided to gain firsthand experience and run our test hot tub on both in order to provide you with a practical answer. The conclusion we came to is that both are perfectly suitable sanitisers, however bromine does boast three crucial advantages over chlorine, which we believe makes it a more suitable sanitiser for hot tubs.

Less odorous – Running your spa on chlorine can create a strong chlorine smell in the water even when the chlorine level is kept within the recommended range of 2-4 ppm. Although this is perfectly normal it can result in an unpleasant bathing experience. Bromine is less odorous than chlorine and as a result this smell doesn’t exist and a more pleasant bathing environment can be enjoyed.

Effective at a broader pH range – The recommended pH level for a chlorine spa is 7.2 – 7.6. This is because the effectiveness of the chlorine as a sanitiser significantly decreases at higher pH levels. Bromine on the other hand, is an active santiser at pH levels of 8.2, therefore the pH level can be maintained at a much broader range of 7.2-8.2. This allows more flexibility when controlling the pH level and is particularly beneficial for hard water areas where the incoming water supply naturally contains high pH and alkalinity levels.

Slower dissolving – Regardless of which sanitiser you use, both are available in tablet form and ideally should be used in conjunction with a floating dispenser. The main difference we experienced is that bromine is much slower dissolving than chlorine and as a result it is a lot easier to maintain the correct sanitiser level in the water. This is crucial in order to reduce the amount of work involved in maintaining your hot tub.

To make this a fair argument it is only right that we look into the disadvantages of using bromine over chlorine. As bromine is slow dissolving it can have difficulty in recovering an adequate concentration after the hot tub has been heavily used or is started up after being emptied. In this case you need to add another sanitiser such as oxy shock or stabilised chlorine granules just to boost the level. Another disadvantage is price, as bromine is a little more expensive than chlorine.

Despite these drawbacks we firmly believe that the advantages of using bromine over chlorine far outweigh the disadvantages. As a result we would always recommend using bromine as opposed to chlorine in a hot tub.

Summer’s coming to an end – what to do next?

With the school holidays over and autumn on the horizon, many pool owners will start thinking about closing their pools. The good news is summer doesn’t appear to be going without a fight as forecasters are predicting prolonged spells of warm weather for some parts of the UK over the next couple of weeks. Therefore you may want to put any plans to close your pool on hold for a bit longer….

When you decide that the time has come to close your pool for the winter then this blog post is designed to give you a helping hand. If you have an in-ground pool then it is strongly advised that you winterise your pool. If you have an above ground pool then you can also winterise your pool or you have the additional option of emptying it and storing it away for the winter if that is easier.

The winterising procedure is very important for two reasons. Firstly it helps ensure your pool is in the best condition possible when you come to open it up again in the spring and secondly it helps protect your pool and its fittings from the winter conditions. To winterise your pool simply follow this step-by-step guide;

  1. Backwash the filter and clean the strainer.
  2. Check the pH is between 7.2 and 7.6 and use sodium bisulphate (to lower pH) and sodium carbonate (to increase the pH) to adjust if necessary.
  3. Using Chlorine Shock (calcium hypochlorite), boost the chlorine level to remove any algae that maybe present in the pool. The recommended dosing rate is 1kg per 10,000 gallons of pool water.
  4. To prevent algae from growing add Winterising Algaecide. The recommended dosing rate is 2.5 litres per 10,000 gallons of pool water.
  5. Turn on the circulation to disperse the solution through the water for a period of 24 hours.
  6. Reduce the water level to just below the skimmers. This is to allow for any extra water that enters the pool, ie rainfall, therefore preventing it from overflowing. WARNING: Do not lower the level too much especially if the water table is high as this could cause structural damage to the pool shell.
  7. To protect any exposed metal surfaces, drain the water from the pump(s), filter(s), heater and pipework.
  8. Leave any valves above the water level open. Any below should be closed to protect from frost damage.
  9. Switch off the electricity supply to the system.
  10. Cover the pool with a heavy-duty winter pool cover.
  11. Check the appearance of the water, and the chlorine/pH levels occasionally during the winter.

By following this set of guidelines it should significantly reduce the amount of work you have to do when opening the pool up in the spring. Winterising Kits are available from our website which include all the chemicals you need as well as step-by-step instructions.

Please note the information provided on this page is believed to be correct but is given without warranty and no liability is accepted or implied. Please use this information in conjunction with manufacturers instructions.

 

Chlorine explained

By swimmingpoolchemicals.co.uk

The most important chemical when maintaining a swimming pool is chlorine. Maintaining the correct level of chlorine in pool water will kill almost all bacteria and viruses introduced into the water by bathers within a few seconds. As a result, the water will remain clear and safe to swim in.

Chlorine is the most commonly used sanitiser in swimming pools and it comes in many forms. The most common types used in pools are:

Liquid Chlorine – Sodium Hypochlorite

Trade Name Chemical Name Strength (Available Chlorine %)
Stabilised Chlorine Granules or “Dichlor” Sodium Dichloro-iso-cyanurate 56%
Stabilised Chlorine Tablets or “Tritabs” Trichioroiso cyanuric acid 90%
Shock Chlorine Granules or “Shock” Calcium Hypochlorite 65 – 70%
Unstabilised Chlorine Tablets Calcium Hypochlorite 65 – 70%
Liquid Chlorine or “Liquid Shock” Sodium Hypochlorite 11 – 15%

Chlorine is also generated electrolytically from salt water. The type of chlorine you buy makes very little difference. The key point which people do not always appreciate is that once the chlorine is dissolved in water it is all the same. Any form of chlorine, when added to water produces hypochlorous acid (HOCl) and it is the hypochlorous acid that kills bacteria, viruses algae in the pool water. This can be referred to as ‘Free Chlorine’.

Contaminants in the water can use up the free chlorine.

Free chlorine is used up by:

  • Pollution from sweat and all the other dirt that washes off bathers – this forms chloramines which cause irritation to bathers and the classic chlorine smell onindoor pools.
  • Contaminants getting into the pool such as leaves, dust, dirt and even rainwater.
  • Sunlight – this breaks up free chlorine in the water in outdoor pools.

So the more people that swim in your pool and the sunnier the weather, the more chlorine your pool requires.

Recommended free chlorine levels

Public indoor pools in the UK aim to keep their free chlorine level between 1.0 and 1.5, however they have sophisticated chemical dosing and control systems. It is normal to keep the free chlorine level in domestic pools (especially outdoor pools) a little higher to give a better margin of safety.  Please see the table below for recommended chlorine levels for pools and spas.

Public Pools with chemical controllers 1.0 – 1.5 ppm
Indoor domestic pools 1.0 – 2.0 ppm
Outdoor pools 2.0 – 3.0 ppm
Hot Tubs and Spas 2.0 – 3.0 ppm

 

Testing for chlorine

Chlorine is the most important chemical to control and is at least 10 times more important than any other test. Therefore it is vital that you test your chlorine level on a regular basis. You can test for chlorine using DPD1 tablets and a chlorine colour comparator or chlorine test strips.

Chlorine Comparator

Testing hints

  • When the chlorine level is very high it can bleach the DPD1 tablet causing you to get a false low reading (see our troubleshooting blog for more information). Usually the water near the tablet goes pink for a short time and then the colour disappears leaving a slight yellow tinge to the sample.
  • This applies to tests on photometers as well as comparators.
  • If you suspect the chlorine level is high carry out a test using a mixture of 1 part pool water and 4 parts tap (or distilled if you have it) water. Multiply the answer by 5.

How do we increase chlorine level in a domestic pool?

To increase free chlorine quickly

Add stabilised chlorine granules or calcium hypochlorite granules (shock).

NEVER MIX STABILISED AND UNSTABILISED CHLORINE IN THE SAME CONTAINER OR SKIMMER AS THEY CAN EXPLODE

  • Add the granules to a bucket of pool water and then add the solution to a deck level drain, strainer basket or direct to the pool.
  • Look at our dosing calculator to work out how much to add to your pool.
  • Be patient – always give it time to mix fully.

To increase free chlorine slowly

To increase chlorine slowly put stabilised chlorine tablets (normally one or two 200gram tablets in a 10,000 gallon pool) in the skimmer or a floating dispenser.

What is the maximum level of chlorine it is safe to swim in?

The UK Pool Water Treatment Group PWTAG – Swimming Pool Water Treatment and Quality Standards – recommends:

  • The pool dosing should be turned off if the free chlorine level reaches 5 ppm.
  • The pool should be cleared of bathers if the free chlorine level reaches 10 ppm.

How do we decrease chlorine level?

By adding sodium thiosulphate solution. This must be done extremely carefully and will be dealt with in a further blog

Introduction to Bromine

By swimmingpoolchemicals.co.uk

Bromine is the most widely used sanitiser for domestic hot tubs and spas. Bromine destroys bacteria, algae, and water-born diseases in much the same way that chlorine sanitises water, however there are a number of key differences between the two.

• Bromine does not form the corrosive by products which cause corrosion of metals in indoor pools

  • Bromine is less volatile than chlorine so it does not evaporate as quickly at the high temperatures which spas operate.
  • Bromine does not form smelly by products, so indoor pools using bromine do not have that typical swimming pool smell. When you have used a bromine hot tub your skin will not smell of chlorine.
  • Bromine does not form the corrosive by products which cause corrosion of metals (including stainless steel) in indoor pools.
  • Bromine does not lose its ability to kill bacteria and viruses at pH values up to 8.2. This is useful on hot tubs in hard water areas where it is difficult to keep the pH down.
  • Bromine cannot be stabilised against breakdown by sunlight, so it is not often used in outdoor pools.
  • Bromine is two and a quarter times as heavy a molecule as chlorine so it is used at a concentration 2.25 times as high as chlorine.

Bromine is normally supplied as white tablets, bromo-chloro-dimethyl hydantoin (BCDMH). In hot tubs these are usually placed in a floating dispenser, which is adjusted to give a bromine level between 3 and 6 ppm. Bromine tablets are very slow dissolving making them very useful in domestic hot tubs. On a hot tub that is used by two people twice a week two tablets in the floating dispenser will keep the water clear and fresh. One extra tablet will need to be added every 7 to 10 days.

Indoor swimming pools usually use an erosion feeder known as a brominator to dose bromine tablets. Because bromine is so slow dissolving it is essential that brominators on busy pools and spas are large enough to meet the bather load. Indoor pools are recommended to maintain a bromine level between 2 & 4ppm.

Bromine is tested using exactly the same test as chlorine using DPD 1 tablets. This is read against color standards in a visual comparator. Since Free Bromine and Combined Bromine are similar in sanitising strength, they both react with a DPD 1 tablet. This reading represents the level of Total Bromine. If a bromine comparator is not available, operators can use a chlorine comparator and multiply the reading by 2.25 to calculate ppm bromine. If you don’t have a comparator bromine can also be tested using bromine test strips.

As mentioned before bromine does not lose its ability to kill micro organisms as pH rises. This means that hot tubs and pools using bromine can use a pH up to 8.2. This is particularly useful on hot tubs and leisure pools where the pH tends to rise if an adequate alkalinity level is maintained.

Preventative action after summer rain storms

By swimmingpoolchemicals.co.uk

After a good start to June the majority of the UK have been treated to heavy storms over the past week. This may have resulted in you forgetting about your pool, however this is often a mistake as pools can go off when there is rain following good weather. The rain washes dust and algae spores into the pool and the dirt uses up the chlorine, allowing  the algae to thrive in the very warm water. The water goes green and it then requires a lot of shocking with chorine and dosing of algaecide to get the pool back to its previous pristine condition. It is therefore important to take pre-emptive action to prevent this by following these simple steps;

  • Give the pool a shock dose of 500grams  of calcium hypochlorite granules (shock chlorine) for every 10,000 gallons of pool water. You can use stabilised chlorine granules if you have an above ground pool.
  • Add an algaecide to your pool.
  • If you use stabilised chlorine tablets or multifunctional tablets put an extra tablet in the skimmer and run the pool at the high end of the chlorine range.

Even though you are unlikely to use your pool during thundery weather, using some extra chemicals now will save you a lot of effort and chemicals in the medium term and it will allow you to use your pool when the good weather returns.

Video – How to clear a green pool

By swimmingpoolchemicals.co.uk

Want to know how to clear a green pool? Check this video out to see how to get your pool from green to clean!

 

 

What is a comparator test?

By swimmingpoolchemicals.co.uk

http://www.totalpoolchemicals.co.uk/images/water_test05.jpg

Comparator Test Kit with Disc

If you are looking for an alternative to test strips when it comes to analysing your pool or spa water then you might consider using a comparator test kit. A comparator is an item of testing equipment used to visually test pool water for parameters such as free chlorine, total chlorine, total bromine and pH. Usually they come in the form of a comparator disc and unit but there are more basic kits on the market that don’t have a disc and just have a colour scale on the side of the test tube.

To conduct a comparator test the first thing you need to do is rinse the test tubes out with tap water. This removes any traces of previous tests that could affect the result. You then need to take two 10ml samples of water. One will be used as a blank in the comparator unit and the other will be used to perform the test. You then need to add the reagent to the sample and crush it using a crushing rod. When doing this you will see that the sample changes colour (if you are doing a chlorine test then it will hopefully turn a shade of pink). Once the tablet has fully dissolved you need to hold the unit up to the light and look through the view finder on the comparator unit and turn the comparator disc until the two colours match. When you have achieved the closest match, read the relevant number off the disc to determine the level in the water.

714M

Basic Comparator Test Kit

There are normally three tests you can do using a comparator and these are;

  • Free Chlorine or Bromine using a DPD 1 tablet.
  • Total Chlorine using a DPD 3 tablet.
  • pH using a phenol red tablet.

If you are using a basic comparator test kit then the process is similar but you don’t use a blank sample. Instead you fill the relevant compartment up with water, add the reagent and then compare the colour of the sample to the colour chart on the face of the compartment.