This blog is about swimming pools, spas and hot tubs and how to maintain them.

Looking after your pool in the rain


With all the rain around recently the last thing you have probably felt like doing is going outside for a swim and who could blame you! However it is still important that you look after your pool so when the sun reappears it will be in top condition and ready for you to use.

The reason for this is because during spells of heavy rain the rain washes dust and algae spores into the pool and uses up the chlorine. When the chlorine disappears algae will start to thrive and before you know it you are faced with a horrible green swamp instead of a nice sparkling pool. So instead of enjoying a nice relaxing swim you are having to shock treat it with a lot of chlorine to try and get rid of all the algae.

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 bad 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.

What is Stabiliser?


If you look at your test strips you may notice a pad that tests for stabiliser, but what is it and how does it effect the way you maintain your pool?

A stabiliser is added to the pool water to reduce chlorine loss due to ultraviolet light from the sun. It is usually added to the water via a chemical called cyanuric acid. “According to research results, pools without stabiliser lose about 90% of their total chlorine residual on a sunny day in two or three hours. Pools with 25-50ppm of cyanuric acid, however, under the same conditions, lose only 10 to 15 percent of their total chlorine.” (White et. al. , 1972)

You may not have heard of or even used cyanuric acid before as it is already included in the majority of chlorine products on the market. You may be familiar with chlorine based products such as Stabilised Chlorine Granules, Stabilised Chlorine Tablets or Multifunctional Tablets (a form of the stabilised chlorine tablet). All these products contain cyanuric acid which is why they are referred to as stabilised chlorine. Therefore as well as dosing chlorine into the water they also add cyanuric acid at the same time.

As mentioned earlier only a small amount of stabiliser (25ppm) is needed and the stabiliser level is acceptable up to a level of 100ppm. Once the level exceeds this amount the chlorine becomes less effective. If this happens then you have two choices. You can either switch to an unstabilised form of chlorine such as Calcium Hypochlorite or Sodium Hypochlorite until the stabiliser level drops, or you can replace a proportion of your water. If you choose the latter option then drain your pool by two thirds and replace with fresh water immediately. Do not wait to refill the pool as this could cause damage to the structure of your pool. Always check with your pool builder before emptying your pool.

Indoor pools

If you have an indoor pool that is not exposed too much sunlight, you should consider using an unstabilised form of chlorine such as Calcium Hypochlorite Tablets or Sodium Hypochlorite. There is no need to add cyanuric acid to an indoor pool and if you do the stabiliser level will build and eventually you will have to drain some of your water.

Pool Blaster Catfish Pool Cleaner


SP993MIf you are looking for a pool cleaner that is quick and convenient to use then look no further than the Pool Blaster Catfish from Water Tech.

The Catfish is totally independent from the main pool filtration system which means there is no need for any hoses, cables or additional pumps. It works off a rechargeable Nickel Metal Hydride battery which has a run time of 45 minutes when fully charged. It attaches to all standard telescopic poles making it suitable for all types of pools and spas. It has a 8″ vacuum head and a reusable filter bag which collects leaves, algae and even fine particles such as sand.

It is available for just £139.99 from our website.

Above Ground Pool Chemicals – Water Testing


This week we have taken you through all the major chemical parameters that you need to control on an above ground pool. Now we are going to take you through testing these parameters. Testing your pool water on a daily basis is crucial to provide a clean, safe and comfortable bathing environment for all bathers.

When testing the pool water you are testing for the following:


Reason for Testing: To ensure there is enough chorine in your pool to provide a safe swimming environment.
Recommended Level: 1-3ppm
Level too Low: Open the collar more on your floating dispenser or add stabilised chlorine granules
Level too High: Remove the floating dispenser from the pool and do not add any more chlorine. Remove the pool cover and chlorine will come down on its own.


Reason for Testing: To allow the chlorine to work to its full potential and provide comfortable bathing conditions for the bather.
Recommended Level: 7.2-7.6
Level too Low: Add pH Increaser
Level too High: Add pH Reducer

Other test parameters include Alkalinity and Stabiliser (Cyanuric Acid). The Alkalinity level is not very important on above ground pools but if you are experiencing low levels of alkalinity add a small amount of Alkalinity Builder. If your alkalinity level is too high then it can be reduced using the pH Reducer. As above ground pools are only up for the summer the stabiliser level will not reach a level that will cause concern. In the unlikely event that it does all you need to do is replace a portion of the pool water with fresh tap water.

How do I test for these?

When testing, it is important to have a testing method that is both accurate and reliable. For above ground pools a straightforward testing method such as test strips or a pool tester kit is more than sufficient.

Test Strips

730aTest strips are a popular method of testing the water in above ground pools due to the fact that they are quick and easy way to obtain accurate results. AquaChek test strips are renowned as one of the worldwide leaders in the test strip industry.

The general testing procedure is:

  • Dip your strip into your pool water and remove immediately.
  • Wait 15 seconds.
  • Compare the colour pads to the colour chart on the bottle.

Testing Tips

  • To get the best out of your test strips, store them in a low humidity environment at room temperature.
  • Keep wet fingers out of the bottle to enable accurate results when testing.
  • Do not use any test strips that are out of date.
  • Keep a record of your results, as they can be an excellent reference point when talking to dealers or professionals. They also help you to understand what is going on in your pool or spa.

Pool Tester Kits

An alternative way to test your pool is with a test kit. A test kit normally consists of a clear container split into two sections, one for chlorine and one for 714pH. Each section is filled with pool water and then a DPD 1 tablet is added to the chlorine section and a Phenol Red Tablet is added to the pH section. Once added the water will change colour and this is then compared to the colour chart on the front of the container to obtain your chlorine or pH level.

This week we have taken you through all the important points that you need to be aware of when maintaining an above ground pool. There are other chemicals that you may come across such as algaecide and flocculant and if you would like to find more out about these chemicals you can visit our guide for above ground pools.

Above Ground Pool Chemicals – pH


Day 4 of our guide to maintaining above ground pools looks at pH. Along with the chlorine level, pH plays an important role in providing a comfortable bathing environment in your pool. The pH scale runs from 0 – 14 with 7 being neutral. Anything above 7 is considered alkaline and anything less than 7 is considered acidic. In the context of pool water 7.2 – 7.6 is the recommended level to bathe in.

pH Scale

  • Anything above 7.6 (more alkaline) reduces the effectiveness of the chlorine and can therefore promote viruses and bacteria.
  • Anything below 7.2 (more acidic) makes the water corrosive and uncomfortable to swim in, causing irritation to the bather’s eyes and skin.

Altering the pH Level

To increase the pH level add pH Increaser
To reduce the pH level add pH Reducer

  • Dissolve 45g per 1,000 gallons in a bucket of pool water and distribute around the pool with the filter pump running.
  • Retest after 4 hours.

Tomorrow we will complete our guide to maintaining above ground pools with a look at water testing.

Above Ground Pool Chemicals – Shock Treatment


This week we are taking you through everything you need to know about maintaining an above ground pool this summer. Today we look at shock treatment.

A shock treatment is a boost of chlorine that should be done once a week during the summer or if the pool has problems with algae. You should also do a shock treatment if the pool has been used prior to adding any chemicals. If the pool is used a lot (during holiday periods) and is cloudy at the end of the day it is a good idea to shock it so that it can recover over night.

What should I use as a shock treatment?

For above ground pools it is recommended that you use Stabilised Chlorine Granules or Multi-5 Chlorine Granules as a form of shock treatment. The aim of the shock treatment is to increase the chlorine level by approximately 5ppm to kill any impurities in the water.

Shock Dosing Procedure

  • If you are using tablets and a dispenser remove these from your pool and place in a bucket.
  • Fill a clean plastic bucket with pool water and add the required amount of granules to the bucket. 50 grams will increase the chlorine level by 5ppm in a 1,000 gallon pool.
  • Once this has been thoroughly stirred, distribute it around the pool spreading it around as much as possible making sure it reaches all areas of the pool.
  • It is recommended that you don’t enter the pool until it has returned to its normal range (1-3ppm).

What do I do if my pool goes green?

If your pool goes green you have two choices.

A green pool.

  1. Empty and clean the pool before refilling and treating with chlorine.
  2. Shocking the pool with chlorine and filtering the dead algae out.

The amount of chlorine needed to clear a green pool depends on how green the pool is. However it is better to overdose a pool with chlorine to ensure all the algae is killed. If you do not use enough chlorine you will only kill a small amount of the algae and the remaining algae will multiply rapidly using the nutrients from the dead algae and you are back to square one. All pools are more prone to going green in adverse weather as algae spores and dirt are washed into the pool. To combat this, consider using a debris cover when it is raining.

A very green pool could need as much as 250grams per 1,000 gallons.

Top tips for shock treatment

  • Use stabilised chlorine granules or multi-5 chlorine granules.
  • Shock treat your pool once a week at a time when it is not likely to be used
  • Always dissolve any granular chemicals in a bucket of water before adding them to your water.
  • Always allow the chlorine level to return to 1-3ppm before returning to the water.

Tomorrow we will look at pH in above ground pools.

Above Ground Pool Chemicals – Chlorine


56996 10x10cmThis week we are taking you through everything you need to know when maintaining an above ground pool throughout the summer season. Yesterday we started by giving you a brief introduction into chemicals for above ground pools and today we are going to focus on the most important of those chemicals; chlorine. Chlorine is responsible for killing any bacteria or viruses that get into the water, therefore it is crucial that you treat your pool with chlorine and maintain the correct level of chlorine at all times (between 1 and 3 ppm).

Stabilised Chlorine is predominantly used on small above ground pools as it contains a stabiliser called cyanuric acid, which prevents the chlorine being broken down by the sunlight. There are several ways in which you can dose the stabilised chlorine into your pool water depending on what budget you have and how much work you would like to do.

Stabilised 20g Chlorine Tablets

The recommended way to dose your pool is with 20gram tablets and a floating dispenser. You can either use standard Stabilised 20g Chlorine Tablets or Multifunctional 20g Tablets, which contain an algaecide and a flocculant as well as the chlorine. This enhances the clarity of the water and also assists in preventing algae forming. By using any form of stabilised 20g chlorine tablet you have the peace of mind that you are providing a constant dose of chlorine at all times and hence reducing the amount of work you have to do in order to look after the pool.


Small Floating Dispenser

Dosing Stabilised 20g Chlorine Tablets or Multifunctional 20g Tablets

  • Fill the floating dispenser with tablets.
  • Fully open the blue ring at the bottom.
  • Place the dispenser in the pool and leave it to float around.
  • The rate of dissolution can be controlled by opening and closing the blue ring at the bottom.
  • When the pool is in the use the dispenser is taken out and put into a plastic container well away from the children.

As a general rule if your chlorine reading is towards the latter end of the scale (3ppm) then only have the blue ring open a little and if it is towards the lower end of the scale (1ppm) then open it up more.

Stabilised Chlorine Granules


Stabilised Chlorine Granules

If you are on a tight budget you can use stabilised chlorine granules (sodium dichloroisocyanurate) which is a granular form of chlorine that requires manually dosing. You can either use standard Stabilised Chlorine Granules or Multi-5 Chlorine Granules which contain an algaecide and a flocculant as well as the chlorine. This enhances the clarity of the water and also assists in preventing algae forming. Please note that if you are using Stabilised Chlorine Granules you will need to be more vigilant with the chlorine level to ensure it remains within the recommended range. You may also need to dose the pool regularly to cope with the demand for chlorine.

Dosing Stabilised Chlorine Granules or Multi-5 Chlorine Granules

  • Fill a clean plastic bucket with pool water and add the required amount of granules to the bucket.
  • Once this has been thoroughly stirred distribute it around the pool spreading it around as much as possible making sure it reaches all areas of the pool.

As a general rule 10 grams will increase the chlorine level by 1ppm in a 1,000 gallon pool.

Whichever method of dosing chlorine you use it is vital that you test the chlorine level regularly and maintain the correct level of chlorine in your pool (1-3ppm). We will look at testing your above ground pool in more detail later on this week, however the easiest way to test the chlorine level in your pool is by using a test strip.

Tomorrow we will look at shock treatment in above ground pools.

Above Ground Pool Chemicals – An Introduction

By 10x10cm

We are approaching that time when above ground pools are dusted off and filled for the summer season. Small above ground pools are an excellent form of enjoyment for children (and adults) throughout the summer period. Although they are relatively inexpensive to purchase and straightforward to put up, a lot of people are daunted by the chemicals needed to maintain the pool.

The most important thing to remember is that you DO NOT need to be a chemist to look after a pool. You just need to acquire a little knowledge of what you need to use and why to ensure the pool can be used in a safe and enjoyable environment. This week we will take you through all aspects of maintaining an above ground pool, starting today with a brief introduction.

Why do I need chemicals?

Before you start using any chemicals it is important to gain an understanding on why you need to use chemicals.

  • Chemicals kill any bacteria or viruses that get into the water so they do not multiply and cause infections in bathers.
  • Chemicals prevent you from emptying and re-filling your pool all the time.
  • Chemicals help maintain the clear and sparkling look that you get when you first fill it.

What chemicals do I need to use?

There are several types of chemicals that you will come across when looking after your pool.

  • Chlorine – Kills any bacteria or viruses that get into the water.
  • Shock Treatment – Used periodically to break-up impurities that accumulate in the pool water.
  • Water Balancers – Keeps the water in balance and comfortable to bathe in.
  • Algaecides – Responsible for preventing algae appearing in the pool.
  • Flocculants – Help keep your water looking clear and sparkling.
  • Test Kits – Helps you to keep the right levels of chemicals, protecting both anyone using the pool and the pool itself.

Pool Volume

Before you start using any chemicals it is important that you know the volume of water that your pool holds. This will help you with your dosing amounts. This information can usually be found in the pool instruction manual or alternatively you can visit our website and use our volume calculator.

The filtration system

Adding chemicals alone will not be enough to provide sufficient care for your pool water. You also need to ensure that your pool circulation and filtration system is working efficiently. The majority of above ground pools work in the same way and consist of a pump and filter unit. The pump circulates the water around the pool whilst the filter removes any debris or suspended particles which could cause the water to turn cloudy if left in the pool. The filter unit normally contains a filter cartridge which should be taken out and cleaned regularly.

Please consult your manufacturer’s pool manual for details on your filtration system.

Health and safety

The final and most important part of the introduction process is to know some basic health and safety guidelines for handling chemicals.

  1. NEVER mix chemicals. When adding chemicals add them one at a time and dissolve them in a bucket of warm water before adding to the pool. Once the chemicals are in the water they are fine. Never add water to chemicals always add chemicals to water.
  2. Keep wet hands and dirty scoops out of your chemicals. Contamination is often a cause of problems.
  3. Don’t store pool chemicals where other materials can fall into them.
  4. Use gloves and safety glasses.
  5. Make sure chemicals are locked away from children.

Tomorrow we will focus on chlorine for above ground pools.

Why is there no chlorine in my pool?


A frequent problem that we have customers ring up for is that they can’t detect any chlorine despite adding it to the pool. They add chlorine, test, find none, add more, test…..What is going on? Well, like so many other pool problems, there can be a number of possible causes.

The three most common causes are:

Bleaching of test reagent

In this instance the test reagent being used is bleached out by excessive chlorine levels (normally in excess of 15ppm). If you are using a test strip then the pad will turn white and if you are using a DPD tablet then the sample will remain clear instead of turning pink.

To establish whether this is happening you need to dilute the testing sample. Instead of having your sample made up of 100% pool water, take a sample which consists of 25% pool water and 75% tap water. Carry out the test again and then multiply the result by four to obtain your true level of chlorine in the water.

To reduce the chlorine level you can add Dechlorinator.

Killing algae in the pool.

When a pool goes green the normal method of making the pool water clear and blue again is to add large amounts of chlorine. This is known as shocking the pool. In the process of killing the algae the chlorine is used up and although it appears that you are adding chlorine and it is just disappearing.

Sunny weather and no stabiliser.

Chlorine is broken down by sunlight. This can happen quite quickly even in a British summer making it very difficult to keep free chlorine in the water. The answer is to add a stabiliser or use a sanitiser with a stabiliser included such as Stabilised Chlorine Granules or Stabilised Chlorine Tablets.

Cloudy Swimming Pools


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.