Learning Centre

Learn more about pool and spa chemicals and equipment

We want to help you get the most from your investment; we have built this Learning Centre so that you can find out more about pool and spa chemicals and equipment and in the process understand how to get the most from your swimming pool or spa.

We are still in the early stages of building the Learning Centre – if you have a question you want answered please go to our Contact section and fill in the form with your question and we will add it to this Learning Centre.

Pool Questions
What are the different types of chlorine that are available for swimming pool use?

There are a number of different types of chlorine available for use in a swimming pool as follows:

  • Liquid chlorine – this is basically a strong version of household bleach sold in larger containers. It is easy to apply as being a liquid it obviously dissolves well.  Some disadvantages are: being a liquid it can splash onto skin, clothes and shoes and leave burn marks, glasses and gloves should be worn when using it; it has a high pH, which has to be offset by adding either liquid or granular acid, it does not contain stabiliser and so will not last long under sunlight; also it has a finite shelf life and loses potency over time, ideally only buy enough to last for a month.
  • Calcium hypochlorite – this is a granular chlorine with calcium being use to form the bond with chlorine. Calcium is needed in the pool, but too much can cause scaling problems.  The correct way to use this chlorine is to put some in a bucket of water, mix it well, wait for a few hours to allow the calcium to come out of solution and settle on the bottom, pour only the liquid into the pool and throw the calcium away.  If your calcium levels are low then you can put all the liquid into the pool.  It has a high pH, so you will need to add some liquid or granular acid to offset this, also it does not contain stabiliser and so will not last long under sunlight.
  • Salt generated chlorine – salt water pools generate their own chlorine by passing the salt water through a “cell” through which an electric current passes and by electrolysis the salt is split into its constituent parts of sodium and chlorine. This is a very convenient way to dose the pool with chlorine, as every time the pump runs and water flows through the cell chlorine is put into the pool water.  However, the chlorine has a high pH and like liquid chlorine and calcium hypochlorite requires the regular addition of acid to keep pH at acceptable levels.  Also it is unstabilised and so will not last long under sunlight.
  • Sodium dichlor – this is a granular stabilised chlorine with sodium being bonded to two chlorine atoms (hence “dichlor”). “Stabilised” means it contains a chemical that ensures that the chlorine will last under sunny conditions.  It has a neutral to low pH and so will not affect this aspect of pool water and its ability to kill germs & bacteria.  Sodium is neutral to pools and the whole of this product can be added to the pool without the need for pre-mixing.  It doesn’t lose potency with time and so can be kept for long periods without detriment.
  • Sodium trichlor – similar to sodium dichlor except there are three chlorine atoms in each molecule. It is available in both granular and tablet form; in the later solid form it is particularly useful for putting in skimmer baskets or tablet feeders where the flow of water over the tablet automatically doses the pool with chlorine every time the pump runs.
What is mineral balance of water?

This is the term used to describe the various chemical parameters that have to be maintained for your pool water. They are:

  • pH – how acid or alkaline the water is, ideal value is 7.5
  • Total Alkalinity – the amount of carbonate buffering capacity in the water. It acts as a “shock absorber” for pH – ideal values are between 80 – 125 ppm for concrete and tiled pools, and between 125 – 150 ppm for all other surfaces.
  • Calcium Hardness – the measure of the amount of dissolved calcium in the water. This naturally occurring element helps prevent concrete and grout etching, vinyl liner wrinkling, and equipment corrosion – ideal values are between 200 – 275 ppm for concrete and tiled pools, and between 175 – 225 ppm for all other surfaces.
How should I add chemicals to my pool water?

Different chemicals should always be added separately to the pool, allowing a reasonable time between each chemical for them to dissolve fully before adding the next chemical to avoid an adverse reaction between different chemicals.  Cloudy water after adding chemicals is usually the result of not waiting long enough between doses of different chemicals.  If a large amount of a chemical is to be

added it is best to divide this into two or three separate doses.  Calcium hardness should be added in this manner as it can be hard to dissolve, especially when the water is warm.

Some chemicals should be mixed with water prior to adding to the pool, be guided by the instructions on the packet or instructions given in your pool water test report.  Chemicals should always be added to water and never the other way round.

What is pH and why it is important?

Simply put pH is how acid or alkaline the water is.  It is defined as a number over a range of 0 to 14, where 0 is the most acidic and 14 the most alkaline.  A value of 7 is considered neutral.  pH is the most important parameter of a swimming pool for a number of reasons:

  • It affects the comfort of people swimming in the water. Ideal value for swimming pool water is 7.5, which matches the pH of teardrops, so that it doesn’t sting the eyes.  Skin tends to have a lower pH, around 6.7, but it is less sensitive than the eyes, however, if the pH deviates markedly from the ideal then you can get itchy skin.
  • It affects the effectiveness of chlorine – see article on I am regularly dosing my pool with chlorine but now it has gone green?
  • It affects the pool and equipment. High or low pH is corrosive and can lead to damage to both plastic and metal parts, especially salt chlorinator cells, as well as vinyl pool liners.
  • It affects the ability of calcium to dissolve in the water. At high pH values calcium doesn’t dissolve well and can come out of solution and cause scaling on pool surfaces, pipes and salt chlorinator cells.
What affects the value of pH?

The following can cause changes in the pool water pH:

  • Rain water – this generally has a slightly lower than neutral pH (around 6.7) and so will tend to reduce ph values. Rain water can also wash out alkalinity from the pool, which will reduce pH and the ability of the water to hold a stable pH value.
  • Chlorine – different types of chlorine have different values of pH as discussed under What are the different types of chlorine? Ensure, if you are using a high pH chlorine, that you add regular doses of acid to maintain the correct value of pH.
  • Chemicals intended to remove metal stains and metals from pool water. This is intentional as metals dissolve in the presence of acids, but be aware that this is happening and test and correct the pH after having removed the metal/stain.
  • Addition of alkalinity – this is a normal part of “mineral water balance” and is offset by adding acid after the alkalinity has been put in the pool.
  • Addition of fill water to top up the pool, especially during summer time when water is lost due to evaporation. The effect on pH will depend on the pH of the fill water.  Test pool water after topping up and correct as necessary.
I am regularly dosing my pool with chlorine but now it has gone green?

You are probably using either liquid chlorine or calcium hypochlorite.  Both of these types of chlorine have a high pH and if you have not been adding some liquid or granular acid after adding the chlorine to offset this then your pH is likely to be quite high.  When chlorine is added to water two types of chlorine are formed, an

active one that will kill germs and bacteria and an inactive one that won’t; the proportion of each being dependent on the pH of the water.  At 7.5ph 50% of each type is formed, at higher pH values less of the active and more of the inactive chlorine is formed; hence there will be less active chlorine to kill algae and the pool will go green.  So it is important when using either liquid chlorine or calcium hypochlorite to add some liquid or granular acid to keep the pH value at about 7.5.

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Seasons Magazine Articles

October 2016

More than a feeling: Quality spa therapy helps

In this article we discuss and explain the many benefits of warm water and hydrotherapy that can be gained from owning a Sundance Spa bought from Maurice’s.

November 2016

Tips for a Summer-ready pool

In this article we explain the steps to be taken in getting your swimming pool ready for Summer.

December 2016

Tips for healthy, sparkling pool water

In this article we discuss the Bioguard 3 Step Programme to give you healthy, sparkling and inviting pool water.

February 2017

How does wind and rainy weather affect my pool

In this article we discuss how weather affects your swimming pool and explain what you can do to address these effects.

March 2017

How to extend your pool season

In this article we discuss and explain the different types of pool heating that are available to help you get a longer swimming season out of your pool.

April 2017

Putting your pool to bed

In this article we discuss and explain what to do when the swimming season has come to a close and you need to prepare your pool for winter.

July 2017

Why a Sundance Spa from Maurice's

In this article we discuss and explain the many features that are considered when purchasing a spa pool and the benefits of buying a Sundance Spa from Maurice’s.

August 2017

Protecting you and your spa

In this article we discuss and explain how to look after your spa by keeping the water balance right and by carrying out some regular maintenance on it.

November 2017

Tips for a Summer-ready pool

In this article we explain the steps to be taken in getting your swimming pool ready for Summer.

This article was repeated from November 2016.

December 2017

How to extend your pool season

In this article we discuss and explain two different types of pool heating that are available to help you get a longer swimming season out of your pool.

February 2018

How to avoid pool problems in hot weather

In this article we discuss and explain the steps to take to ensure your pool stays clear and sparkling during the hotter days of summer, and doesn’t allow algae to take hold and turn it green!!

May 2018

End of pool season and start of spa season

In this article we discuss the steps needed to put your pool to rest over the winter months and to get your spa going for the winter.

June 2018

The three elements of a Sundance hydrotherapy spa

In this article we discuss the benefits of owning a Sundance Spa on your health and well-being.

July 2018

5 Good Reasons to Buy a Sundance Spa

In this article we explain why buying a Sundance spa is a purchase you will never regret.

August 2018

Peace of mind purchasing

In this article we discuss and explain how to go about buying a big ticket item like a spa with the assurance you are going to be satisfied with your purchase.

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