Pool, Spa and Hot Tub Maintenance: Understanding Chemicals and Water Quality

Why Pool and Spa Water Must be Balanced

Serious- even life threatening- illnesses can be spread by water that is not properly maintained. Your expensive pool or spa and all of its equipment is under threat from unbalanced water. Also the water just gets plain yukky! By that highly technical word, I mean, algae, slime and unpleasant smells become an unwelcome part of your swimming experience.

Things to Monitor Regularly

Keeping water in a swimming pool or spa healthy and balanced is a question of understanding what is in the water, how the various chemicals can be measured and what needs to be added to get things to the right level.

There are five important properties of pool spa and hot tub water that need to be routinely monitored: the sanitiser, total alkalinity, pH level, hardness, and total dissolved solids. With the right chemical kit or test strips these can be measured quickly and easily.

The difficult part comes when you adjust one of the components and find that it has affected other components in a way that you don't want. This is why people talk about 'balancing the chemicals' in a spa or hot tub. Get the proportion of chemicals right and the water is balanced, healthy, safe and fresh. This needs a little practice but is pretty simple once you grasp the essential facts.

First off, it's worth looking at the kind of chemicals used in pool spas and hot tubs and what their job is.

On this Page

• Sanitizers - Chlorine, Bromine, Biguanides (eg Baquacil, Soft Swim)
• Chlorine and non-chlorine 'shocks' to clear out organic contaminants
• Non-Chemical Sanitizers- ozone and ionisers
• Acids and Alkalis
• Total Dissolved Solids
• Total Alkalinity
• Water Hardness
• Links to test kits and practical step by step guides to managing water quality.

Sanitizers

Sanitisers do what they say they do. They kill bacteria and anything else in your pool or spa that might threaten your health. They also help to stop algae growth.

Chlorine Sanitizer

The commonest and cheapest sanitizer is chlorine. For spas and home pools, chlorine comes in a liquid or solid form. Larger pools may use chlorine gas.

Liquid Chlorine

Liquid chlorine is sodium hypochlorite dissolved in water and has the advantage of being cheap and very easy to use. The typical spa product has about 12% of available chlorine. The rest is water and sodium chloride (common salt). Sodium hypochlorite is also the main ingredient in normal household bleaches but don't use household bleach as a sanitiser unless you are sure it contains nothing but sodium hypochlorite. Many brands of household bleach contain detergents or phosphates which will promote algae growth.

When the chlorine comes into contact with any organic material like bacteria or dead skin flakes the chlorine attacks the organic material and breaks it down (technically, it oxidises it). The common salt- Na Cl- remains behind in the water.

In storage, it needs to be kept cool and away from sunlight. Liquid chlorine should be used within a few weeks of purchase.

Calcium Hypochlorite

This is available in granular or tablet form. Like liquid chlorine, it deteriorates in sunlight or hot conditions. It is relatively slow dissolving and can leave unsightly mineral residues in the water-often it is sold in a fabric bag to prevent this from happening. It is 65% chlorine and will make water more alkaline.

Dichlor (Sodium Dichloro-s-Triazinetrione)

This is a solid product with about 60 per cent available chlorine. It is weakly acidic. This is a popular choice for home use, as it is stable, doesn't affect water pH too much and is safer than the Trichlor described below.

Trichlor (Trichloro-Triazinetrione)

This product usually comes as tablets or sometimes as granules. It is slow dissolving which can be an advantage if you want to keep water fresh while you are away. It is often used in automatic sanitizer delivery systems.

It has 90 per cent available chlorine and is the most expensive of the chlorine sanitising products. It is also the most highly acidic and pH will need to be adjusted whenever it is used.

For professional spa and pool technicians, this is the chemical of choice for tackling serious algal problems. It also has the advantage of being very stable so it can be kept for long periods without deteriorating.

Safety Issues with Chlorine Sanitizers

All strong chlorine solutions will attack skin and natural clothing (eg cotton or wool) and should be treated with respect. Gloves and eye protection are recommended for handling very strong chlorine solutions. Trichlor is a lung irritant.

Cyanuric Acid Stabilizer

Cyanuric acid stabilizer (sometimes called 'conditioner') helps maintain levels of free chlorine in the pool or spa water. Without CYA, up to 90% of free chlorine can be destroyed by sunlight in as little as three hours.

CYA Levels should be between 30 and 80 ppm. Too much will stop the chlorine working at all and too little won't offer enough protection.

Chloramines, Free Chlorine and Total Chlorine Load

Chloramines are formed when chlorine reacts with ammonia from sweat or urine in the water.These are the chemicals that give the strong smell and stinging eyes associated with chlorine use. If water is well maintained, chlorine sanitizer will cause little irritation.

Chloramines don't kill bacteria so ammonia is said to 'tie up' chlorine. Only the free chlorine is able to act as a sanitizer.

To manage a hot tub or spa successfully it is important to know both the free chlorine levels and total chlorine levels. High total chlorine indicates the need for a chlorine 'shock' (see below).Test strips from your local or online supplier allow you to measure free and total chlorine quickly and easily.

Different Folks, Different Names

One area of confusion in spa and hot tub maintenance is that people use a lot of different names when talking about the same thing. When it comes to chlorine sanitizer, this is especially so.

Free Chlorine=Available Chlorine=Residual Chlorine

Total Chlorine=Chlorine Load= Combined Chlorine.

There are only ever two chlorine measurements to worry about in pool or spa water. Just pick a name for each and stick to it!

Chlorine Shock (or Super Chlorination)

Spas and hot hubs need a regular 'shock' treatment to clear out organic material. Chlorine shock is OK to use where either chlorine or bromine is the sanitizer. With biguanide sanitizer always use hydrogen peroxide as a shock (see below).

A chlorine shock needs to be applied at anything from weekly to monthly intervals depending mostly on bather load. Check packaging of your chlorine product for doses. 10 ppm of free chlorine is usually strong enough as chlorine shock. Non-chemical sanitizer systems like ozone generators and ionizers reduce the need for shocking.

Essentially, a shock is needed whenever there are any obvious problems with water quality such as cloudiness, smell or algae and is a good idea after any heavy use of the pool, spa or hot tub.

After a chlorine shock, keep people out of the water for at least 24 hours and test the water to make sure it has returned to less than 5 ppm of chlorine before giving the all clear to users

Non-Chlorine Sanitizers

Bromine

This is used as an alternative to chlorine when people don't like the odors produced by chlorine. It is also more stable than chlorine at the high temperatures found in hot spas. It can be applied in granular or stick form. A small amount of chlorine is often used as a catalyst (ie to activate the bromine) but non-chlorine catalysts are also available.

One advantage of bromine sanitizer is that when the bromine is 'tied up' by organic contaminants or ammonia from sweat etc, it can be easily revived. Shocking once a week or so (depending on the number of bathers) with chlorine or non-chlorine shock will bring free bromine levels up, without necessarily having to add more bromine.

The ideal range for bromine is 2.0 to 4.0 ppm.

If you overdose with bromine, the levels will fall fairly slowly. Supply shops sell chlorine and bromine neutralizers if you need a quick reduction.

Biguanide eg. Baquacil, Soft Swim

To use this sanitizer effectively read all the instructions that come with the product. The normal regime is a monthly shock with hydrogen peroxide and weekly doses of Biguanide to maintain a level between 30 and 50 parts per million (ppm). Dissolved metals need to be removed from the spa or hot tub (with something like 'metal out') and great care used with cleaning agents.

Introducing any product containing chlorine into the water can result in brown, discoloured water and deposits on the sides of the spa. It is not compatible with ozone generators.

Advantages and Disadvantages of Biguanide

Biguanides are not usually recommended for spas or aerated pools.

Fans of biguanide sanitizer say it is less irritating to skin, eyes and nose. They also point out that it is more stable so that water needs less maintenance. Detractors claim that biguanides are not as effective at killing bacteria and it is difficult to be sure that the correct levels are present in the water. Filters choke up more quickly and need cleaning more often.There is an interesting discussion between pool users here: http://wiki.answers.com/Q/Is_chlorine_or_baquacil_better

Non-Chemical Sanitizers

Ionizers

Copper ions are effective in killing algae. Silver ions are effective in killing bacteria. Ions are simply electrically charged particles that are generated by placing electrodes in the pipework connected to a low voltage dc supply. They can cause staining on pool and spa surfaces if not properly managed.

Ozone

Introducing ozone into the water will kill bacteria and reduces the amount of water sanitiser required.It improves the smell, feel and clarity of the water and helps clear scum and oils.

Ozone is generated by either passing air over a powerful ultraviolet light or by passing it through a corona discharge (a sort of lightening storm in a box). The high energies convert ordinary oxygen into ozone, a very reactive molecule that attacks organic material.The need for sanitizer is reduced not eliminated.

Other Important Water Properties

Acids and Alkalis

pH is the scale used to measure how acid or alkaline water is. 7 is neutral. Anything less than 7 is acidic, anything above 7 is alkaline. Spas and swimming pools need to kept between 7.2 and 7.8.

If spa or pool water becomes too acidic, the water will attack and corrode metal fittings, sometimes leading to water discolouration. If water become too alkaline it encourages scale to form on the pool or spa sides and equipment. Heater failure is a common result.

pH also has health implications because it has an impact on how well sanitizers work.

Acid- either in liquid or granular form-is used to adjust pH. Test kits for pH are available from spa and pool supplies stores. Adding too much acid means you will need to correct with alkaline products like 'alkahli up'.

pH anchors can be used to lock in pH levels but these affect your ability to adjust water hardness.

If the pool or spa has plastered or tiled walls, alkaline lime in the plaster or grout is constantly dissolving so more monitoring of pH may be needed.

Total Alkalinity

This is a measure of all the chemicals in the water that have a potential to be alkaline. This needs to be measured and the alkaline materials (like dissolved lime) need to be neutralized before pH is adjusted. This will save a lot of sanitiser and acid use in the long run. Alkali neutralizers can be bought from any good spa or pool supplier. Excess alkalinity will contribute to lime scale deposition which in the worst cases blocks jets and pipes. Total alkalinity outside of the normal range can make pH fluctuate wildy.

Total Dissolved Solids (TDS)

TDS is a measure of all the chemicals in a spa and is easily monitored with test strips. It increases with time as more and more chemicals are added and also as a result of evaporation. Once TDS exceeds 2000 ppm, balancing a pool is difficult and requires excessive chemical use. The pool needs to be drained partially and refilled with fresh water.

Never drain a pool with a vinyl liner by more than a third. The liner will shrink and, instead of stretching when the water is replaced, it will tear.

Tap water containing a lot of dissolved calcium salts is usually called 'hard' because it is difficult to produce a lather with soap.

Water hardness can affect pools in two ways. If the water is too soft it can gradually dissolve metal fittings and cause water discolouration. If it is too hard it can result in scale deposits on pool or spa surfaces.

Water hardness can be measured with test strips and adjusted with products like Water Hardness Increase or Scale and Stain Control (decreases water hardness). If you use a pH anchor to maintain a constant pH do not use these products. Reduce water harness by draining the pool and refilling.

More on water hardness:

http://www.swimming-pool-care.com/calcium-hardness.html

Water Hardness

Water is said to be hard when it contains a lot of calcium or magnesium salts. The most obvious sign is that it is difficult to get a lather when washing with soap.

Water that is very soft can slowly dissolve metal components in pipework and pumps. In plaster-walled or tiled pools and spas it will dissolve cement and grout. Water that is very hard will deposit lime scale, clogging pipes, jets and filters. If left unchecked lime scale can cause failure of pumps and water heaters.

Water softening agents are available but often the only way to reduce water harness is to drain or partially drain the water and refill with fresh. Calcium chloride can be added to increase water hardness.

If you use a pH anchor, avoid using water hardness adjusting chemicals.

More on Water Hardness:

http://www.swimming-pool-care.com/calcium-hardness.html