Section 11 – Pool Water and Tile Installation Maintenance
11.1 Fill and Drain Rates
Swimming pools and fountains which have had tile and stone installed should be filled and drained at a prescribed rate of 1" (25 mm) per hour. Following this prescribed fill rate will help to alleviate the rapid expansion of the pool walls due to the weight of the water, moisture expansion of the tile and thermal gradient variation. Maintain a differential of 10°F (5.5°C) or less between the fill water and substrate temperatures during fill cycles. While the movement joints and sealant will accommodate most of this movement they will be stressed during the fill period so a slow fill can help the movement joints better fulfill their intended purpose.
During the drain periods the slow rate will allow the movement joints and tile system to shrink back at a slower and safer rate. As the tile or stone, immersed in water for extended periods, dry out they will experience shrinkage movement due to the loss of moisture. The weight of the water in the pool goes down and the walls can shrink back due to the loss of pressure. The slow empty rate allows for a normal process to take place without damage to the pool or tile system. The slow drain rate also helps to prevent hydrostatic pressure from causing delamination of tile in pools without a waterproofing membrane.
NOTE: The prescribed fill and drain rate described above is recommended for pools, fountains and water features which have received a tile or stone installation. Filling or emptying these vessels which have received other finish types may not be necessary or recommended. Please check with the finish material manufacturer for their recommended fill and drain rates.
While the prescribed rate of 1" (25 mm) per hour is rather slow, damage caused by filling or emptying too quickly can be far more time consuming and costly than waiting a few days longer to fill the pool.
Initial alkalinity of pool water may be very high, due to exposure to plaster, grouts and mortars so careful and frequent balancing of the pool water is required. The pool or fountain should not be filled if potential thermal gradients are present (e.g. very cold water source, pool exposed to direct sunlight for extended periods, etc…).
11.2 Opening and Closing Seasonal Swimming Pools and Water Features
Opening – Opening a swimming pool, depending on the climate, is an annual rite of spring for pool owners. The process of opening a swimming pool involves many different tasks and allows for routine inspection and maintenance to be performed.
For swimming pools in northern climates the list includes;
Removing, Cleaning and Storing the Pool Cover
Testing Water Balance, pH, Calcium, Cyanuric Acid, Calcium Hardness, and Alkalinity Levels
Inspecting Electrical Service, Filters, Ladders, Diving Boards, Plugs, Gauges, and Other Important Components of the System
Lubricate Fittings, Valves, O-Rings, and Plugs
Inspect Tile and Grout Installations, and Clean Tiles and Skimmer With Cleanser
Clean and Inspect Pool Deck
Skim Pool Water Surface and Vacuum Pool Bottom
Backwash Filter if Necessary
Shock Pool Water to Breakpoint Levels
Failure to inspect and correct any problems during the opening may result in down time of the pool during the warmer season when the pool will be utilized the most.
For swimming pools in southern climates, where the pool will be open year round, it is still necessary for an inspection and maintenance regimen to be followed. This will help keep the pool sanitary and safe for the users and prevent significant down time due to improper upkeep.1
In many cases a professional pool maintenance company is utilized to make sure that the pool is running efficiently, the pool mineral and chemical levels are properly maintained, and that the entire pool system is working properly.
Closing – Closing a pool for the winter is also a common sight in cold weather climates. The process of closing a pool is just as important to the long term performance of the pool as the opening. Some of the steps to closing the pool properly typically include (check local guidelines for proper pool closing requirements);
Balance the Pool Water Chemistry
Remove Skimmer Baskets, Cleaners, Ladders, Wall Fittings, and Solar Blankets From the Pool
Lower the Water Level in the Pool to Below the Skimmer Level in the Pool
Drain All Pumping, Filtering, Heating, and Sanitizing Equipment to Prevent Damage Caused By Breezing
Lubricate O-Rings, Valves and Plugs to Make Opening the Pool in the Spring Easier
Clean and Vacuum the Pool
Winterize the Plumbing by Blowing Out the Lines and Plug the Lines With Expansion Plugs
Add Winterizing Algaecide
Cover the Pool With a Tight Fitting Cover
In warmer climates many people simply reduce the amount of filtration times per day and also find that the pool requires fewer chemicals. As the use of the pool decreases, the opportunity to inspect and provide maintenance to the pool increases.2
NOTE: It is important to note that swimming pools and water features which are in use year round also require the same regular attention and maintenance as seasonal swimming pools and water features.
11.3 Water Treatments and Tile Installations
It is not the goal of this manual to provide advice or recommendations for the proper treatment of swimming pool, fountain, water feature, or spa water. The best advice that we can offer along these lines is to consult with a pool professional who knows the water conditions and best water treatment options available for your pool and geographical region. For more information on locating a qualified pool professional in your area, please contact The Association of Pool and Spa Professionals at www.apsp.org.
To get a better understanding of pool water balance we will look at several aspects of water treatment;
Sanitizers – A pool sanitizer and its accompanying shock is commonly referred to as either a sanitizer, a disinfectant or an oxidizer, but, these products must be able to perform all 3 tasks.
Sanitizing – Killing all bacteria, living organisms and other contaminates that are present in water
Disinfecting – Kills all potential disease-carrying capabilities of these bacteria, living organisms and other contaminates
Oxidizing – Oxidizes any ammonia that is present in the pool due to environmental factors, fertilizers blowing into the pool, or swimmer waste (e.g. urine, saliva, perspiration, suntan lotions, saliva, body oils, etc…). Ammonia is usually only oxidized using a pool shock suitable for use with the sanitizer being used in the pool
There are currently several methods for sanitizing pools, fountains and water features;
Chlorine – Chlorine is the most commonly used pool sanitizer in the industry today. Chlorine will take a leadership role in sanitizing, disinfecting and oxidizing when present in any water. Unfortunately, it is not as easy as adding chlorine to your pool from time to time, expecting the water to stay crystal clear and sparkling. The chlorine levels must be monitored on a continual basis based on environmental conditions (e.g. temperature, humidity, sunlight, rain, wind, and evaporation) and bather load. Failure to do so can cause the water to turn murky and green with the growth of algae.
For a better understanding of chlorine and how it works we will look at some terminology regarding this type of chemistry;
Chlorine Demand – The amount of chlorine needed to kill bacteria, living organisms and other pollutants in the water.
Free Chlorine – The chlorine not presently being used to kill bacteria, living organisms or other pollutants in the water.
Chloramines – Formed when chlorine combines with ammonia in pool water. Chloramines are ineffective at sanitizing, disinfecting and oxidizing pool water.
Total Chlorine – The combined reading combination of Free Chlorine and Chloramines.
Chlorine levels are measured on two scales; Total Chlorine and Free Chlorine. The results of testing for Total Chlorine tells you when to shock the pool to get rid of excess chloramines and ammonia, and, the test results for Free Chlorine tells you when to add chlorine to the pool. When chlorine is added to water, a dissociation occurs. In other words, Cl2 (chlorine) + 2H2O (water) = HOCl (hypochlorous acid) + HCl (hydrochloric acid). Hypochlorous acid is the active by product of this reaction that is responsible for killing bacteria, living organisms or other pollutants in the pool water. The chlorine molecule or ion kills microorganisms by entering through cell walls and destroying inner enzymes, structures and processes. When this occurs the cell is effectively deactivated or oxidized. The hypochlorous molecule or ion continues working until it combines with a nitrogen or ammonia compound, becoming a chloramine, or is broken down into its component atoms, becoming deactivated itself.
Chlorine is available in many forms for use in a swimming pool;
Granular Chlorine – Granular chlorine has many advantages; it is fast dissolving, typically has 63% available chlorine, contains cyanuric acid, has a long shelf life, has a pH level of 6.8 (fairly close to the desired level), does not add any by-products to the water, and can be used both for sanitizing and shocking. Disadvantages include a cost higher than chlorine tablets and less available chlorine than tablets
Chlorine Tablets – Easily the most common form of chlorine sold for pool treatments. Chlorine tablets contain about 90% available chlorine, contains cyanuric acid, have long shelf life, and are less expensive than granular chlorine. The disadvantages are few and are easily corrected. Chlorine tablets have a pH between 2.8 – 3.0, which can lower the pH level in the pool water. If the pH level is not monitored and corrected often then degradation of metal in the pool, as well as cement based tile and stone installation materials (e.g. grout) can occur
Liquid Chlorine – Liquid chlorine is inexpensive, easy to use, and begins working immediately after it is added to the pool or fountain. Disadvantages include the fact that liquid chlorine provides only about 12 – 15% available chlorine which can be exhausted quickly due to exposure to sunlight and a short shelf life. The use of liquid chlorine may also add unwanted salts to the pool water (a result of the production process of the liquid chlorine)
Chlorine Gas – Chlorine gas is reasonably inexpensive, provides 100% available chlorine and adds no by-products to the pool water. This form of chlorine is rarely used in swimming pools mainly because of its one significant disadvantage – if misused, chlorine gas is deadly. Chlorine gas is difficult to handle, making misuse easy
Cyanuric acid is a necessary addition to any pool treated with a chlorine product. Chlorine tablets and granular chlorine are Cyanurates, which simply means they contain cyanuric acid. Typically sold as either “Conditioner” or “Stabilizer” cyanuric acid protects chlorine from being destroyed by sunlight. Cyanuric acid needs to be added whenever a pool is drained, cleaned and refilled because tap water contains almost none of this chemical. The recommended range for cyanuric acid is 30 – 80 ppm (30 – 80 m with a maximum of 100 ppm. If the level of cyanuric acid rises above 100 ppm the only way to achieve a suitable reading is to drain the pool completely and refill with new water. Cyanuric acid has a pH of 4.0, so if the pH level is not monitored and corrected often then degradation of metal in the pool, as well as cement based tile and stone installation materials can occur.
Bromine – Bromine is an effective alternative to chlorine that comes in both tablet (far more commonly used) and granular forms. Bromine is far more stable at higher temperatures, and, as such, is used more often than chlorine to sanitize, disinfect and oxidize spas. Due to the presence of ammonia in pool water, bromamines (like chloramines) will be present in pool water. But, unlike chloramines, bromamines are at least marginally effective at assisting in sanitizing, disinfecting and oxidizing the water. Unlike chloramines, bromamines will breakdown by themselves but they should be removed from the water by regular shocking to maintain a stable water environment.
The main drawback of bromine, coupled with its non-chlorine shock, Potassium Peroxymonosulfate (required to get rid of ammonia and bromamines), is its expense. Bromine is more expensive than chlorine and only equally effective at producing results. Another drawback is that it will be destroyed by sunlight and that it cannot be protected by the use of cyanuric acid. Bromine has a pH of 4.0, therefore, constant monitoring of the pool water will be necessary to avoid possible problems caused by low pH (acidic).
Bromine by itself, cannot oxidize. In other words, to be effective, bromine requires a catalyst; and the catalyst is often chlorine. The tablet mixture is typically around 60% bromine, 28% chlorine and 12% inert ingredients. Bromine levels should be maintained at 2.5 – 4.0 ppm (2.5 – 4.0 m with an industry accepted minimum level of 2.0 ppm (2.0 m
. It is best to add bromine when the level reaches 2.5 to avoid any potential problems.
Figure 11.1 – Diagram of how ozone is created by an ozone generator.
Salt Water – Salt water pools are becoming more and more prevalent, and this method of sanitizing a pool is very effective. A salt water pool has 3 main components; salt, a salt cell and a control box.
First, it will be best to explain that the level of salt used to sanitize a swimming pool or fountain is not the same as ocean salt water. Ocean salt water contains about 20,000 ppm (20 m of salt, while a salt water pool contains only about 3,000 ppm (3 m
. At 3,000 ppm (3 m
you generally cannot even taste the salt; in fact, your eyes contain about 9,000 ppm (9 m
of salt. Any water under 6,000 ppm (6 m
is still considered fresh water.
A salt water pool system works to sanitize a pool based on the fact that chlorine can be produced by running the salt water through a series of plates (the salt cell) with opposite electrical charges. As the water passes through these plates electrolysis takes place which releases the chlorine in the salt. The control box sends electricity to the salt cell and controls how much chlorine is produced by regulating how long the electricity is applied to the cell.
Salt water pools do not have the ability to shock the pool water so a chlorine shock (super chlorinator) is used to quickly raise
the chlorine level when necessary. Cyanuric acid would also be required at 30 – 80 ppm (30 – 80 m since chlorine is the end result of the salt water electrolysis process. Another benefit of salt water pools is that the water is softer, since salts are commonly used to soften water. Salt water may have an effect on a tile or stone installation system as well as many other cement based finishes; efflorescence.
Figure 11.2 – A typical salt water circulation and treatment system4.
There are other water treatment options but these are used infrequently, and will not be mentioned in this text. However, choosing the water treatment option best suited for your conditions is very important and the decision should be after consultation with a qualified pool professional.
Supplemental Sanitizers
Ozone – In its natural state, ultraviolet (UV) light from the sun converts oxygen molecules into ozone molecules. Ozone is the earth’s natural purifier and cleaner; and this fact makes it a perfect choice to assist in the sanitization of swimming pool water. Ozone is a supplement to be used with chlorine or bromine to fully sanitize the pool water. In combination, the end result is crystal clear, sparkling water at a fraction of the cost of using chlorine and bromine alone. In fact, ozone has been proven to purify, clean and sanitize pool water faster and more effectively than traditional chlorine or bromine alone.
When used in conjunction with chlorine or bromine, ozone will kill or get rid of all bacteria, living organisms, ammonia, swimmer wastes, algae, dirt, debris, and other contaminants virtually on contact. This is done with no odor and without leaving any by-products in the water, other than oxygen.
The ozone sanitizing process works by placing an ozonator in line with the pool circulation equipment after the filter. Water flows through the pump and passes through the filter where any dirt, debris or particles are trapped. The water continues through the heater (if present) and then through the ozonator where the water will be exposed to a specific wavelength of UV light. The UV light converts oxygen molecules into ozone molecules where the water is cleaned naturally.
Ultraviolet Light (UV) – UV lamps are useful for supplemental sanitation in swimming pool and spa water. Although UV light is very effective against microorganisms, UV lamps cannot be used as stand-alone sanitizers since they do not impart a sanitizer residual into the water. As such, UV lamps can only be used in conjunction with a suitable EPA registered pool water sanitizer to ensure bathers are protected against disease and infection. For the UV lamp to be effective as a germicide it must emit UV light wavelengths in the 200 – 310 nanometer (nm) which is in the UV-C range, and to a lesser extent UV-B.
UV light inactivates microorganisms by damaging their nucleic acid, thereby preventing the microorganism from replicating which thereby prevents infecting a host.
Pool Water Chemistry
Water, by itself, is rarely free of harsh minerals and various chemicals or contaminants (e.g. bacteria, ammonia, living organisms, and other pollutants). Some of these contaminants are evident in the water used to fill the pool, some come from certain environmental factors, and others result from pool chemistry. The fact is that the majority of these minerals and impurities must be eliminated from your pool. To do this requires the addition of certain chemicals to combat the undesired effects caused by the contamination, and to have the proper amount of minerals to achieve “balanced water”. Alkalinity, pH, and hardness are your water balancers and are responsible for creating optimal water chemistry. If these levels are within their desired ranges, if water circulation is adequate, and a proper maintenance program is followed, the result will be clean, clear sparkling blue water.
When water is considerably less than saturated (minerals) it is said to be in a corrosive or aggressive condition. When water is over saturated and can no longer hold the minerals in solution it is in a scaling condition. Balanced water is that which is neither over-saturated nor under-saturated. Water which is under-saturated will attempt to saturate itself by dissolving everything in contact with it in order to increase its own mineral content. Water which is over saturated will attempt to rid itself of this content by precipitating minerals out of solution in the form of scale. This gives a whole new meaning to the phrase “water seeks its own level”.3
pH – Although a pH of 7.0 is considered “neutral” for everyday water, it is not ideal for pool water. The ideal pH range for pool water is 7.2 – 7.8, with pH of 7.4 – 7.6 being optimal. Therefore, for a swimming pool, the pH scale has to be revised:
A pH Level Between 1.0 – 7.19 Will Be Considered Acidic (Having a Low pH)
A pH Level Between 7.2 – 7.8 is Good For Pool Water
A pH Level Between 7.81 – 14.0 Will Be Considered Alkaline (Having a High pH)
The pH affects three key aspects of pool operation as well as swimmer comfort and safety:
Water maintained within the range of 7.2 – 7.8 is generally not irritating to eyes and skin.
The pH range of 7.2 – 7.8 is good in terms of the sanitizing and oxidizing efficiency of chlorine sanitizers. At higher pH, only a small fraction of the free available chlorine will be in hypochlorous acid form, and hypochlorous acid is far more effective as a sanitizer and oxidizer than is hypochlorite ion. At lower pH, chlorine gas may form resulting in inefficiencies due to chlorine loss and possible breathing hazards for occupants. The effectiveness of other sanitizers (e.g. bromine, Polyhexamethylene biguanide [PHMB]) is not dependent on pH.
pH is a key driver in maintaining water balance by avoiding conditions in which the water is excessively corrosive to plumbing and pool surfaces, or, predisposed to deposit scale on exposed surfaces.
pH can be raised or lowered with the addition of certain chemicals. Sodium Bisulfate is commonly used to reduce pH and Sodium Carbonate is commonly used to raise pH. At the conclusion of all surface preparation and prior to the installation of tile, measure the pH level of the substrate. This work should not commence until the pH value is 10 or less.
Total Alkalinity – Alkalinity is often confused with pH as a unified and singular water-balancing chemical. While alkalinity has a definite affect on pH, they are certainly not the same. A pH test will show the acidity or alkalinity of water, while the Total Alkalinity test will show the quantity of alkaline material in the water. Some alkaline material is required in the water to maintain proper water chemistry. Both pH and Total Alkalinity play a role in achieving and maintaining water chemistry; therefore both must be adjusted on a regular basis. It should also be known that the Total Alkalinity level must be adjusted first and then the pH. This is because Total Alkalinity is a measure of the pH buffering capacity of the water (the ability of the water to resist pH change); if Total Alkalinity is in range, the pH is far less likely to fluctuate. For adequate buffering of the pool pH, a Total Alkalinity level of 60 – 180 ppm as calcium carbonate (CaCO3) must be maintained. Ideally, the Total Alkalinity level should be between 80 – 100 ppm as CaCO3 where calcium hypochlorite, lithium hypochlorite and sodium hypochlorite are used because these sanitizers will cause the pH to rise.
Total Alkalinity is generally expressed in terms of the equivalent concentration of calcium carbonate in mg/L (or ppm). For protection of calcium based materials (cement based grouts, cement plasters, etc…) within the pool, it is important to maintain sufficient carbonate alkalinity.
Calcium Hardness – The Calcium Hardness of pool water is the measure of primarily calcium and magnesium combined. Maintenance of Calcium Hardness in the recommended range helps to keep water balanced per the Langelier Saturation Index, influencing the water’s corrosiveness or tendency to scale, depending on the degree of calcium saturation. Low levels of Calcium Hardness are not as important for non-cement based surfaces, but, regardless of the pool surfaces, it is important to keep the calcium concentration below the maximum to avoid production of scale and cloudy water. Problems associated with low Calcium Hardness levels affecting the grout can be avoided by using LATICRETE® SpectraLOCK® PRO Grout† instead of a cement based grout.
Pool water Calcium Hardness shall be maintained between 150 – 1000 ppm as CaCO3, and ideally between 200 – 400 ppm for swimming pools. In spas, Calcium Hardness shall be maintained between 100 – 800 ppm as CaCO3, and ideally between 150 – 250 ppm.
Typically, Calcium Hardness levels should be maintained between 200 – 450 ppm (0.2 – 0.45 m with a maximum of 500 ppm (0.5 m
. Maintaining Hardness levels within the accepted range is important and levels too high or too low can lead to a variety of problems.
If the Hardness level gets too low these problems may occur;
Dissolved Metallic Parts of Your Pool
Stained and Etched Concrete or Cement Products in Your Pool (Including Cement Based Grout)
Stained Liner in Vinyl-Lined Pools
Blistering or Delamination of Fiberglass in Fiberglass Pools
Minimizes the Effects of Chlorine or Bromine
Foam
Eye and Skin Irritation
If the Hardness level in a pool is too low it can be raised with the addition of Calcium Chloride.
If the Hardness level gets too high the following problems can occur;
Cloudy Water (Turbidity)
Scale Formation (Heavy Metal Minerals in Suspension Which Form Deposits on Interior Pool Surfaces)
Poor Filtration (Caused by Scale Build up in Plumbing Which Restricts Water Circulation)
Minimizes the Effects of Chlorine
Eye and Skin Irritation
If the Hardness level is too high then lowering it should be done immediately, but, it is not possible to lower the Hardness level with the addition of a chemical or treatment. The Hardness level can only be lowered by draining the pool, either partially or completely. The use of a Metal Sequestering Agent is recommended to rid the water of the excess minerals which lead to elevated Calcium Hardness levels.
Figure 11.3 – Heavy metals found in pool water, their sources and scale or water color with excessive levels5.
Total Dissolved Solids – Total Dissolved Solids is a measurement of the total amount of matter (minerals, chemical residue and other particles) that remains in water after evaporation.
Total Dissolved Solids (TDS) – Total dissolved solids is a measure of all dissolved ions (total amount of solid matter) in the water and may or may not indicate a problematic condition. The following will contribute to TDS: source water, rain water, treatment chemicals, and bather waste. As water evaporates, only the water itself evaporates while the particulate matter (solids) remains in the pool water, thereby increasing concentration. High TDS levels (1500 ppm and above) may correlate with the presence of undesirable substances that may cause poor water quality and indicate the need for water replacement. It is necessary to replace water lost to evaporation with tap water, or other source, as well as additional chemicals. However, this new addition of water and chemicals will increase the TDS in the water.
This process will continue for extended periods and the TDS will continue to rise. However, if the amount of solids in the pool water gets too high then the particulate matter will act as a sponge and minimize the effects of new pool chemicals added to the water. Typically, it takes 6 – 8 years for the TDS level to reach a critical level, and the only way to correct the problem is to empty water from the pool and replace with new water and chemicals.
Salt water pools intentionally have high concentrations of sodium chloride which contribute to TDS, but will not cause decreased sanitizer efficiency or cloudy water.
If the Total Dissolved Solids get too high, the following indicators or problems may occur;
Continual Addition of Excess Chemicals
Water Chemistry Tests Fine But Water is Not Clean and Sparkling (Water Has Odd Tint But You Can Still See Pool Bottom)
Algae Growth Despite a Good Chlorine Reading and Pool Water Chemistry
Varying and False Readings on Chemical Tests
The Saturation Index (SI), also known as the Langelier Saturation Index (LSI), is used to equate the calcium carbonate solubility of pool water and its effect on pool surfaces and equipment. Premature failure of equipment can occur with excessive corrosion. Clogging restrictions in pipes due to excessive scaling can result in reduced flows, increased back pressures, or reduced heater efficiency.
The formula is SI = pH + TF + CF + AF – 12.1, or, Saturation Index = pH + Temperature Factor (TF) + Calcium Hardness Factor (CF) + Total Alkalinity Factor (AF) minus 12.1. The 12.1 is a constant applied for Total Dissolved Solids between 0 and 1,000 ppm. When TDS is greater than 1,000 ppm, use the Table shown in Figure 11.3. The TF, CF and AF are factors based on the temperature, Total Alkalinity and Calcium Hardness levels in the water and are shown in Figure 11.4. The A result of between -0.3 and +0.5 indicates balanced water. The first step in properly balancing water is, knowing how to test the water. Once the test procedures are properly performed it is necessary to know how to read the data and treat the water accordingly. Tests for pH, alkalinity, water hardness, mineral content, and sanitizer levels must be performed on a regular basis. In order to combat the effects of bacteria, improper mineral levels, wrong pH levels, and poor sanitizer levels the person who is monitoring the pool water should know what treatment must be provided to correct the problems).
Figure 11.4 – Factor conversions for elevated TDS levels.
Use the reading closest to your actual reading in choosing the factor.
† Total alkalinity in this context refers to the total of carbonate and bicarbonate alkalinity. If cyanuric acid is used, a correction factor must be used (refer to local pool water specialist for the cyanuric acid correction factor).
Source: ANSI/APSP-11 2009
Figure 11.5 – Conversion factors for Temperature, Total Alkalinity and Calcium Hardness when using the Langelier Saturation Index (LSI).
For example: The Langelier Saturation Index of pool water (without cyanuric acid correction factor) with a pH of 7.6, a temperature of 81°F (TF), Total Alkalinity (AF) of 100, and Calcium Hardness (CF) of 400, and a TDS of 850 is calculated as SI = 7.6 + 0.7 + 2.0 + 2.2 – 12.1 = 0.4.
It should be noted that it is possible to have an ideal LSI and still have pool water that is corrosive or scaling. Each of the levels affecting pool water chemistry must be maintained within ideal ranges. For instance, an LSI which calculates as SI = 8.1 + 0.7 + 2.0 + 1.3 – 12.1 = 0.00 which states that the LSI is very good but the pH is high. In this state, the high pH can have a corrosive effect on cement based products if the calcium level is low.
Once water chemistry is balanced, it can be lost within 24 hours. Maintaining proper water balance requires constant monitoring, testing and chemical additions. Unfortunately, water chemistry balance is not as easy as adding one pound of treatment every other day; it requires knowledge, good record-keeping, patience, and dedication to keep the pool functioning properly and the users of the pool safe.
Mineral Balance – When discussing minerals in water chemistry the reference is usually to the presence of copper, iron, calcium, manganese, and magnesium, as well as various other minerals. Water is a solvent, in fact, it is often referred to as the universal solvent. As a solvent, when water chemistry is out of balance, water will dissolve any metallic material that it comes in contact with to satisfy its own needs for certain minerals and to achieve saturation point. After achieving saturation point, water will rid itself of any excess dissolved material (known as the precipitation point of water). In fact, water has the ability to dissolve, corrode, stain, scale, or calcify any surface in your pool in which the water comes in contact. This list of surfaces includes walls, floors, ladders, hand rails, light fixtures, internal pump and filter parts, grout, adhesives, and stone. The fact that water is volatile and must be kept under close supervision is critical to the long term performance of any pool system. The effects of improper mineral (metal) balance can also lead to colored water, stains and the formation of scale.
Measurement of pool chemicals and minerals utilize parts per million (PPM) as their reading, and pH is measured using the pH scale.
Figure 11.6 – Ideal PPM (parts per million) Readings for Successful Pool Water Chemistry (ANSI/APSP-112009).
11.4 Pool Water Chemistry and How It Affects Tile or Stone Installations
Maintaining pool water chemistry at proper levels is extremely important, not only to the owner and users of the pool, but also to the tile or stone installation or plaster located in the pool. Pool water which is out of balance can be unhealthy, unsightly, as well as time consuming and expensive to correct.
Correcting any problems with pool chemistry can actually take the pool out of use for a period of time until the proper balance is achieved to ensure the safety and well being of the pool users.
Tile and stone installations may also be affected by the pool chemistry. A big difference between correcting the pool water chemistry and fixing the tile or stone installation is how long the pool may be out of commission to make repairs. Let’s look at how pool water chemistry can cause problems with a tile or stone installation;
The pH of pool water should be between 7.2 and 7.8 on the pH scale. If the pH level gets too low then any cementitious material within the pool can be affected. Portland cement is reactive when exposed to acids and this exposure can have a deteriorating affect on the concrete or cement based product (e.g. grout, plaster, gunite). While the level of acidity is usually not very strong, there can be cumulative effects if the problem is not treated promptly or repeats over periods of time. If the pH of the pool is too low (acidic) the effects on the tile or stone installation can be;
Etched Cement Based Grout or Plaster
Cement Based Grout or Plaster Erosion
Blotchy Cement Based Grout or Plaster
Fading Cement Based Grout Color
Calcite Loss in Marble and Limestone (Loss of Stone Surface Material)
Calcium Loss in Portland Cement Based Installation Materials Which Can Lead to Weakening and Erosion of Materials
Stains on Horizontal Grout or Plaster
If the pH of the pool water gets too high (alkaline) the effects on the tile or stone installation can be;
Scale Formation on Pool Walls and Floor
Greater Potential for Algae Growth
If the Total Alkalinity and/or Total Hardness of the pool water get outside of their specific ranges there could be an effect on a tile or stone installation. If the Alkalinity or Hardness gets too low the effects on tile or stone can be;
Staining and Etching of Cement Based Grout or Plaster
Stains (in the Stone and/or Grout) Caused by Dissolving Metallic Components of the Pool
A problem resulting from Alkalinity and/or Total Hardness of the pool water being too high can lead to this effect on the tile or stone installations;
Scale formation on pool walls and floors
Pool water balance issues are very common in public pools and water features. The use of epoxy based grouts and setting material is a great choice to help overcome some of these potential issues. Epoxy materials are typically not affected by the etching or erosion problems inherent in cement based products by pH, alkalinity and hardness imbalance. LATICRETE recommends the use of LATICRETE® SpectraLOCK® PRO Grout† for all submerged pool, fountain, spa, or water feature installations. LATICRETE SpectraLOCK PRO Grout utilizes non-pigmented technology which means that the grout will not become blotchy or fade due to imbalanced pool water chemistry.
LATAPOXY® 300 Adhesive will provide the ultimate in adhesive performance in submerged installations. Providing incredible bond strength and high chemical resistance, LATAPOXY 300 Adhesive is the product of choice for installations in pools and spas with steel or fiberglass shells.
11.5 Tile Installation Maintenance and Repairs
It will be necessary, from time to time, to inspect the pool for possible problems with plumbing, lighting, fixtures, tile or stone, and fittings/connections. Improper water balance and exposure to chemicals can lead to potential problems with these installations so routine inspection is required. During some of these inspections, repairs and water balancing treatments it will be necessary to drain the pool.
Replacing tile, stone or grout should only be attempted when a pool is drained and sufficiently dry to accept a tile or stone installation. There should be no repairs or replacement attempted while submerged. To replace any tile, stone or grout in a pool, fountain, water feature or spa the use of any of the LATICRETE materials listed in Section 7 can be used for the particular substrate in question.
Proper maintenance of pool water chemistry will help to prevent problems and limit the down time of the swimming pool, fountain, spa, or water feature.
Unless otherwise noted, much of the information used in this section was excerpted from ANSI/APSP-11 2009, ANSI/NSPI-1 2003, and www.poolmanual.com.
1. Spring Pool Openings, Retrieved on September 24, 2008 from www.poolcenter.com.
2. Fall Pool Closings, Retrieved on September 24, 2008 from www.poolcenter.com.
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