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ContentsContents............................... 2

Introduction..........................3

Spa Health & SafetyGuidance .............................4

Why do we test thewater? .................................5

Parameter Testing ........6

Disinfectant..........................6

Bromine..................................7

Chlorine – Free andTotal ........................................ 8

Ozone ....................................9

pH............................................. 9

Total Alkalinity ..............10

Cyanuric Acid ................. 10

Calcium Hardness.......... 11

Phosphate ........................11

Dissolved solids............... 12

Turbidity............................... 13

Water balance ............... 14

Microbiological testing 15

How often should I betesting? ..............................16

Test Method Selection .17

Choosing a Sample ..... 21

Best Practice for WaterTesting ...............................22

Hints and Tips to Testingwith Photometers..........23

Spa Troubleshooting ..25

A little about Palintest27

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IntroductionThisPalintest Spa Chemistry booklet will go over allthe necessary parameters that you may wish to testfor, the frequency of testing, and the multiple testingmethods available to you.

We always recommend that you seekadvice onyour local authority legislation.

The Engineers’ Edition is more extensive anddetailed covering all Pool & Spa parameters. Pleasecontact Palintest at sales@palintest.comfor moreinformation.

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Spa Health & Safety GuidanceSpas tend to have a higher ratio of bathers to watervolume in comparison to swimming pools. Thisincreases the riskof contracting diseases from thewater. The highest risk is from spas that are eitherpoorly designed or not well maintained. Key advicefor a healthy spa is;

• Bather numbers should not exceed thenumber of seats or stated bather load.

• In commercial settings, specifically holidaylets, the hot tub should be completelydrained, cleaned, refilled and disinfectedweekly or after each rental.

• When refilling a hot tub, sufficienthypochlorite should be added to keep thechlorine residual at 5.0 mg/L.

• Regular cleaning and replacement ofcartridge filters where applicable.

• During commissioning,or after a hot tub hasbeen left empty or unused, it should be shockdosed with chlorineat 50 mg/ L for 1hour,with the pH maintained between 7.0-7.4,andthen fully drained.

• Follow a suitable water treatmentprogramme.

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Why do we test the water?Every user of the spa has a right to feel safe andcomfortable whilst bathing. Thisdoesn’t just meanthe physical safety and comfort, but the watershould also be tested to make sure it is suitable forpeople to bathe in.There are four main reasons forwater testing:

• Bather safety and comfort• Removal of contamination• Care of plant and pool surrounds• Control of chemicals used

Failure to test the water correctly can easily lead tobather illness,irritation or problems with the spa, soa regular testing procedure should be drawn up andfollowed.

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Parameter TestingThe number of parameters tested in a spa or hottub tends to be less than that found in a pool.However, as spas tend to be a smaller pool ofwater, it is important that you follow a correcttesting regime.

DisinfectantNormally bromine is used to disinfect spa water asit’s more effective at higher temperatures. However,both bromine and chlorine can be used to keep itfree of harmful bacteria.

Whichever disinfectant you are using, the levelsshould be tested regularly as outlined in the normaloperating procedure (NOP).National legislation willdetermine frequency of testing required. Rememberthe more testing you carry out, the safer and betterrun the pool is.

All advice given in this booklet is generalisedinformation, and you should always checkyour locallegislation and guidelines.

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BromineGenerally,bromine is used to treat hot tubs andspas and chlorine is used for the treatment of pools,although there is much cross-over. Bromine ismoreactive at higher pH levelsand more stable andeffective at higher temperatures than chlorine. Forthose with sensitive skin,bromine can be preferableas it does not cause as much skinand eye irritationas chlorine.

Recommended bromine levels in the UKfor pools andspas are 4.0–6.0 mg/L with shockdose of 10 mg/L,although this can vary if additional chemicals such assodium hypochlorite are also added to the water.

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Chlorine– Free and TotalIt is important to monitor both the free and totalchlorine levels.When chlorine reacts with nitrogencontaining molecules in the water, they formcombined chlorines.Although combined chlorinesstill have disinfection properties, they are not asefficient as free chlorine.

In the UK,if chlorine is being used in a well- designedpool you should be looking for a free chlorineresidual of 3.0- 5.0 mg/L. The combined chlorine (ameasure of unwelcome disinfection by- products)should be as low as possible and certainly less thanhalf the free and never more than 1mg/L. The exactrequirements for your spa may vary, and will bestated in your NOP.

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OzoneOzonecan purify water 3000 times faster thanchlorine. It is also very effective at killingCryptosporidium and Giardiawhich are unaffectedby chlorine disinfection.

Ozone use does not affect the pH level of the spa. Itdoes have a large initial cost, but when using ozone,the free chlorine levelscan be much lower (0.5 mg/Lfor a pool,and 2–3 mg/L in spas and hydrotherapypools).

pHThe pH is a measure of how acidic or alkaline thewater is,and can affect how other spa chemicalswork, as well as bather comfort and lifetime of spafittings. The heating of the spa water will increasethepH.

Ideally you are looking for a pH of 7.2–7.4as thisallows effective disinfection but is also comfortablefor the bather. An overall range of 7.0–7.6 isacceptable in most spas. pH should always bemeasured at the same time as the disinfectant.

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Total AlkalinityAlkalinityprotects the water from dramatic changesin pH when the pool is in use.

Total alkalinity should be measured at least once aweek and the levels should be in the range 80–200mg/L CaCO3. Levelsbelow 80 mg/L could make thepH unstable whereas above 200 mg/L the pH couldbecome difficult to change.

Cyanuric AcidCyanuric acid is commonly referred to as a chlorinestabilizerand can be used on outdoor spas.Withoutcyanuric acid present, chlorine is more quicklydegraded by UV light.

Levelsshould be below 200 mg/L, with manyauthorities suggesting levelsbetween 25 and 50mg/L are ideal.

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Calcium HardnessIf calcium levels in the water are low, spa surroundsor grout can be eroded by the water. Likewise,ifthereis too much calcium, deposits will start dropping (asin a kettle) and can leave ‘hard water’ marks. Calciumhardness should be measured once a week, and alevelbetween 80–200 mg/L maintained.

PhosphatePhosphate is naturally present in water andpromotes the growth of algae.Control ofphosphates is especially important for outdoor spas.The level of total phosphates in the spa watershould be 0.01mg/L or below.

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Dissolved solidsMains water is likely to have several hundred mg/Ltotal dissolved solids (TDS). Spa chemicals andpollution will increase this - so high TDS is a warningthat the spa water quality is decreasing. It should notbe allowed to risemore than 1,000mg/L above thatof the mains water - up to a maximum of 3,000mg/L. Measure it weekly with an electronic meter: ifit's too high, dilute.

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TurbidityThe turbidity of the water is a measure of howcloudy the water is.Thishas recently become morefrequently tested in pools. In spas the testing of theturbidity ismore difficult due to the bubbles, but thiscan be tested once the air jets are off and the waterhas settled.

Traditionally it has been that if you can see thebottom of the pool at the deep end then the clarityis sufficient. However, recent recommendationsstate that pool water should be measured, and thelevel of turbidity should be 0.5 NTU(NephelometricTurbidity Units) or less.This level is below that whichthe human eye can see,and so a meter specificallydesigned for turbidity measurement should be usedto test the water weekly.

Checking the turbidity also can indicate otherproblems such as:

• Poor water chemistry• Deteriorating filter quality• Inadequate backwashing routine• Incorrect flow rate or pipe sizing

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Water balanceWater balance describes how likelythe water is toscale or corrode its surroundings and is importantwhen considering the lifetime of your fixtures andfittings. If the water will dissolveminerals around it,then it is described as corrosive. If the water willtend to deposit minerals it is considered scaling.

The most commonly used Water Balance index forspas is the Langelier Saturation Index.The RyznarStability Index is an alternative scale to use.

In order to calculate the Water Balance, you mustcombine measurements of the pH, calciumhardness, total alkalinity, temperature, and TDSofthe water. The resulting value from the WaterBalance Calculation will give you an indication ofwhether the water needs the balance addressing.

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Microbiological testingMicrobiological testing is checking there are nodangerous pathogens which can cause bathersserious illnesspresent in the water.

Regularly you need to take a water sample for threetests of microbiologicalwater quality - colonycounts, coliforms and E. coli. (also test this if the poolhas been shut down).

Your local authority may request this is done by anaccredited laboratory, or alternatively you can carryout an on- site test using ColitagTM or Nutridisks.

These are the results you need to be reassuredeverything is safe for bathing.

Colony Count Not more than 10CFUper100mL

Total Coliforms Absent in 100 mL

E. coli. Absent in 100 mL

Ps.Aeruginosa Absent in 100 mL

Legionella Absent in 100 mL

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How often should I be testing?Thiswill be stipulated by your local authority, andwill depend on the amount the spa is used, but as ageneral rule;

Daily• Disinfectant Residual

(Chlorine, Bromine, Ozone etc.)• pH• Total Dissolved Solids

Weekly• Alkalinity• Calcium Hardness• Cyanuric Acid• Water Balance

Monthly

• Turbidity• Microbiological

(Legionellaquarterly)

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Test Method SelectionWhen testing parameters in pools there are anumber of options in terms of the test method. Thetype most suitable to you will depend on costs andpool usage.

Test StripsTest strips are the simplest and mosteconomical form of testing and althoughcommon in the domestic pool market,should be viewed as producing resultsthat are indicative only.

Colorimetric MethodsColorimetric techniquesinvolve the addition ofreagents to water samples,producing a colour changewhich is proportional to theconcentration of theparameter under test.

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Comparator Visual SystemsComparator discs and block systems are utilisedthroughout the industry and are manufacturedagainst verified colour standards, therefore aresuitable for reporting purposes. They are a step upfrom test strips in terms of accuracy, whilst stillbeing relatively low cost and easy to use. However,these systems can have wide incremental resultsteps, involve a degree of interpretation and areprone to variations in colour perception by thehuman eye.

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PhotometersThe use of photometers removes the humanelement from the result reading process by digitallyanalysing test colours, referring to calibration datastored within the instrument. Although more costlythan visual techniques,photometric instruments aremore accurate and reliable. In addition, test resultscan be stored by instruments, then downloaded tocomputer- based databases via cable or Bluetooth.This is particularly useful for auditing purposes.

A photometer works by measuring the amount oflight that passes through the sample and opticalfilter and hits the detector. The darker the samplecolour, the less light will pass through it.

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Electrochemical MethodsElectrochemical techniques, such as metersfor measuring pH, TDS,and conductivity,are employed within the pool market but toa much lesserextent than colorimetrictechniques. TDSand conductivity can onlybe measured electrochemicallyand notusing colorimetry.

Well maintained electrochemicalmeters arehighly accurate and not influenced by manyof the interfering factors seen withcolorimetric measurement of someparameters.

TurbidityOnly instrument- based techniques are suitable dueto the recommended levelsof turbidity being belowthe capability of the human eye. Specialist turbiditymeters can quicklyprovide assurance that the poolturbidity is below 0.5 NTU.

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Choosing a SampleWhen testing the key parameters of a pool and spa,getting the sample is key.

Many modern spas have multiple outlets and inletsacross the pool, and so samples should be taken atvarious parts of the pool at a depth of 100–300mm.

These locations should become the routine samplingpoints, and together will give an overall view of thepool water quality.

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Best Practice for Water Testing1. Testing equipment should be kept clean, with no

water marks, fingerprints, scratches or stainsand preferably, rinsed with distilledwater whereapplicable. Note that plasticware candeteriorate over relatively short periods of timeand should be replaced regularly

2. Test methods must be followed carefully as perinstructions.

3. Reagent tablets must be fully dissolved beforeyou try to read the result.

4. Ensure that test reagents are within the bestbefore date.

5. Do not mix and match reagents and test kitsfrom different manufacturers

6. If deposits or bubbles form, leave for a fewminutes to clear unless the test is time specific.Bubbles can usually be cleared using a crushingrod or by tapping the side of the test tubegently.

7. For results that are above the range of the test,use the dilution method and test again.

8. Analytical instruments should be servicedannually.

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Hints and Tips to Testing withPhotometers

1. To prolong the lifetime of your instrument and getthe best performance, you should have fullcalibration checks each year. Checkstandards canhelp you quicklysee if your instrument is withinspecification.

2. Always follow the test procedure carefully, makingsure you add the reagents in the right order andstick to the recommended standing times andtemperature conditions.

3. Test tubes must be kept in a clean condition.Always wash and dry them thoroughly after use.Dirty tubes may be soaked in a weakdetergent solution but must be carefullyrinsed after. Any tube that is scratched orstained must be replaced.

4. Caps and crushing rods should be cleanedimmediately after use and discarded if theybecome stained.

5. When measuring the sample volumerequired, make sure that the lowest point ofthe meniscus in exactly on the fill line (seediagram).

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6. The blank is a test tube filled with the samplewater, but no reagents. The photometer uses thisas a background to compare to your test samplecolour.

7. Do not touch the tablet reagents whentransferring them to the test tube as it willcontaminate them, and you will not get accurateresults.

8. Ensure you fully crush the tablet. After thestanding period, do not shake or invert the testtube. Some tests form fine particles which sinktothe bottom and will not influence the test.

9. If bubbles adhere to the sides of the tube, rubthem away gently using the crushing rod.

10.Always use the light cap on your photometer toget accurate results.

11. Never shake the tube to mix thecontents, always stir it with acrushing rod.

12. The results for these tests aregiven in a number of differentunits, always quote the unitswhen reporting your data, andcheck all data is expressed in thesame units when making comparisons.

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Spa TroubleshootingIssue Possible

CausePossible

Solution

pH notwithin limits

pH <7.0 – toomuch acid

pH >7.6 – notenough acid

Adjust the pH by using pHplus or pH minus to eitherlower or raise the Ph levels.Recheck the pH after 15mins.Repeat until within limits.

Disinfectantnot withinlimits

Chlorine:

<2 mg/L or

>5 mg/ L

Bromine:

<2 mg/L or

>6 mg/ L

If levels below recommendedlimits close the spa and adddisinfectant, retest until withinrecommended limits.

If above recommended limitspartially drain the hot tub andreplace with sourcewater,and retest till within respectedlimits.

Cloudy hottub water

Spa not beenin use

Checkover the hot tub foreverything functioning, andreview control strategies.

Circulationpump failure

Restart the pump, and ensureboth pH and disinfectionlevels are within limits

Lowdisinfectionlevels

With lower levelsofdisinfection,microbial growthis likely.Shock dose the spa to50 mg/ L for 1hour. Empty,

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Cloudy hottub water

clean and disinfect, bringingthe spa back into correctoperation.

Incorrectdosing ofchemicals

Chemicals should becompletely dissolvedbeforebeing added to the spa.

Filter cleaning Filters require to be rinsedfollowing backwashing,enabling the dirt to bedischarged.

Algal/ bacterialgrowth

Raise disinfection to 10mg/Land leave overnight. Removeany algal deposits byscrubbing, then returndisinfection to normaloperating levels.

High batherload

Filter not capable to cope withhigh bather loads, clean filterand replacewater.

Presence offoam

Remove water, and refill.Discontinue using cleaningproducts with detergents.

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A little about PalintestAt Palintest we make water analysis technologieswhich help to safeguard consumers around theworld each day. A critical part of the leisure industry,our technologiesensure that we can all bathe andplay safely.

Our company name comesfrom one of the pioneers ofour business,Dr Tom Palin.

Dr Palin was instrumental inthe development of standardDPDmethods for measuringchlorine levels in water. A keyfigure across the industry, DrPalin worked at Palintest,developing chemicalreagents in the form oftablets for measuringdifferent parameters of water quality. Sincethen wehave been continuing his legacy by making watertesting simple and accessible for everyone, officiallychanging our name to Palintest in 1989 to honourDr Palin’s work.

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