Swimming Pool Water Problem Solving Guide

<BODY BGCOLOR="ffffaa" TEXT="0000ff" LINK="000aaa" ALINK="ff0000" VLINK="c000c0"> <A NAME=top></A> <CENTER><H1>Swimming Pool Water Problem Solving Guide</H1> <H3>For those with privately owned swimming pools using chlorine sanitisers</H3></CENTER><P> <STRONG>For an explanation of techical terms, follow the links or see <A HREF="tech.htm">A Layman's Guide to Technical Terms</A> or <A HREF="ph.htm">pH Explained</A>.<P> <STRONG>It can be difficult to make an accurate diagnosis for any particular swimming pool water problem. It is usually a case of considering several possibilities and selecting the most likely cause from other evidence, such as water tests. Browse through the various explanations for each symptom and see which you think is most likely to be responsible.<P> </STRONG> <UL> <LI><A HREF="#mark1">Water Quality Problems</A> <UL><LI><A HREF="#mark2">Cloudy, milky water</A> <LI><A HREF="#mark3">Green water</A> <LI><A HREF="#mark4">Rusty water</A></UL> <LI><A HREF="#mark5">Bather discomfort</A>, with sections on eye-sting, chlorine allergy.. <LI><A HREF="#mark6">Chlorination problems</A> <LI><A HREF="#mark7">Water balance problems</A>, with sections on pH, alkalinity.. <LI><A HREF="#mark8">Problems with pool surfaces</A> <LI><A HREF="#mark9">Filtration problems</A></UL><P><HR> <H3>WATER CLARITY PROBLEMS</H3><P> <A NAME=mark1></A> <A NAME=mark2></A> <STRONG>SYMPTOM: Cloudy/milky Water.</STRONG> There are four possible causes - your test kit will give you the best idea as to which is the most likely.<P> <UL><LI><STRONG>First possible cause:</STRONG><BR> Fine suspended particles floating in the water can lead to a milky white discolouration. This will probably be due to a precipitation of dissolved hardness salts as result of high <A HREF="tech.htm#ph1">pH</A> or <A HREF="tech.htm#talk">high total alkalinity</A>, or both. (Precipitation is a process where dissolved minerals become transformed into very small solid particles).</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Lower the pH or alkalinity using dry acid. To correct pH, add dry acid at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained.<BR>To correct alkalinity, the dose should be doubled. It is important to add the acid a little at a time and pre-dissolved at a dilution no stronger than 8:1. </UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Second possible cause:</STRONG><BR> Build up of dirt and bather pollution due to insufficient chlorine or poor filtration</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Backwash filter, then <A HREF="tech.htm#supercl">superchlorinate</A> by adding an unstabilised chlorine such as sodium hypochlorite or calcium hypochlorite to raise the <A HREF="tech.htm#hocl">free chlorine</A> to 10ppm.</LI> <LI>Add a clarifier to polish the water.</LI></UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Third possible cause:</STRONG><BR> The effectiveness of the chlorine has been reduced in pools using <A HREF="tech.htm#stabcl">stabilised chlorine donors</A> because the water is over-stabilised i.e. the levels of <A HREF="tech.htm#clstab">stabiliser</A> (cyanuric acid) are too high. This prolongs the time it takes to kill organisms (bugs) which can proliferate and lead to haziness in the water.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Replace some of the pool water by draining to waste (or carrying out an extra large backwash), then top up with fresh mains water. This will lower levels of stabiliser. <LI>Superchlorinate to 10ppm using the products recommended above.</UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Fourth possible cause:</STRONG><BR> The filter is blocked or is ineffective</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Check sand and replace if necessary. Your dealer should be called in if you do not feel equal to the task. <LI>Sand particles can become coated with calcium in some circumstances, especially in <A HREF="tech.htm#hh2o">hard water</A> areas. If the filter is not blocked and seems all in order in all other respects, treat with a filter cleanser to sharpen the sand.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark3></A> <STRONG>SYMPTOM: Cloudy/green Water.</STRONG> <UL><LI><STRONG>Probable cause:</STRONG><BR> At some stage, chlorine levels have fallen, or chlorine has become ineffective, allowing <A HREF="tech.htm#algae">algae</A> to colonise the water.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Shock dose with an unstabilised chlorine such as <A HREF="tech.htm#caocl2">calcium hypochlorite</A> or sodium hypochlorite, or use an algicide. Shock dosing usually produces the fastest results. For greenish discolourations (where the water is no more than tinted green), superchlorinate to 10ppm. For more serious problems, where the water is pea-soup green and the bottom is invisible, shock dose up to around 25ppm. This will kill the algae. <LI>Brush off any algae that may remain on pool surfaces. Look for colonies behind step ladders and around underwater lighting. <LI>Backwash the filter 24 hours later to remove dead algae from the top of the filter media. <LI>Any remaining haziness in the water should be removed by using a water clarifier. The cationic clarifiers are best in this situation. <LI>Thereafter maintain chlorine at around 3ppm to prevent a recurrence. <LI>If the pool is particularly susceptible to algae, consider regular use of an algicide or a chlorine with added algicide.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark4></A> <STRONG>SYMPTOM: Rust red Water.</STRONG> <UL><LI><STRONG>Probable cause:</STRONG><BR> Steel or ferrous metal fittings in the circulation system e.g. pipes are being corroded by low <A HREF="tech.htm#ph1">pH</A>. A shock dose of chlorine will then oxidise the ferrous particles creating rust. This can often happen after re-opening a pool.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>It is necessary to act very quickly to prevent consequential damage such as staining of the liner, if fitted. Contact your pool installer or pool dealer to see if it is safe to drain down and replace the water all in one go, or whether this should be done by progressive dilution. <LI>Remove any rust staining from the pool surfaces with a good tile and liner cleaner. <LI>Replace the ferrous metal fittings using pvc or copper. <LI>Ensure the fresh water is properly <A HREF="tech.htm#wbal">balanced</A> i.e. that pH and total alkalinity are within recommended parameters.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR><P> <A NAME=mark5></A> <H3>BATHER DISCOMFORT PROBLEMS</H3><P> <UL> <LI><A HREF="#mark51">Stinging eyes, sore throat and skin irritation</A> <LI><A HREF="#mark52">Blond or tinted hair turns green</A> <LI><A HREF="#mark53">Allergy to chlorine</A> </UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark51></A> <STRONG>SYMPTOM: Stinging eyes, sore throat and skin irritation.</STRONG> There are three possible causes - use your test kit to see which is the most probable.<P> <UL><LI><STRONG>First possible cause:</STRONG><BR> This could well be a <A HREF="tech.htm#ph1">pH</A> problem - the water could be too acidic or too alkaline. The pH of the human eye is around 7.4-7.5 - anything higher or lower will irritate. The problem would be made worse if the pH is out to the extent that it changes the species of chlorine (see pH explained)</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Correct the pH. To lower the pH, add dry acid at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained. To raise pH, dose at the same rate not with dry acid, but with soda ash.</UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Second possible cause:</STRONG><BR> High combined chlorine. <A HREF="tech.htm#comcl">Chloramines</A> are known to be an irritant. Note carefully the results you get on your DPD no3 test. Also, if you get an unpleasant chlorine smell, its odds on that the problem is due to high chloramines.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Break the chloramines down by <A HREF="tech.htm#supercl">superchlorinating</A> the pool with up to 10ppm free chlorine. <LI>Aim to allow no more than one third of the <A HREF="tech.htm#totcl">total chlorine</A> to be in the form of combined chlorine.</UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Third possible cause:</STRONG><BR> Some detergents used for cleaning pool sides and removing scum lines (tide-marks) are incompatible with chlorine. This can unfortunately include many products sold specifically for this application. The resulting reactions in the water can lead to eye and skin irritation. Similar reactions can occur if soaps or shampoos get into the water, for instance if bathers jump in to rinse off.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI><A HREF="tech.htm#supercl">Superchlorinate</A> to react-out the detergents. <LI>Change to cleaners that are chlorine compatible or abandon their use and resort to a little elbow grease.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark52></A> <STRONG>SYMPTOM: Blond or tinted hair turns green.</STRONG><P> <UL><LI><STRONG>Probable cause:</STRONG><BR> High levels of copper in the pool. This can arise either because of over-use of copper based algicides, or because the <A HREF="tech.htm#ph1">pH</A> of the pool water has been allowed to drop to a point at which it starts to corrode the copper fittings in the heater.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Correct the pH. To raise the pH, add soda ash at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained. <LI>Your pharmacist should be able to recommend a shampoo to remove the unwanted pigment (and dated punk image)</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark53></A> <STRONG>SYMPTOM: Allergy to chlorine.</STRONG><P> <UL><LI><STRONG>Possible explanations:</STRONG><BR> The most important thing is to make sure that you really are suffering from a genuine allergy and not something else. The discomfort you feel could be due to other factors. For instance, it be due to the fact that the <A HREF="tech.htm#ph1">pH</A> of the water is too low or too high. Alternatively it could be due to high levels of <A HREF="tech.htm#comcl">combined chlorine</A> (chloramines) - chloramines are known to be irritants. Both these things are explained in more detail in <A HREF="#mark51">'Stinging eyes, sore throat and skin irritation'</A> on this page). Test the water for pH and chloramines and correct as necessary.<P> Also, be your own guinea pig - use another pool sanitised with chlorine and see if you get the same reactions. If not, your problems are probably more to do with water treatment.<P> Bear in mind as well that chloramines are formed by the breakdown of nitrogenous compounds such as perspiration, cosmetics, mucous etc when <A HREF="tech.htm#hocl">hypochlorous acid</A> (free chlorine) reacts with them. The chloramines are eventually broken down by more hypochlorous acid to form harmless substances such as nitrogen gas. All this usually takes place in the pool water. However, the breakdown reactions can take place on the surface of the skin if for instance you have been working-out and sweating before swimming or using cosmetic preparations. Remove these nitrogenous compounds from your skin by taking a shower and washing thoroughly before entering the pool. The chances are you will find the pool water much more comfortable.<P> If neither of these suggestions help, then the likelihood is that you are one of the minority who experience an allergic reaction to chlorine. An allergy is defined as a hypersensitiveness to some foreign substance, small doses of which produce a violent and disproportionate reaction in the sufferer. Chlorine is unlikely to have been the original or primary allergen, but those suffering from allergies can unfortunately find themselves sensitised by chlorine</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>If you think you have a genuine allergy, then sadly the only remedy is to change to a non-chlorine sanitiser. Be warned that a number of these require to be dosed or shock dosed with chlorine. Consult your pool dealer for suitable alternatives.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR> <A NAME=mark6></A> <H3>PROBLEMS WITH CHLORINE LEVELS</H3><P> <UL> <LI><A HREF="#mark61">Inability to get a chlorine reading</A> <LI><A HREF="#mark62">Chlorine level difficult to maintain</A> </UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark61></A> <STRONG>SYMPTOM: Chlorine has been added to the water, but there is no reading on the test kit.</STRONG><P> <UL><LI><STRONG>Probable cause:</STRONG><BR> The chlorine level in the pool is so high that it bleaches the colouring agent in the test tablet. To confirm the diagnosis, see if you can detect a smell of chlorine off the surface of the water, or repeat the DPD no 1 test with only a droplet of pool water in the test tube and watch closely to see if there is a red discolouration before the bleaching occurs.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Determine the approximate level of chlorine by diluting the sample of pool water with an equal quantity of natural or distilled water; multiply the answer by 2. If there is still no reading, repeat the process and multiply the answer by 4...and so on. <LI>If the actual chlorine reading is not too high (i.e. around 10ppm), suspend dosing and allow it to drop over a period of time. <LI>If the chlorine reading is significantly higher, or if you need to use the pool in the near future, add sodium thiosulphate to reduce the free chlorine. <STRONG>WARNING</STRONG> The recommended dose rate is 0.5kg per 100 cu metres (22,000 galls). Apply this in several much smaller additions, testing after each dose. An overdose of thiosulphate can leave you with 'negative chlorine' i.e. a chlorine deficit for a considerable time.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark62></A> <STRONG>SYMPTOM: The chlorine level is difficult to maintain.</STRONG> There are three possible causes.<P> <UL><LI><STRONG>First possible cause:</STRONG><BR> In outdoor pools, the <A HREF="tech.htm#hocl">hypochlorous acid</A> (free chlorine) is being decomposed by ultra violet from the sun's rays</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>For pools using liquid chlorine (sodium hypochlorite) or calcium hypochlorite, add <A HREF="tech.htm#clstab">stabiliser</A> (cyanuric acid) at a rate of 3kg per 100 cu metres (22,000 galls). This should be dosed directly into the pool, NOT pre-mixed with the chlorine. <LI>Alternatively, switch to a stabilised chlorine - <A HREF="tech.htm#dichl">dichlor granules</A> or <A HREF="tech.htm#trichl">trichlor tablets</A></UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Second possible cause:</STRONG><BR> High water temperature. The logic is simple. Bugs are more at home in warm water and breed more quickly. The greater number of bugs will create a higher <A HREF="tech.htm#cldem">chlorine demand</A>.<BR> As a rough rule of thumb to bear in mind if there is a heat wave, if the pool water temperature goes above 80 degrees farenheit, the chlorine demand will double for each increment of 10 degrees.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>The dose rate of chlorine must be increased proportionately. Keep a close check on chlorine levels in hot weather.</UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Third possible cause:</STRONG><BR> Because chlorine levels have not been high enough, there has been a build-up of pollutants, and therefore an increase in chlorine demand.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI><A HREF="tech.htm#supercl">Superchlorinate</A> the pool to around 10ppm free chlorine</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR> <A NAME=mark7></A> <H3><A HREF="tech.htm#wbal">WATER BALANCE</A> PROBLEMS</H3><P> <UL> <LI><A HREF="#mark71">Tendency for the pH to remain low</A> <LI><A HREF="#mark72">Tendency for the pH to be permanently high</A> <LI><A HREF="#mark73">pH values are erratic and fluctuate</A> <LI><A HREF="#mark74">pH is locked</A> <LI><A HREF="#mark75">Tendency for the alkalinity to be too low</A> </UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark71></A> <STRONG>SYMPTOM: Tendency for the <A HREF="tech.htm#ph1">pH</A> to remain low (below 7.2).</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> This is usually due either to low pH of mains water (especially in soft water areas) or to the use of acidic <A HREF="tech.htm#cldon">chlorine donors</A>, such as <A HREF="tech.htm#trichl">trichlor</A></LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Correct the pH. To raise the pH, add soda ash at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained. <LI>Consider changing to a high pH chlorine source to help achieve a natural balance between the low pH of the water and the high pH of the chlorine donor. <A HREF="tech.htm#dichl">Dichlor</A> is roughly pH neutral; <A HREF="tech.htm#caocl2">calcium hypochlorite</A> and sodium hypochlorite are high pH chlorine donors.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark72></A> <STRONG>SYMPTOM: Tendency for the pH to be permanently high (above 7.6).</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> This is due to either (1) high pH of mains water (especially in <A HREF="tech.htm#hh2o">hard water</A> areas) or (2) to the use of alkaline chlorine donors such as calcium or sodium hypochlorite, or (3) to hardness salts being leached from new concrete or mosaic pools.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>The remedy is the same irrespective of which factor is at work here - correct the pH. To lower the pH, add dry acid at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained. <LI>For (1) and (2), consider changing to a low pH chlorine source to help achieve a natural balance between the high pH of the water and the low pH of the chlorine donor. <A HREF="tech.htm#trichl">Trichlor</A> is the obvious chlorine donor to choose. For (3), the difficulties with new concrete pools will clear up of their own accord given sufficient time. </UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark73></A> <STRONG>SYMPTOM: pH values are erratic and fluctuate.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> The reason will be that the <A HREF="tech.htm#talk">total alkalinity</A> will be too low to buffer the pH</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Add sodium bicarbonate to ensure the total alkalinity remains above 100ppm. The dose rate is 3kg per 100 cu metres (22,000 galls) of pool water.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark74></A> <STRONG>SYMPTOM: <A HREF="tech.htm#ph1">pH</A> is locked.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> The water is over buffered due to <A HREF="tech.htm#talk">high alkalinity</A>. This is a not uncommon problem in <A HREF="tech.htm#hh2o">hard water</A> areas where the mains feed water has a high total alkalinity.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Add dry acid to lower the total alkalinity to below 200ppm. The dose rate is 2kg per 100 cu metres (22,000 galls) of pool water. It is important to add the acid a little at a time and pre-dissolved at a dilution no stronger than 8:1.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark75></A> <STRONG>SYMPTOM: Tendency for the alkalinity to be too low.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> The local feed water is low in bicarbonates so that whenever the pool is topped up from the mains, it dilutes the bicarbonates in the pool. This is a particular problem in <A HREF="tech.htm#sh2o">soft water</A> areas.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Add sodium bicarbonate to raise the total alkalinity to around 100ppm. The dose rate is 3kg per 100 cu metres (22,000 galls) of pool water (this should raise the level by 20ppm per dose).</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR> <A NAME=mark8></A> <H3>PROBLEMS WITH POOL SURFACES</H3><P> <UL> <LI><A HREF="#mark81">Loss of grouting in mosaic/tiled pools, or sharp edges</A> <LI><A HREF="#mark82">Pool surfaces feel rough and scaly</A> <LI><A HREF="#mark83">Pool surfaces feel slippery</A> <LI><A HREF="#mark84">Tide mark on pool wall at water line</A> </UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark81></A> <STRONG>SYMPTOM: Loss of grouting in mosaic/tiled pools, or sharp edges around tiles.</STRONG> There are two possible factors at work here:<P> <UL><LI><STRONG>First possible cause:</STRONG><BR> In <A HREF="tech.htm#sh2o">soft water</A> areas, the grouting is being etched by the pool water. This is because there is insufficient calcium in the water. There is a tendency for water to form an equilibrium by searching for calcium - in this case from the grouting or plaster substrate. </LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Regrout the pool and increase calcium levels in the water by adding calcium chloride flakes so as to achieve a minimum <A HREF="tech.htm#calh">calcium hardness</A> level of 250ppm. Alternatively, use <A HREF="tech.htm#caocl2">calcium hypochlorite</A> for shock dosing or for regular sanitisation - calcium will be automatically added to the water in using this sanitiser.</UL></UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <UL><LI><STRONG>Second possible cause:</STRONG><BR> High levels of sulphate in the water. You will need to get your pool centre to test for sulphates to confirm this diagnosis. The sulphate level shoul not exceed 350ppm.<BR> High sulphates are caused by (a) high sulphates in the mains water (b) the frequent use of dry acid (sodium bi<EM>sulphate</EM>) or (c) use of aluminium <EM>sulphate</EM> as a water clarifier.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>If you suspect factors (b) or (c), dilute with fresh water and switch to alternative methods of lowering the <A HREF="tech.htm#ph1">pH</A> (e.g.using <A HREF="tech.htm#trichl">trichlor</A> as the main pool sanitiser), or clarifying the water (a sulphate-free treatment). There is not much you can do about (a).</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark82></A> <STRONG>SYMPTOM: Pool surfaces feel rough and scaly.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> The <A HREF="tech.htm#wbal">balance</A> between pH, total alkalinity and calcium hardness is incorrect, and the water is technically 'scale forming'.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Test for pH, total alkalinity and calcium hardness and bring them within recommended parameters. It is best to carry out a 'Langelier' water balance calculation (see water balance), or ask your pool centre to do this for you.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark83></A> <STRONG>SYMPTOM: Pool surfaces feel slippery.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> This is probably <A HREF="tech.htm#algae">algae</A> forming a colony on the pool surface due to insufficient chlorination at some stage, or to a 'dead spot' in the water circulation.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Sweep the affected areas vigorously to remove as much algae as possible, then shock dose with an unstabilised chlorine (follow the procedure set out for <A HREF="#mark3">killing algae</A>). Prevent a recurrence by periodic use of an algicide</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark84></A> <STRONG>SYMPTOM: Tide mark on pool wall at water line.</STRONG><P> <UL><LI><STRONG>Likely cause:</STRONG><BR> What you are seeing is a build up of greasy deposits such as cosmetics, sun cream or body fats.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Clean with a tile and liner cleaner ensuring that it does not contain detergent compounds that could react with chlorine and cause bather discomfort.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR> <A NAME=mark9></A> <H3>FILTRATION PROBLEMS</H3><P> <UL> <LI><A HREF="#mark91">Ineffective filtration in sand filters</A> <LI><A HREF="#mark92">Ineffective filtration in cartridge filters</A> </UL><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark91></A> <STRONG>SYMPTOM: Ineffective filtration in sand filters.</STRONG><P> <UL><LI><STRONG>Possible causes:</STRONG><BR> Either (a) sand has escaped from the filter leaving insufficient filter media to take out suspended particles, or (b) the filter is blocked by accumulated debris or (c) the sand particles are coated in calcium.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>For (a), its simply a matter of topping up the sand. If (b), the filter is blocked by debris, backwash. If the problem is persistent, and the sand particles are becoming coated with calcium (more likely in a <A HREF="tech.htm#hh2o">hard water</A> area), use a filter cleanser.</UL></UL><P> <FONT SIZE=-1> <CENTER> <A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm" TARGET="_parent">[Back to Home Page]</A><P></CENTER></FONT><P> <HR SIZE="4" WIDTH="200" ALIGN="CENTER"><P> <A NAME=mark92></A> <STRONG>SYMPTOM: Ineffective filtration in cartridge filters.</STRONG><P> <UL><LI><STRONG>Possible causes:</STRONG><BR> Either the cartridge is in poor condition, allowing particles to pass through it or the demands on it from debris in the water are too great for it to cope.</LI><P> <STRONG>To Remedy:</STRONG> <UL><LI>Replacing the cartridge is the obvious remedy. If the problem is persistent, try using a filter aid or water clarifier. Failing this, the ultimate remedy is to install a sand filter.</UL></UL><P> <P> <CENTER><FONT SIZE=1>&copy Copyright remains with the author. All rights reserved. See <A HREF="cright.htm">conditions of copyright</A></FONT></STRONG><P> <HR><P><FONT SIZE=2><STRONG><A HREF="#top">[Back to top of document]</A> <A HREF="pools.htm">[Back to Home Page]</A> <HR> Pool Owners Guide: </STRONG><A HREF="poolcare.htm">[Basic poolcare]</A> <A HREF="dosing.htm">[Dosing strategies]</A> <A HREF="tips.htm">[Topical tips]</A><BR> <STRONG>Technical Section: </STRONG><A HREF="tech.htm">[Technical terms defined]</A> <A HREF="ph.htm">[pH explained]</A> <A HREF="water.htm">[Balanced water test]</A> <A HREF="bestbuys.htm">[Recommended products]</A><BR> <STRONG>Buy Your Own Pool: </STRONG><A HREF="why.htm">[The reasons people do]</A> <A HREF="newpool.htm">[The choices, the costs]</A> </FONT SIZE></CENTER> <HR> </BODY>