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The Swimming Pool Operators

and Owners Resources Pages

Resources Page 6 - Common Pool Problems

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ITEMS ON THIS PAGE:-

  • MY POOL HAS A HIGH CHLORINE LEVEL - AND THE WATER IS STILL GREEN.

  • I'M SURE THERE IS CHLORINE IN MY POOL - THE WATER IS CRYSTAL CLEAR, BUT MY TEST KIT SHOWS THERE IS NO CHLORINE PRESENT.

  • WE HAVE A LOT OF COMPLAINTS ABOUT SORE EYES, AND THE SMELL OF CHLORINE. EVERYBODY SAYS WE HAVE TOO MUCH CHLORINE IN THE WATER. WE HAVE CHECKED THE LEVEL OF FREE CHLORINE, AND IT IS CERTAINLY NO MORE THAN 1.5 PPM.

  • I THINK MY POOL MAY BE LEAKING!!

(1) - MY POOL HAS A HIGH CHLORINE LEVEL - AND THE WATER IS STILL GREEN.

This is a very common problem which occurs when Stabilized Chlorine Granules are used. These contain a stabilizer, - Cyanuric Acid, - which reduces the destruction of chlorine by Ultra Violet light from the sun.

Although the Chlorine will be consumed, the Cyanuric acid will remain in the water, and every time that the pool is dosed with stabilized chlorine granules, the Cyanuric Acid level will increase.

The optimum level for Cyanuric Acid in swimming pool water is about 25 - 30 ppm. If the level is below that figure, more chlorine will be destroyed by sunlight than is necessary. BUT, - if the Cyanuric acid level increases above about 30 ppm, the chlorine becomes progressively OVERstabilized, and its power of oxidation and disinfection is steadily reduced. Once the level exceeds 50 ppm the disinfection rate usually begins to noticibly fall.

This leads to a situation known as "Chlorine Lock". - Substantial levels of chlorine are present in the water, and are indicated on a test kit. But this Chlorine is "Locked up" by the high levels of Cyanuric Acid, and is unable to work normally.

Cyanuric Acid levels in pool water can only be controlled by dilution - ie, draining of some water and refilling with fresh. The best way to achieve this is during the weekly backwash cycle, by simply extending the backwash time, and then topping up with fresh water.

If a pool is in regular use, it is probable that about 5%, - or even more, of the pool volume has to be replaced each week in order to maintain the Cyanuric Acid content at an acceptable level.

It is a very good idea for pool owners to get a Cyanuric Acid test kit, - they are not expensive, - and monitor the levels each week. If the levels continue to rise, the backwash times can be extended until a stable level is maintained.

If the Cyanuric Acid level is above 50 ppm, and below 100 ppm - it is usually sufficient, to drain off about half the pool volume, and refill with fresh water. If the level is over 100 ppm it is a good idea to completely drain and refill the pool. Check with you pool Builder first, that emptying the pool will not cause any complications.

Trichlor chlorine tablets also contain Cyanuric Acid, though nowhere near as much as in the Stabilized Chlorine granules. Even so, it is still a good idea to monitor the levels of Cyanuric Acid in the pool water.

  • - - - - - - - - - - ( Also see "Cyanuric Acid" on Resource Page 4 ) - - - - - - - - -

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(2) - I'M SURE THERE IS CHLORINE IN MY POOL - THE WATER IS CRYSTAL CLEAR, BUT MY TEST KIT SHOWS THERE IS NO CHLORINE PRESENT.

Chlorine has a bleaching effect, and high levels create a very strong bleach which can destroy any colours produced by test kit reagents.

The initial symptoms may be that the Chlorine level appears to be falling rapidly, or that the addition of Chlorine does not cause an increased level to be indicated by the test kit.

To check for high levels of Chlorine, it is necessary to accurately dilute a pool water sample with NON-Chlorinated water. Distilled or De-ionised water is ideal, but in practise, bottled water, or even boiled water will give a reasonable indication.

Most commercial test kits will provide the means for accurately diluting a sample of water. Otherwise use a clean jug and carefully add ONE measure of pool water and FOUR measures of non-chlorinated water. Mix thoroughly, and then take a sample from this solution in the usual way, and test for Chlorine. Multiply the result seen, by FIVE.

It is always a good idea to confirm your test, so create a fresh sample again, but this time using ONE measure of pool water to NINE measures of non-chlorinated water. Now multiply the result by TEN. This answer should give a similar result to the first test. If not, increase the Dilution of the sample until consistant results are obtained. Dilution rates of 25 to 1 are not uncommon when pools have been heavily over chlorinated!

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(3) - WE HAVE A LOT OF COMPLAINTS ABOUT SORE EYES, AND THE SMELL OF CHLORINE. EVERYBODY SAYS WE HAVE TOO MUCH CHLORINE IN THE WATER. WE HAVE CHECKED THE LEVEL OF FREE CHLORINE, AND IT IS CERTAINLY NO MORE THAN 1.5 PPM.

This is another common problem, especially in commercial pools. When Chlorine combines with organic debris - such as is found in pool water, provided there is ENOUGH Chlorine, this organic material is OXIDIZED into nitrogen gas and chloride salts. Nitrogen gas is tasteless, colourless, and odourless, and high levels of chlorides just give a salty taste to the water.

However, if there is NOT enough Chlorine, or high levels of organic material are present, the normal oxidation process does not work correctly. Instead of rapidly oxidizing the organic material to harmless by-products, the oxidation process is "swamped" by the high level of organics, and the oxidation process slows down, and starts producing compounds of Chlorine combined with the organic material.

Instead of Nitrogen gas and Chloride salts being produced, Nitrogen Trichloride gas is produced. Nitrogen Trichloride is a type of Tear Gas, and causes the familiar sore eyes. It is a pungent gas which produces that familiar, harsh, "Swimming Bath Smell" which is often mistakenly confused with Chlorine.

It is not sufficient to simply test for Free Chlorine, especially at a commercial, or heavily used pool. The level of Combined Chlorine Compounds, known generally as Chloramines, must also be checked. The Maximum acceptable level of Chloramines is 1 ppm. A correctly operated commercial pool should be able to maintain a Chloramine level of 0.5 ppm or less

High levels of Chloramines will "soak up" free Chlorine residuals very quickly, casing the situation to worsen, and increase overall chemical consumption.

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(4) - I THINK MY POOL MAY BE LEAKING!!

Well, yes!, this sometimes happens, but there is quite a lot you can do to check it out. The most common place for water leaks is from the Multiport Valve gasket. check the backwash pipeline for a trickle of water while the circulation system is running. Undo the socket union that connects the backwash pipe to the multiport, or undo the little screw-in sight glass jar, or simply check the far end of the pipe where it meets the drains. Even a steady drip-drip-drip from a worn out spider gasket inside the valve can cause a considerable loss of water over 24 hours.

The next test is to make sure that the water is not not simply evaporating. Take a large plastic bucket and threequarters fill it with pool water. Now, float it in the pool, and tie it to the handrail or something similar that will prevent it from tipping over and spilling. Make a mark on the INSIDE of the bucket on the inside waterline, and also make a mark on the pool shell at the pool waterline. Leave the pool unused for a day or two, and then check both water levels. If they BOTH have gone down by the same amount - the loss is simply due to evaporation. But, if the pool level has gone down MORE than that in the bucket - then you do have a leak.This method works for both indoor and outdoor pools, and it doesn't matter if it rains or not.

Assuming you now believe you do have a leak, some further tests are needed. Accurately measure the water loss over a 24 hour period with the circulation system running, and then repeat with the circulation switched off. If the leak slows down or stops when the circulation is off, it would appear that the leak is on the pressure side of the circulation system. If the leak gets worse when the circulation system is off, it is possible that the leak is somewhere on the suction side of the system. If there is no change in the leak, whether the system is running or not, then it's likely that the leak is somewhere in the pool shell.

If you think you have a leak on the pressure side of the circulation system, and you have a vinyl liner, check that water is not getting behind the liner at the return-inlet fittings. If the gasket is damaged, water can sometimes get past and behind the liner.

If the tests indicate that there may be a leak on the pipework, now is the time to get your local pool dealer in to pressure test the system.

If you think that the leak is somewhere on the shell, whether it is a vinyl liner or a concrete pool, it is often best to simply turn off the circulation system, and let the water level keep falling until it stops. When the water stops falling, - the leak must be level with the water line. If the water level cuts across a skin fitting or an underwater light unit, - that fitting is imediately suspect. If the pool has a vinyl liner, then you will need to carefully check the liner all along the final water line to check for tiny holes in the liner.

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END OF RESOURCES PAGE 6