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A swiming pool is made up of water and a number of complex chemicals that need to be kept in perfect balance with each other, in order for the pool to maintain its appeal and safety for swimmers. Bathers complaining of sore eyes and dry skin can often be a sign of water that is unbalanced. Keeping a clean pool is just a case of good housekeeping and understanding of the chemicals needed.

This is not an exhaustive manual, but it covers the basics that any domestic pool owner will come across.

Swimming Pool Chemicals are dangerous. They are corrosives that will cause severe burns. Always wear gloves and goggles when handling them. The door to the pump house should be kept shut to keep animals and children away from the electrics and chemicals.

The pump removes the dirty water from the pool by sucking surface water through the skimmer(s) and through the drain in the bottom of the pool. This water is forced through the filter under pressure and is then returned to the pool through the jets at the opposite end of the pool. The skimmer removes surface debris by drawing surface water into the skimmer basket. The main body of water is filtered by drawing it through the drain in the bottom. Both of these are necessary because if only the skimmer was working, the dirt in the water would sink to the bottom of the pool. If only the drain was working, then any insects or leaves landing on the surface would not be removed.

The skimmer will not work if it is entirely submerged, the water level must be a couple of inches below the top, otherwise it will not suck off the surface of the water.


To help the filter and the chemicals do their job, the following needs to be done daily.

Empty the skimmer basket.
Scoop out any large debris.
Run pump on filter.

Other jobs listed in this manual can be done on a weekly basis, but an eye should be kept on the condition of the water. You can often tell if there is something wrong because the water loses its sparkle.


The electric pump which circulates the water must be run for at least 2 hours every day to keep the pool clean and prevent it from seizing.
Water is filtered, under pressure through a tank filled with sand. The sand in the filter traps particles of dirt carried in the water. The filter also catches bacteria and algae. On the top of the filter is a pressure indicater, if this strays into the yellow or red, IMMEDIATLY SHUT OFF THE POWER and check the trap and filter.
Once a year the top will have to be taken off the filter and the sand level topped up. Each time that the pool is backwashed, some of the filter medium is lost. Filter sand is on sale with the chemicals. It is a special sand that has been washed and graded- too small it would escape into the pool water and too large it would not trap particles.


In a typical domestic swimming pool pump house there will be four valves (taps) that control the flow of water around the pool. These should be set as follows for normal running-
(open position the valve runs parallel to the pipe- closed it is at a right angle to the pipe)
the OUTLET valve should be in the OPEN position
the DRAIN valve should be in the OPEN position
the SKIMMER valve should be in the OPEN position
the VACUUM/ HOOVER valve should be in the CLOSED position

there is also the FILTER valve which can be set to various different positions, depending which direction the water is to run through the filter. Do not turn this valve whilst the pump is running.
The FILTER valve should be set to FILTER.

3.2 TRAP (in pump house)

Before water reaches the filter there is a trap for large particals, such as leaves, stones or twigs which would damage the pump. This trap has a clear plastic lid, beneath which is a basket. To empty this basket, turn off the pump (and timer), turn off all the valves that lead to and from the swimming pool (there is usually 3 in and 1 out). This will stop excessive amounts of water flooding into the pump house when the lid is removed. The lid unscrews and once it has been removed the basket can be lifted out (this may need to be twisted). Once the basket is removed, knock out any debris, rinse the basket and replace.
Screw the lid back on and turn the valves back to the original positions.
If the timer was turned off, turn it back on and turn the pump back on.


If the pressure is reading high, even after emptying the trap, the filter may be clogged. The filter is cleaned by reversing the flow of water through it. The water that comes out is pumped to a drain and does not go back into the pool. You may also notice that whilst hoovering the return flow to the pool slows down.
Turn off the pump.
Turn the lever on the filter control valve to the backwash position.
Turn on the pump.
On the side of the filter valve there is a small glass bubble. The backwash water flows through this and the water in the bubble will turn clear once the filter is clean.
This normally takes 2- 3 minutes.Turn off the pump.
Turn the valve to the position that says rinse and run the pump again for 30 seconds.
Turn off the pump.
Turn the valve back to the filter position and turn the pump back on.
Check the pressure.


To operate the hoover, attach the pipe to the hoover brush and then feed the pipe under water to remove the trapped air and then connect to the socket.

In the pump house turn off the inlet valve from the skimmer and turn off the inlet valve from the drain at the bottom of the pool. Turn the hoover valve on.
(The filter valve should be in the filter position, however if the pool is particularly dirty, set the valve to waste. You must keep an eye on the water level. If in doubt, leave the valve in the filter position).
Turn the pump on. Gently hoover the debris off the bottom of the pool.
The hoover only works properly when it is pushed away from you.

Once the hoovering is finished, turn off the pump and set the valves back to the correct positions and remove the vacuum pipe. Turn the pump back on and check the filter pressure. If the pressure is high, check trap and back wash if necessary.
If you had the valve set to waste, check the water level and top up if necessary.

A device such as a Kreepy Krawly or similar can be fitted to a pool. This device automatically hoovers the base and sides of the pool whilst the pump is running. (check compatibility with your pool before fitting). These are only designed to suplement normal hoovering.


The purpose of the chemicals is to balance the water so that bacteria and algae can't grow in it, but at the same time keep it safe for people to swim in without injury.
Chemicals all do different jobs, but they need to have certain conditions in order to do their jobs properly.

The most important factor is maintaining the correct acidity level, the other chemicals will not work properly otherwise.

A basic water test looks at the amount of chlorine and acid present in the pool water. For domestic swimming pools this test is adequate as there is not enough load on the water to drastically alter free chlorine levels or effect dissolved solids levels or total alkalinity levels.

If the water in your area is hard (does your kettle fur up?) then the water has to be treated  with acid in a different way than if it was soft.

Remove the lids from the tester and rinse it in the pool. Empty it out and then turn it upside down. Lower it into the water to elbow depth then allow it to fill up. Samples must be taken from below the surface to provide an accurate reading, as sunlight breaks down chlorine molecules.
Empty out water from the phial until it is at the 10ml level. Add the phenol red (5 drops) and the OTO (5 drops). Replace the lids and shake well. Compare the colours with the colours on the scale. The correct levels are

            CHLORINE 1 - 1.5ppm
pH 7.2 - 7.8 (permissible but in hard water areas should be 7.2)

For hard water areas, the acidity needs to be kept as near to 7.2 as possible. Keeping the water as near to being acidic will help to reduce lime scale build up.

The pH level has to be kept between 7.2 and 7.8 otherwise the chlorine would not work.
To reduce the pH level, you will need to add products labled pH MINUS or PLUS ACID.
These products should not be added straight into the pool water. They must be dissolved in a bucket of water and added to the deep end of the pool. The reason that they must first be dissolved is the fact that they are very dangerous and can cause severe burns. If the granules are added to the water it would create a spot of concentrated acid.
They must be added to the deep end because this allows the acid to be diluted as quickly as possible. Always wear gloves and goggles when handling chemicals.

If the pH needs to be raised follow the above method but using products labled pH PLUS or MINUS ACID.

To add the GRANULATED chlorine scatter it across the surface of the water, but ensuring that you are not down wind. You should wear goggles and gloves.
If using chlorine tablets, they are normally put into the skimmer baskets, which helps the chlorine to dissolve at a steady rate. There can be problems with the equipment later on as the chlorine is very corrosive and will make the plastics brittle. The first signs of this will be the flaps falling off and the skimmer baskets breaking up.

4.1 How much to add ?

Roughly work out the size of the pool by pacing out the number of metres. Calculate the average depth. Multiply the three figures together to give a cubic metre measure. The specific chemicals used will have different dosing levels according to their individual make up, but dosing levels are always calculated on cubic metres. However the easiest is thing is to add a little and then test again later. You will soon learn how much you need to add. If you test on a weekly basis the aim is to have residual chlorine in water 7 days after the chemicals were added. If there is no reading when testing, then add more.
Adverse weather conditions or increased use of the pool will also mean that more chlorine needs to be added.


Floculants are a group of chemicals that when added to the water, bind small particals together so that they can be filtered out. They are normally added when the water is cloudy. Floculants usually come in a liquid form.
The correct way to use them is to take a bucket of water out of the pool and add floculant to this and then add to the shallow end.
For heavily clouded water run the filter for half an hour then turn off. The following day the particles will have settled to the bottom of the pool where they can be hoovered up. The filter will probably need back washing after this.
If the pool has just lost its sparkle, add a little floculant and leave filter running.
The dosage is dependant on the cubic metre size of the pool. Never add as much as the instructions say immediatly, as you will have residue on the bottom of the pool for weeks. You can always add more afterwards.


From time to time the sand in the filter will need to be topped up as a small part is lost each time the filter is back washed.
The sand is available from the same places as the chemicals. Fill the filter to about 6 inches from the top and replace the lid.
Backwash the filter and then rinse, before using the new sand for filtration.


In winter many people allow pools to go green or they drain them.
Draining pools is not good practice for a number of reasons. The walls of a swimming pool are designed to have pressure on them and are built as such. The water in the pool pushes against the sides outwards, if this pressure is taken away the sides of the pool can crack. Continually draining and filling a pool agravates this problem and can lead to costly problems. Grouts and tiles can start crumbling because they are simply not designed to be wet and dry (shrinking and expanding) Obviously if work needs to be done then draining it is unavoidable.
The second reason for not draining a pool is cost. A swimming pool takes a long time and a lot of money to fill (if on a meter, can be hundreds of euros). Water in a pool can normally be cleaned up in a short space of time.
If the pool is allowed to dry out, lime scale will be deposited. This will make the pool water lose its sparkle when refilled.
It is also important to note that you could be liable for injuries to a person that fell in an empty swimming pool as insurance policies say that a pool should be full.
In winter it is important to run the filter and scoop out leaves to keep the water clean. Chlorination can be reduced because there are no bathers or a lot of strong sunlight. As long as the water is kept free of debris it is an easy task to get it balanced for swimming in. If you have a cover it is recommended that this is fitted.

Allowing the pool to repeatedly go green will cause permanent staining.

Remember that if you have a heated pool, you will still have to add the same amount as you did during the summer months as the ambient temperature of the water encourages algae and bacteria to grow.