Pool Types

There are two types of pool, domestic and commercial, where domestic pools are constructed for individual usage and the commercial ones being pools installed for public use like the case of schools, hotels or even municipal installations. These can further be classified as “free board”, “deck level” or “horizon” based on the circulation system.

“Freeboard” is the standard pool type with the water level 50 mm to 100 mm below the top of the wall tiles and a surface skimmer to remove leaves and other floating debris.

“Deck level” level pools have a peripheral overflow channel and a balance tank. When the pump I running, water is taken from the balance tank and pumped into the pool until it overflows into the channel and then back to the balance tank.

  “Horizon” pools are a variation on the deck level concept but without the peripheral channel The top of the pool wall where the water will overflow is built 50 mm lower than the rest to create the “horizon” effect.

Filters

The filter is designed to remove suspended solids from the pool water. For domestic pools where bathing loads are light, the pump will circulate the pool water through the filter every eight hours. For pools with higher bathing loads the circulation rate is higher, typically four to six hours.

Pressure Sand Filters

These are the most commonly used filters in Kenya. Dirt and other deleterious materials are removed from the water by forcing it through the filter media, which consists of layers of carefully graded river sand. Pressure sand filters are rated according to the volume of water passing through every hour divided by the effectiveness of the filter media. Modern fiberglass filters are effective with a flow velocity of up to 50 m/hr.

Maintenance of Filters

Dirt removed by the filter will accumulate in the filter media and this eventually leads to clogging. The larger size filters have a pressure gauge on the inlet, which can be used to access whether the filter media needs cleaning. When the filter is operating effectively the operating pressure will typically be between 0.6 and 1.0 bar (10 to 15 psi). As the filter becomes blocked the pressure will rise and an increase of 0.3 bar (5 psi) indicates that it should be cleaned. This will involve backwashing and rinsing (for pressure sand and DE filters) or hosing down of elements (for cartridge filters). If no pressure gauge is supplied then the filter should be backwashed on a regular basis, normally once a week being sufficient.

Use of Multi-Port Valve (MPV)

Most modern filters are fitted with a multi-port valve (MPV) to simplify filter operation. There are six positions on the MPV and the various operations possible with the different settings are described below.

MPV Operation

Filter

This is the normal operating position. Water from the pump is fed into the top of the filter and after filtering through the media is collected at the bottom.  It is then returned to the pool through the inlet pipes.

Backwash

When the filter becomes clogged, the MPV should be turned to BACKWASH. Water will now be pumped from the pool into the bottom of the filter and out of the top.  It is then discharged to waste.  This operation normally takes two to three minutes and should be continued until the water in the sight glass on the side of the MPV is clear.

Rinse

After backwashing the filter media needs to be rinsed.  Water is pumped into the top and out of the bottom of the filter as for normal filtering but the water is then discharged to waste.  This removes any residual dirt in the media instead of pumping it back into the pool.  Rinsing should not take more than one minute and again the sight glass on the side of the valve can be used to see when the water is clear.

Recirculate

In this position the filter is by-passed completely and the water is pumped straight back into the pool.  It will normally only be necessary to use this option if there is a problem with the filter itself (e.g. a leak or a major blockage).  It can also be used if the filter is on a spa bath to increase the pressure at the hydro-jet inlets.

Waste

The waste port is used for emptying the pool.  The filter is by-passed and water is taken straight from the pool to waste.  If it becomes necessary to empty the pool make sure that the pump is not switched off once the operation has began as there may be problems with priming the pump when the water level is low.  This position can also be used for vacuuming to waste.  This may be necessary if there is a large amount of sediment on the floor of the pool, which would rapidly clog the filter in normal operation.

Closed

This shuts off all flow to the filter and the pool.  It is usually used in conjunction with the valves on the suction side of the pump to prevent water loss when it becomes necessary to remove the lid of the line strainer to clean the basket.

WARNING: WHENEVER THE POSITION OF THE MPV IS CHANGED THE PUMP MUST BE SWITCHED OFF OR THE MPV MAY BE DAMAGED.

Chemicals

It is important that you understand the role of the various chemicals used to keep pools clean. Basically, if the water in the pool is clear and blue, the following three conditions should be satisfied:

1. The acidity-alkalinity balance is correct,
2. All algae and bacteria have been eliminated, and
3. All suspended solids have been removed.

The object of treating the pool water is to maintain these balances. If any of them is allowed to get out of control then the water in the pool will not be sparkling blue.

Acidity-Alkalinity (pH)

The balance between the acid and the alkalines in a pool is measured on the pH scale, which can vary between 1 and 14. Distilled water has a pH of 7.0 (neutral) and the ideal pH for pool water is between 7.2 and 7.6. If it is allowed to go higher than this (too alkaline) the water may become cloudy and the effectiveness of chlorine to kill bacteria and algae will be reduced. If the pH drops below 7.0 (too acid) then steel fittings will start to corrode and the water will irritate swimmers' eyes. The effectiveness of chlorine will also be diminished. pH can be easily measured using a test kit, which has a colour-coded comparator for easy reading. When a pool is first filled the pH should be tested daily until a consistent reading is obtained. There after testing need only be done once a week or even less frequently if the water remains clear and blue.

pH too high (above 7.6)

If the pH is too high it must be lowered by the addition of acid. The acid can either be in granular or liquid orm and is marketed as “HIGH PH” or “pH MINUS". The dosage rates to reduce the pH will be indicated on the package.

For liquid acid approximately 60 cc (gms) of acid will be required for each 0.1 reduction in pH for each 10,000 litres (10m3) of water. 

After adding acid the water should be allowed to circulate for four hours before testing again. If the pH is still too high then the procedure outlined above should be repeated.

pH too low (below 7.2)

If the pH is too low it must be raised by the addition of soda ash (sodium carbonate) which is marketed as “LOW PH” or “PH PLUS”. The procedure is the same as outlined above for reducing the pH but the dosage rate is 50 gms per 0.1 increase in pH per 10,000 litres. 

As soda ash is a powder it is best to pre-mix it with water before pouring the concentrated solution into the pool.

The checking and re-application procedure is as for high pH.

Sanitation and Removal of Algae and Bacteria

Sanitation and Removal of Algae and Bacteria

This section deals with disinfecting the pool water to keep it free from harmful bacteria and algae. If algae are present in large enough quantities the pool water will turn green and one of the methods outlined below can be used to make sure that this does not happen. Algae can also manifest itself as a black growth between the tiles or in crevices in the pool wall or floor.

Chlorination

By far the most common treatment to kill algae and bacteria is to add chlorine, which is a powerful oxidizing agent. It can be obtained in many forms including gas, liquid, powder, granules and tablet. For safe and effective disinfection regular dosing is necessary so that there is a residual chlorine level of 1.0 part per million (ppm). This is normally achieved by adding 1.5 to 3.0 ppm of available chlorine, the most effective time for treatment being in the evening as chlorine is oxidized by sunlight. The weight of chlorine to add will depend on the quantity of free chlorine in the various products available.

CHLORINE "65": Also known as Calcium Hypochlorite, chlorine "65" is a granular form of chlorine and as the amount of available chlorine is 65%, the daily dosage rate is 25 gm for every 10,000 litres if the water is clear rising to between 75 and 150 gm for 'shock' treatment.

CHLORINE "90": This is a powder form of chlorine with 90% available chlorine. The base is trichloro-isocyanuric acid and its use has the added benefit of reducing the chlorine loss from sunlight. The daily dosage rate can thus be reduced to 15 gms for every 10,000 litres when the water is clear and blue or 50 gms for CHLORINE "65" and CHLORINE "90" is often recommended as it helps to stabilize the water.

Salt Water Chlorinators

A method of chlorination rapidly gaining in popularity is the saltwater chlorinator. This works by generating chlorine from salt dissolved in the water. For the unit to operate, refined salt must be added to the water to raise the salinity to 4000 ppm; for a pool with a volume of 80m3 this means adding 320 kg of salt. The water will therefore taste very slightly salty (similar to the well water at the coast) but will not be sufficiently saline so as to cause red eyes (for comparison, sea water typically has a salinity of 40,000 ppm). The salt concentration should not be allowed to fall below 3000 ppm. Salt-water chlorinators have the advantage of producing chlorine on a continuous basis rather than the batch dosing needed for powder or granular chlorine.

Algaecide

Under normal operating conditions chlorine dosing will be sufficient to kill any algae in the pool water but if certain types of algae do become established, an algaecide must be used. This is marketed as "MAGIC TOUCH" or "ALGAECURE".

"MAGIC TOUCH" is an organic algaecide, which can also be used to improve the clarity of the water. The dosage rate is 200ccs (gms) per 10m3 (10,000 litres) and a single dose is normally sufficient to kill all the algae in the pool. However, if growth is still apparent after three days, the dosage should be repeated.

"ALGAECURE" is a copper-based algaecide. After dosing with 400 cc (gms) per 10m3 (10,000 litres), the pool water should be circulated for 24 hours. The algae can then be removed by using a stiff brush. If necessary the treatment can be repeated to remove particularly stubborn algae.

Removal of Dirt

Occasionally it may be necessary to remove solids suspended in the water (rather than dissolved in it). This normally occurs when the pool is first filled-especially if borehole water is used. As larger size dirt particles quickly settle to the bottom of the pool where they can be removed by vacuuming or brushing, they do not present a problem. But as the particle size decreases the settlement time gradually increases and the smallest size particles remain permanently in suspension. In order to remove these particles, the water must be dosed with flocculant which sticks to the soil particles thus effectively increasing their size and weight. They then settle to the bottom of the pool (a process called flocculation) where they can be removed by normal filtration or vacuuming. The quantity of floculant to be added will depend on the amount of dirt in the pool but initial dose of 50 ppm is normally recommended. This works out at 500 for every 10 m3 (10,000 litres) of water.

Flocculant is supplied in granular form so it must first be premixed to form a concentrated solution before it is added to the pool. The concentrated solution should be poured around the edge of the pool and the pump should be kept running for three to four hours to make sure that it is mixed effectively. Alternatively, the flocculant can be placed in the line strainer on the pump where it will gradually dissolve while the pump is working. The pump should then be switched off and the particles allowed to settle preferably overnight. Any sediment dirt can be removed by filtration. This can sometimes take two to three days if the water is particularly dirty or if there is a large proportion of clay sized particles.

hth “Sparkle It”

“Sparkle It” is a recently introduced water clarifier which clears cloudy water and aids filtration. It contains liquid flocculators and should be used when the pool water is cloudy or lacks sparkle. Add up to 1 litre of sparkle It to the skimmer basket or to the line strainer and the n allow the water to circulate for 12 hours before switching the pump off and leaving – preferable overnight. The dirt deposited can then be vacuumed off the pool floor. The filter should then be backwashed.

Anti-Stain

Anti-stains are detergents specially formulated for use in swimming pools. They are effective in the removal of scum from the top tile layer as well as for cleaning handrails and other exposed pool accessories. It is normally applied by cloth but where the staining is excessive a scouring pad can be used.

Pool Water Level

Maintenance of the correct pool level is most important to ensure proper operation of the skimmers in a freeboard pool or the peripheral drains in a deck level pool.

Freeboard Pools

The correct level for freeboard pool is approximately half way up the skimmer mouth or about 100 mm (4ins) below surround level. The level can be raised to improve the aesthetics of the pool. The level of the pool will drop when the filter is backwashed or rinsed and as a result of evaporation. Periodic refilling will therefore be necessary and this is normally done with a hosepipe connected to a stamp pipe.

Deck level and Horizon Pools

The correct level for deck level and horizon pools is the top of the wall but for these pools it is the amount of water in the balance tank that is critical for correct operation. The pool is considered to be full when, with the circulation pump off, the water in the pool is at the top of the pool walls and the level of the water in the balance tank is 600 mm (2ft) below the top of the balance tank. The water level in the balance tank should be checked periodically and replenished as necessary. It is important to note that over-filling the balance tank can result in water overflowing from the tank and under-filling will affect the efficiency of the peripheral drainage system. However, if there is a shortage of water and the level in the balance tank is too low for the overflow to operate, the valve from the balance tank should be closed and the pool operated as a freeboard pool using the main drain only.

Heating

The principal cause of heat loss in swimming pools is through evaporation and if the temperature of the pool is to be maximized by installing a heater then steps must also be taken to reduce heat loss. This can be achieved by fitting an impermeable floating cover and owners who want to heat their pools are strongly recommended to fit one. There are various types of heater available details of which are given below:

Solar Panels

There are various types of solar heating designs, though all use the principle of pumping water through a collector, which absorbs heat from the sun. Some designs are enclosed in panels and there are exposed pipes connected to the manifold. Modern panels are made from flexible PVC and typically measure 3.0 m x 1.2 m. For effective heating the panel area required is between 60% and 70% of the surface area of the pool. The solar panels must be positioned so that they receive the maximum amount of heating during the hottest hours of the day. Careful consideration must also be given to the aesthetics of the installation. The system works on a by-pass system with three valves.

Electric Heaters

Electric heaters are designed to combine simple operation with high thermal efficiency. The heater consists of a series of immersion heaters arranged in banks of 9 kW, each bank being controlled so that heat output can be adjusted according to the requirement. The heater is installed after the filter and all the water returning to the pool is pumped through the heater. This in-line arrangement ensures that heat loss is minimized and all the heat energy is transferred to the water. The heater is installed complete with a control panel, which incorporates an electrical interlock so that the heater will not work unless the pump is switched on. The panel also has switches to isolate the mains power, a timer switch for automatic operation and switches for the individual banks of heater elements. Note that MCB protection is provided inside the panel on all circuits. If for any reason the pump or heater will not work, check that all the MCBs are "ON". If they are "ON" and the equipment will not work or if after resetting they immediately re-trip, a qualified electrician should be called to check the installation. As a result of their high power ratings, most electric pool heaters operate on three-phase power.

Heat Pumps

Heat pumps work by moving heat from one place to another; in this case from the air to the pool water. Imagine a refrigerator in reverse. Whereas a fridge expels air from an enclosed space to the surrounding atmosphere, a heat pump sucks heat from the ambient air and transfers it to the pool water. In general, a heat pump will transfer 5 or 6 units of heat for every unit of unit of energy consumed. Although the initial cost is more than other heating methods, the running costs are considerably lower solar panels excepted).

To heat the pool, the heat pump may initially have to left on for 24 – 48 hours but thereafter (as long as the pool is covered at night) it will keep the pool at the desired temperature operating for 2 – 3 hours daily.

Heat pumps are installed on a by-pass arrangement on the delivery line to the pool and so can be fitted retroactively.

Under Surround Heating

Under-surround heating works by diverting the water being returned from the filter through a series of pipes built into the pool surround. On a hot day the pool surround is warmer than the water in the pool and as the water flows through the pipes it absorbs heat. The warmer water is then returned to the pool via the inlets. The system is also operated on a by-pass system. For optimal heating effect, the under surround system should be operated during the hottest hour of the day (10.00 am to 4.00 pm). Effective heating will only be obtained when there is direct sunlight on the surround and the system will be ineffective when shaded either by cloud or trees. As this system only works when the surround is hotter than the pool water it will cool the pool if left on overnight.

Cleaning Equipment

Not all the dirt or leaves that fall into a pool will be removed by the filter system and a variety of brushes and cleaners are available to help with maintenance.

All our new pools are provided with:

• A pool broom for brushing the floor of the pool. This can be used to move any dirt on the floor towards the sump so that it is then removed from the water by the filter.
• A scrubbing brush for helping to dislodge any algae that may have become attached to the walls or floor.
• A leaf skimmer or leaf rake for removing any leaves that are floating on the surface of the water or which have sunk to the floor of the pool.
• A vacuum cleaner to keep the pool floor clean. The vacuum head is connected by a flexible floating hose either to the skimmer or to a special vacuum point in the pool wall.

Automatic cleaners are also now available. These do essentially the same job as a vacuum cleaner but without the manual input! The most popular model on sale is the "Baracuda". It operates in a similar manner to a vacuum cleaner, the only difference being that the "Baracuda" moves around the pool in a random pattern.

Trouble Shooting

Well cared for pool water will last indefinitely. Water lost through evaporation can be replenished from the mains or when it rains with very little effect on the overall chemical balance. However heavy rain can add substantial amounts of water in the pool and this can lead to a rapid growth of algae. It is therefore essential that the chlorine level and pH be tested after heavy rain and the water treated accordingly.

Pool Water is Green

Green pool water is caused by a build up of algae. This condition can be cured by, first checking the pH, adjusting if necessary and then shock treating with chlorine. The pump and filter should then be left on for at least twenty-four hours to disperse the chlorine uniformly throughout the pool. If the water is still green at the end of this period, check the residual chlorine level using the colour coded comparator in the standard test kit and if necessary repeat the dosage.

Pool Water Cloudiness

Pool water cloudiness is more often than not caused by high (and sometimes low) pH. Adjusting the pH to between 7.2 and 7.6 will usually cure this problem though it may be necessary to run the filtration system for 24 hours to get clear water again. It should be noted that if the pH is either too high or too low then the effectiveness of the chlorine will be reduced and if the water is also green then shock treatment with chlorine will be necessary once the pH is within the correct range.

Coloured Water

Coloured water (reddish brown or brownish black) usually indicated the presence of iron or manganese. This can occur if steel circulation pipes start rusting and also if certain types of borehole water are used to top up the pool. In either case the solution is to flocculate, shock treat the water with chlorine and then to either remove sediment with a vacuum or by letting the filtration system operate continuously for 24 hours. It should be noted that if there is a significant amount of sediment to be removed then the filter will have to be back washed more frequently than normal to avoid clogging.

Pump Failure

There will be times when the pool pump will break down and in these circumstances it will not be possible to circulate or filter the pool water for some days. In this situation continue to treat the pool water with double the normal daily chlorine dosage whilst monitoring and adjusting the pH as necessary. This will ensure that the water remains sanitized and although there may be an accumulation of dirt the water will remain in an acceptable condition for short periods. It should be noted that, even if the water gets very dirty, once the pump is operating again, the filter system will be able to clean it and it is unusual to have to empty and refill the pool with fresh water.

Faulty Filter

If the filter becomes defective it can be by-passed by turning the MPV to "RE-CIRCULATE". Chemical dosage should be doubled and the pH should be monitored as normal. When the pump is operating the chemicals will be dispersed uniformly but there will of course be a build up of dirt over time. This can be easily removed once the filter has been repaired.