Circulation Systems

All modern pools come complete with a circulation system for keeping the pool water clean. The cycle is: pool -> pump -> filter -> pool.

As mentioned above, the most common piping layouts used to achieve this are the established "Freeboard" pool with the water level approximately 50 mm to 100 mm (2” to 4”) below the top of the pool wall and the “deck level” arrangement where the water flows over the wall into a peripheral channel at the same level as the pool surround.

The plumbing for the two systems is essentially the same with water being drawn from a main drain at the deepest part of the pool and from either a surface skimmer (for freeboard pools) or a balance tank (for deck level and horizon pools). A third suction point for a vacuum cleaner is also included on all our pools. There are thus three suction lines leading to the pump and can be controlled individually by an isolation valve.

Operating Procedure

Under normal conditions the valves from the skimmer (or balance tank if the pool is deck level of horizon) should be fully open, the main drain should be partially open and the vacuum line closed. This ensures that the water is drawn from the deepest part of the pool as well as from the surface thereby optimising circulation.

The pool circulation system should always be in operation when the pool is being used. When not in use it is normally sufficient to switch the pump on for four to six hours a day to keep the water clean. During the cold months when the pool is not in use for long periods, the operating time can be reduced. The exact pumping time is determined by the individual pool conditions.

ON DECKLEVEL AND HORIZON POOLS THE ISOLATING VALVE TO THE BALANCE TANK SHOULD BE CLOSED WHEN THE PUMP IS SWITCHED OFF.

Skimmers

Skimmers are installed on "Freeboard" pools to remove floating debris from the water surface. The effectiveness of the skimmer can be increased by slowly closing the isolating valve from the main drain while the skimmer valve is left open. The skimmer basket should be checked and cleaned every week as part of the routine maintenance of the pool. Always make sure that the floating weir (if fitted) is working properly as this has a direct effect on skimmer efficiency. If the water level in the pool is below the skimmer mouth then the skimmer valve should be closed completely to avoid the risk of the pump sucking air into the system.

Vacuum

Pool vacuum cleaners are very effective in removing dust and debris that can accumulate on the floor of the pool. The cleaner operates by sucking water through the vacuum head via a flexible floating hose to the vacuum line and thence to the pump and the filter. The floating hose should be filled with water and connected to the vacuum point in the pool wall. The vacuum valve in the plant room (which is normally closed) should then be opened and the sump and skimmer/balance tank  valves closed. The vacuum head should be moved slowly across the pool floor to avoid stirring up the dirt that has settled to the bottom of the pool. When vacuuming is complete make sure that the valves in the plant room are returned to the normal operating position.

NB: DO NOT USE THE VACUUM TO REMOVE LEAVES FROM THE BOTTOM OF THE POOL AS THEY MAY BLOCK THE VACUUM LINE. LEAVES SHOULD BE REMOVED WITH THE LEAF RAKE PROVIDED.

Pumps

A typical pump for a domestic pool consists of an electric motor turning an impeller inside the pump housing. A pre-filter or line strainer is usually incorporated into the pump body. This has a small plastic strainer for collecting leaves, lint, hair etc. and prevents such deleterious material from being sucked into the pump itself. The basket can be removed for periodic cleaning by undoing the clear plastic cover on the line strainer. To clean the line strainer proceed as follows:

1. Stop the pump and isolate the suction pipes by closing the main drain, skimmer (or balance tank) and vacuum valves.
2. Turn the MPV filter valve lever to "CLOSED"
3. Open the cover, lift out the basket, clean and replace it. Carefully check the seating for the lid when it is replaced, as it must be secured tightly to eliminate air leaks.

Pumps are rated according to the power (HP or KW) of their motors; the more powerful the motor the larger the volume of water pumped in a given time. Domestic pool pumps typically vary from 0.75 HP (0.55 KW) to 1.5 HP (1.1 KW). The pump motor has a thermostat built into the motor windings, which automatically protects it from overheating. The motor itself is a brush less design and as such it does not need routine maintenance. As for the filter, the size required for a particular pool will depend on the volume of the pool and the pump must be capable of cycling the water through the filter within the desired eight hour cycle time.

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.

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.