Water is pumped from the pool through a filter and back to the pool again. The pool skimmer box or boxes is where the pump sucks the water from the pool. The filtered water is then returned to the pool through jets or outlets in the walls or floor.
How long you need to run the pump and filter for depends on the size of your swimming pool and the size of your pump and filter. As a general rule of thumb most systems run for 8 hours per day during summer and 3-4 hours per day in winter. Even when running correctly approximately 35% of your pool water still won’t get filtered due to design and economics of pool construction (according to a Victorian Government Fact Sheet). Although your pump and filtration system may filter the entire volume of your pool several times over during the daily running time, there will be dead spots in the pool where the water does not move or circulate well. For this reason all pools can benefit from the use of a clarifier or enviro pool stick. The enviro pool stick in particular can then oxidize and remove bacteria and organic particles from these dead spots and gets constantly moved around the pool by pool cleaners and pool use.
There are two main types of pool filters: Sand and Cartridge.
Sand filters generally filter down to 20-30 microns while cartridge filters filter a bit smaller down to 15-20 microns (1 micron = 1 millionth of a metre).
Sand filters are the most common type used on pools. With these filters; dirty water is pumped into the top of the filter where it flows down through the sand trapping dirt particles as it goes. Clean water then flows out the bottom back to the pool.
To clean sand filters, the water flow is reversed so it flows from the bottom of the filter to the top taking all the trapped dirt particles out the backwash drain. As the water flows up through the sand it agitates and loosens the dirt particles cleaning the filter.
This process is activated by the BACKWASH VALVE. This valve is located on top of the filter or on pipework attached to the filter. The valve has a number of settings on it including: Filter, Backwash, Rinse, Closed, Recirculate and Waste.
Filter position: is the normal operating position allowing the water to pass through the filter, cleaning it as it goes and returning it to the pool.
Backwash position: reverses the water flow through the filter to dislodge and remove dirt particles trapped during filtration. Most sand filters have a sight glass or clear section of pipe so you can see how dirty or clean the water is. When the water becomes clean backwash can be stopped. The valve can then be moved to the rinse position.
Rinse position: allows the water to flow through the filter in the normal direction but instead of returning to the pool it flows down the drain to clean out any dirt particles left after backwash.
Closed position: stops water from going anywhere. The pool pump should not be operated while the valve is closed as this could result in damage to the pump and associated equipment. Never leave the valve in this position.
Recirculate position: allows the pool water to flow through the valve and back to the pool without going through the filter. This position is mainly used to mix chemicals at a quicker rate.
Waste position: allows the water from the pool to go straight down the drain. This is used during cleaning if the pool floor is exceptionally dirty or the pool has been flocked protecting the filter from excessive loading. It can also be used to drain some water from the pool and lower the water level.
Always shut off the pump when changing the backwash valve position to avoid damaging the pump, valve and pipework.
Cartridge Filters – are a very simple filtration system. They consist of a thin woven material in the shape of a cylinder; this is called the cartridge. The cartridge fits inside a tube or housing with a lid for service and cleaning. The pool water passes through the thin woven material trapping the dirt particles on the outside. Clean water then flows from the centre of the cartridge back to the pool.
To clean cartridge filters, the lid needs to be removed from the housing, the cartridge taken out and hosed down to wash off the dirt. If it cannot be cleaned the cartridge can be soaked in cleaning solution or replaced with a new one.
Cartridge filters can filter as fine or finer than sand filters, they also use less water to clean the filter and take up less space making them just as popular as sand.
When to clean your Filter
Most filters have a pressure gauge on them. As they become blocked, the pump has to work harder to push the water through therefore the pump pressure increases and the pressure gauge reads higher. Once the pressure gets to a certain point the filter needs to be cleaned. If the filter does not have a pressure gauge you will have to keep checking the flow rate or amount of water returning to the pool; as the filter becomes blocked less and less water will be pumped back to the pool.
As a general guide the filter should be cleaned when the pressure gauge reads 30-40 kpa more than when the filter is new and clean i.e. if the pressure gauge reads 30 kpa when the filter cartridge is new, then it should be cleaned when it reads between 60-70 kpa.
What Makes the Pool Dirty and blocks the filters
Baby oils, suntan oils, body fats, hair oils, perspiration and other similar organic particles. These oils bind together with other particles creating a film over the filter surface and making it very difficult to clean the filter. An Enviro Pool Stick will oxidize these oils and any other organics in the water before they get to the filter reducing the maintenance, costs of running the pump and filtration and reduce the need to chemically clean the filter.
The pool stick will also in most cases considerably reduce the chlorine usage and level in the pool.
Most pools have a skimmer box which also serves as an intake for the pump and filter system. The skimmer box is designed to collect or skim any rubbish and other floating debris from the pool surface. It is best to skim any debris off before it sinks to the floor and has to be vacuumed.
Skimmer boxes usually contain a “basket” or strainer to collect larger items such as leaves. This basket needs to be removed and cleaned regularly to avoid damage to the pump from a blocked suction line. The pool water level should always be high enough to freely flow into the skimmer box.
Pool cleaners and vacuum devices are also usually connected through the skimmer box.