3.2 In Pool Equipment

• 3.2.1 Skimmer Boxes (Photo)
  - Every pool needs a method by which the water leaves to be sent to the pump & filter. In most cases this is done through a Skimmer Box which is mounted in the side of the pool with its mouth centered on water level. (usually 100-150mm (4-6") below the top of the pool).
  
  • The skimmer usually has a 50mm (2") connection to go to the Pump & and another 40mm (1.5") connection to go to the drain in the deepest point of the pool.
    
  • The skimmer should be located such that normal pravailing winds blow debri on the water's surface into the skimmer.
  • "It can be at either the deep or shallow end of the pool it does not have to be at the deep end."
    
  • Normally one skimmer box will handle up to 60SqM (616 SqFt) of pool surface area. (after that use two skimmers) or 250 litres/minute (62.5 USG/Min)of pool water.

• 3.2.2 Main Drains(Photo)
  The main drain is located at the deepest point of the pool & incorporates:
  
  • 1. Connection to the skimmer box for drawing water from the base of the pool
    
  • 2. A Hydrostatic Valve in its base which is connected to an open tube below the pool floor. This allows any excess water pressure out side the pool to be released if the pool is emptied at any time.
  • The valve is one way & wont let water leak from the pool. (unless it is fitted incorrectly or has rubbish in it or is deterioated.

• 3.2.3 Return Eyeballs - The eyeballs are fittings which help control the direction of the water returning to the pool.
  
  • There should always be at least two eyeballs & some times more.
    
  • Work on the equation "one eyeball for each 75 litre/minute (18.75 USG/Min) the pump puts out."
    
  • Set the eyeballs to work in a circulating pattern to drive the debri to the skimmer box.
    
  • Set the Eyeballs at least 300mm (1.0') below the surface of the water & point then down towards the floor, not up to the surface
  .

  3.3 Pump Selection(Photo)

  
  
  • - Remember "All pool pumps are NOT created equal". But exactely which one you should use is also not an easy answer to give because all manufacturers are trying to beat each other on price so they all reduce costs & components to a minimum. Check the following:
    
    
    • To work out the size of pool pump you require divide your pool volume in litres by 4 or (gallons by 4)(the number of hours to pump all the water in your pool) & then divide by 60 (the number of minutes in the hour) EG if the volume is 60 Cubic Metres or 60000 litres 60000/4 = 15000/60 = 250 this is the minimum number of litres a minute (15000 US Gallons 15000/4 = 3750/60 = 62.6) gallons /minute that your pump will be required to pump.

    • Compare flow rates for pumps against a set pressure(HEAD) say 12 Metres or 120 kPa or 16 PSI, ask the sales person for the figures for each pump at that head, are you still getting the 250 l/min. or 62.6 g/m.
      If not then you need to go up one size in pump or look at a different pump.
      
    • Pumps come in different sizes, the 250 l/m (62.6gpm) will need about a 750-1000 Watt or 1.0-1.25 HP Pump, whereas 350 l/m or 87.5 gpm would need a 1200-1500 Watt or 1.5-2.0HP pump.

    • The cheaper pumps usually pump as much as the more expensive but can me much noiser in their operation so be careful with the cheapest in a given size.

    • Remember that pool pumps are surposedly made to go outside but you will find many have conditions in the warrantees which require "adiquate protection". It is a good idea to put the pump & filter & other equipment in a nice garden shed or garage or basement, the equipment will last years longer for the cost of a few metres of pipe & a few fittings.

  3.4 Filter Selection

  - Now that you know the flow rate of your pump, you can begin to select a filter for your pool. There are basically Three choises.
  
  

  • 3.4.1 SAND:(Photo)
    Sand filters are predominant, not necessarily because they are the best but because they are the easiest to look after. They consist of a tank with a specially screened sand inside & a multi port valve which allows you to control the water flow through the tank.
  • The valve has a FILTER cycle which allows the dirty pool water to enter the top of the tank & pass through the sand, leaving behind the dirt & then the water passes back through the valve & back to the eyeballs in the pool.
  • The good thing about the sand filters is that they are easy to operate, they have a midlevel capital cost & a relitavely low operating cost.
  • Select a sand filter by picking one that has a maximum flow rate at least 25% above the pump flow rate. EG if pump flow rate is 250 l/min 62.6 gpm then pick a filter with 320 l/min 80 gpm Max
  • If you are operating at above 300 l/min then buy a filter with a 50mm valve assembly, not a 40mm assembly & plumb the filter in 50mm pipe.

  • Always observe backwash line sizing recommendations.

• 3.4.2 DIATOMACEOUS EARTH:(Photo)
  These filters are not as popular as they used to be & are some times refered to as dinasor filters, as being old fasion & using decomposed fossils as the filter medium, but they are the finest pool filter units available.
  • The DE filter consists of a tank with cloth pads inside & a multiport valve which allows you to control the flow of water through the filter tank & pads.

  • The DE powder is added to the skimmer box & flows through to coat the cloth pads in the tank. (THE PADS ARE NOT THE FILTER, THE POWDER IS).

  • The DE collects the dirt from the water & when it has collected all it can hold, the earth & dirt combined are backwashed to waste, after which new DE powder is added.

  • Although DE filters are a little more work when cleaning is required, if sized correctly & operated correctly they will run a lot longer between cleans than a sand filter

  • Always pick a DE filter that will operate at at least 25% higher flow rate than that calculated for your pool.

  • Always observe backwash line sizing recommendations.

• 3.4.3 CARTRIDGE : - Cartridge filters can be very good if you use enough area, other wise you will spend a lot of time cleaning them, they are initially cheaper than the other options but a little more work & have a higher operating cost than sand filters.
  • Select your cartridge filter by selecting one or more equal to 30% of the surface area of you pool. Eg if you have 50SqM (550 SqFt)surface area then get a 15 Sqm or (155 SqFt)of cartridge filter.

  • You can size the filters up to 50% above the flow rate of your pump as the Cartridge filters are not dependent upon the pump volume for cleaning as the other filters are. EG a 15SqM or (155 SqFT) filter can operate happily at 350 l/min or (87.5 gpm).

  • The only down side with a cartridge filter is that you have to physically take it out & wash it by hand using a high pressure hose & at regular intivals you will need to soak it in a cartridge cleaner solution to remove body fats & chemical build ups.

3.5 Pipework Selection