Replacing Sandfilter Media

- every 4 years or so it's time to replace the sand in the filter, and this is how you do it: -                                                                                  

  • Switch the pump to ‘Off’ and close all Valves
  • Remove the lid of the filter and, immediately underneath, you will seea plastic fitting that looks like a large-hole watering-can sprinkler rose
  • This is the ‘diffuser’ and must be removed from the filter by gently twisting and pulling, to allow access to the inside of the filter
  • Notes: -Some filters incorporate a screw-thread fitting to attach the diffuser. Some filters have a specially shaped underside to the filter lid which acts as a diffuser, so don’t worry if you don’t have a separate diffuser
  • Normally there is air relief tube extending up through one of the holes in the diffuser - this tube allows pressure to be balanced between the top and bottom halves of the filter - take care not to damage the tube or breather-cap which is fitted to the top of the tube
  • Now you can get at the filter media for removal
  • Wear rubber gloves and use an empty can or plastic jug to scoop out the sand
  • Put the removed sand into a bucket for later dumping
  • Take care not to damage the plumbing inside - feel your way until you are familiar with the layout of components
  • Once most of the media has been removed unscrew the collectors from the central hub of the lateral assembly for inspection and possible later renewal
  • Use a little residual media and water to scour the inside of the filter vessel and then remove the remainder of the media
  • Wash the top and outside of the filter and the screw threads of the collector hub with a hose to remove any grains of media
  • Check, and if necessary change, the 8 or more ‘collectors’ or ‘laterals’ in the lateral assembly, which are fitted like spokes on a central hub at the bottom of the filter; buy them at your local pool-shop but take an old one along with you for comparison because there are several sizesSanmd-filter Lateral Array Collector

A typical collector from the lateral assembly

Replenishing the filter media: -

  • Consider changing the media to Zeoclere-30Zeoclere-30 - it's a little more expensive than Silex but filters much better and last for 10+ years - far longer than Silex, and also strips ammonia and dissolved metals from the pool.
  • There may be an information label, on the outer surface of the filter, which details the filter Make/Model and the quantity of Silex within it
  • Very often this is missing or illegible and you will have to guess how much you need, using the amount  removed as a rough guide
  • Note: ZeoclereZeoclere-30 is approximately 80% the density of sand so you need only 80%-by-weight: - thus if your filter contains 100Kg of Silex you need only 80Kg of Zeoclere to re-fill the filter
  • Place a can or plastic jug over the upward-facing opening to the inlet pipe to avoid filling it with the new media
  • Pour new media into the filter and add water to help it to settle
  • The correct level is to the top of the horizontal section of the upper pipe. (It’s simple once you see the inside of a sand-filter)
  • If you add too much media the level will adjust automatically during routine back-washing, when the excess will be gradually flushed out
  • Rinse any grains of filter media from the filter lid, nuts and caps, or lid screw thread as applicable
  • Examine the filter lid ‘O’ ring and replace if it is damaged in any way
  • Smear the ‘O’ ring with a thin coating of silicon grease or Vaseline and thoroughly clean the underside of the filter lid and the filter seating
  • Fill the filter with water, replace the lid and tighten down carefully
  • Set the Rotary Valve to ‘Backwash’ and open the Bottom Drain and Waste valves
  • Backwash the media for several minutes to remove dust, and then Rinse as normal
  • If you are re-filling with Zeolite you should backwash each bag thoroughly before putting the next bag in - it’s more time-consuming but the results are worth it
  • Check for leaks during the 'Rinse' process and rectify them
  • Repeat the cycle until the water runs clear
  • Set all the Pump-room Valves and switches to ‘Filtration

Congratulations! - you have just renewed the filter media and collectors!  

Now go and rest your back for three days

The old media should not be used for building purposes, in a garden or in a sand-pit 


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Ken Walker - MyPoolGuru©