29th May 2015

Choosing the Best Filter for Your Swimming Pool

Which Swimming Pool Filter?

There are in essence, only three basic types of swimming pool filter to choose from.... but they're all frustratingly similar and have unique pros and cons, leaving you scratching your head over which to choose. Here are the basics:


The original pool filter- cartridges -have been doing their thing since the 70s. Cartridge swimming pool filters work by passing water through a large piece of paper or plastic based material, much like a sieve to catch any debris.

Cartridge filters occasionally block up in the same way other filters do, but due to their greater surface area, occupy far less floor space. Cartridge filters do not require backwashing either. They are removed and replaced with a new filter, or manually washed out by hand. Other advantages' of a cartridge filter, is that they take less room, they don't need backwashing or any connection to the mains drainage system, which can be problematic in terms of available flow and invert levels. The disadvantages however, are that the cleaning process can be quite a messy affair. The detritus cannot be washed down the drains, as it will block them very quickly, so it has to be disposed of to a regulated waste site.


Silica sand is the cheapest, most common and easiest to replace material used for swimming pool filters, making it a hit with many swimming pool owners. Sand is inert and in theory the simplest most reliable filter media.

Water is filtered through the sand which catches any debris and dirt, eventually increasing the pressure and lowering the water flow. At this point, the sand will need cleaning, or backwashing. Backwashing is a reversal of the water flow through the filter vessel. The backwash flow rate is designed to fluidise the sand bed and releases any suspended debris particles which are then washed away to drain. When this process is carried out correctly, the filter returns to a fully cleaned state. Backwashing is a simple 5min process involving changing valve positions.

If you're worried about having to change the sand often, fear not. There is no reason to replace sand itself, as long as the backwash process has been carried out effectively over the filter life. The most common reason for needing to replace sand is that it has become compacted or mud balled. This is due to either poor maintenance, or backwashing at the incorrect rate.

Tips for Choosing a Swimming Pool Filter

  • If you want something cheap, strong and durable, choose sand.
  • To give your pool filter a hand with the cleaning, try adding a chemical flocculant (with great care and at the correct filtration rates) to the water. It clumps small particles of debris together, making it easier for the filter to collect.
  • Whatever filter you opt for, make sure it's regularly cleaned and maintained by professional swimming pool maintenance providers and you'll have a healthy and happy swimming pool all year round.

Get in touch to schedule a bespoke swimming pool maintenance service from Guncast.

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