Pool sand filters: their benefits and how to maintain them

Backwashing sand filters and our tips for optimum filtration

Pool sand filters are considered the easiest to use and are a popular choice amongst the other varieties. Pool water is pumped through the system and the sand in the filter catches any dirt and debris, purifying and cleaning the water before returning it to the pool. Although the operation of a sand filter is basic, it is incredibly effective. The sand used within the filter is specially graded to ensure it traps tiny particles of dirt, debris, and bacteria; the more tightly packed the sand is within the filter, the more efficient it becomes. This sand is often referred to as pool sand, however, your pool filter manual may refer to it as 16/30 or 16-30 sand.

Some of the benefits of using sand filtration for your pool filter are:

  • It’s an easy to use system
  • Requires low maintenance that doesn’t require a service call
  • Removes small and large dirt and debris from the pool
  • Is relatively inexpensive to install and update

You might now be wondering what is involved with maintaining a pool sand filter. There is a simple process called “backwashing” which removes any dirt, algae, and visible debris from your sand filter by reversing the flow of water and expelling the dirty water into a drain. By performing a backwash process periodically, you will keep the sand filter operating at its optimum performing level.

How often do we mean by periodically? A general rule is to backwash once the pressure displayed on the pressure gauge is 8-10psi over the starting level and just after you have vacuumed the pool. If your pressure gauge has a red and green zone, you want to be backwashing when the needle is within or close to the red zone. It is also a good idea to check what your pool filter manual says regarding signals for when your filter needs backwashing.

If you think the sand in your filter requires replacing, we recommend consulting your pool filter manual for guidance on timing and requirements first. Once you have this information, it will make conversations with pool shops or sand suppliers, like River Sands, easier and quicker. A general rule for replacing the sand is every 6-7 years depending on the level of use of the pool.

General steps to backwash your pool sand filter:

  1. Turn off your pool pump
  2. Set the sand filter multi-port valve handle to the backwash position and ensure the handle locks in place
  3. Turn on the pump and allow the sand filter to backwash for 2-3 minutes or until the water in the sight glass is visibly clear
  4. Turn off your pool pump
  5. Set the sand filter multi-port valve handle to the rinse position and ensure the handle locks in place
  6. Turn on the pump and run the rinse process for 1-2 minutes or again until the water in the sight glass is visibly clear
  7. Turn off your pool pump
  8. Return the sand filter multi-port valve handle to filter and ensure the handle locks into place
  9. Turn on the pump and continue to run under normal operating conditions.

It’s also important to know when not to backwash your pool sand filter. This primarily is when the pool contains an unusually high amount of dirt or debris and it is advised to by-pass the filter entirely by vacuuming directly to the waste setting. Another time when it’s best not to backwash is if the water has or has had an algae problem. Algae, both dead and alive, can easily pass through the filter sand and re-enter the pool. Again, it is advised instead of backwashing, to vacuum the pool water directly to the waste setting and down the drain.

Extra tips on backwashing a sand filter to ensure optimum filtration:

  • It’s unavoidable to lose water while backwashing, however, to ensure you don’t flush out more water than necessary keep a watchful eye on the colour and quality of the water in the sight glass.
  • Backwashing will inevitably wash out some of the sand from the filter along with the dirt and debris. When you notice a drop in the amount of sand in the filter, it is necessary to top up the sand level and run a rinse cycle to reduce the amount of sand blowback into the pool.
  • It is possible to backwash too much and for too long. Excessively backwashing can reduce the sand filter’s efficiency.
  • Always make sure to turn off the pool pump between the different steps that involve resetting or moving the filter valve setting. If you don’t turn the pump off, there is the possibility of causing damage to the system.
  • It’s important to include the rinse cycle in the backwashing process, as the rinse setting reseats the sand into its original position for optimum filtration.
  • Maintaining your pool water chemistry is crucial to kill the tiny bacteria which can slip through the sand filter.

If you have any trouble with your pool sand filter, it is always best to check the pool filter manual first and then reach out to your local pool store for help.