Read on to find out exactly what backwashing is, how often you should backwash and how to do it.

What is backwashing?

Backwashing is a pool term used to describe a filter cleaning method which reverses the flow of water through your filter system. While most pool filters help to remove organic material by pushing water through a porous medium (typically sand) and returning the clean water to the pool, over time larger particles build up in the filter. This can reduce the efficacy of your filter due to an increase in pressure and even lead to damage.

The process of backwashing dislodges trapped debris and contaminants, flushing them out through your value’s waste line or a hose that is connected to the pool pump. When the filter media is clean, the pressure gauge is lower and water can easily flow in and out of the system.

How often should you backwash your pool?

The frequency of backwashing depends largely on how much use your swimming pool gets and the type of filtration system as well as its position. If your pool is surrounded by shrubs or trees, its likely to need more regular backwashing than a pool that isn’t subjected to leaf little and organic debris.

As a general rule, you should be backwashing your pool about once a week or in conjugation with your scheduled maintenance. Another industry standard is to backwash when your filter’s pressure gauge reads 8-10 PSI (pounds per square inch) over the starting level or “clean” pressure. For example, if your filter is running normally at 15 PSI but increases to 25 PST, you should perform a backwash.

You should also consider backwashing after a major storm or an algae outbreak in your area. If you have deciduous trees nearby, it may also be worth scheduling a backwash after all the foliage has dropped.

If you have a diatomaceous earth (DE) filter system, it will need to be torn down and cleaned at a minimum of six times per year. A sand filter is torn down twice a year and can be backwashed monthly.

DIY pool cleaning or engage a pool cleaning professional? Consider these factors before you make a decision.

When you shouldn’t backwash

Backwashing Pool 02
Image source: Flickr Brett Samuel

  1. Backwashing is a great way to clean out clogged filters but there are times you should avoid the process.
  2. If your pool has or had an algae issue is it recommended to by-pass your filter entirely and vacuum directly to waste. This is because live algae are able to easily pass through your filter medium and re-enter your pool.
  3. It’s also advised you vacuum directly to the water and down the drain if your pool has been exposed to an unusually high level of debris or dirt. For example, if a neighbour is building nearby or there are roadworks in the surrounding streets.
  4. How to backwash a pool’s filter
  5. Backwashing is a process you can easily do yourself or engage the services of a pool maintenance team.
  6. If you’re wanting to backwash a sand filter yourself, here are the steps you should follow:
  7. Turn off your pool’s pump and filtration system.
  8. Clamp the backwash hose to your water outlet.
  9. Set the filter value to BACKWASH and ensure the handle locks in place. You’ll see water flow through those the hose or equipment in the view glass.
  10. Wait for a few minutes until the water runs clear.
  11. Turn off the pump to cease the backwashing.
  12. Turn the filter valve handle to RINSE and ensure the handle locks in place.
  13. Allow the rinse process to occur for 1 minute or until the water is clear.
  14. Turn off the pump.
  15. To prevent water from entering the filter from your pool, close the skimmer valve.
  16. Empty and clean the skimmer basket and hair catcher. Then position back in their place.
  17. Open the skimmer values and reset the Filter Valve to Filter. Ensure the handle locks in place and turn the pump back on.

To backwash a DE filter, follow these steps:

  1. Turn off your pool’s pump and filtration system.
  2. Set the filter value to BACKWASH and ensure the handle locks in place. Turn the pump on and you’ll see water flow through the view glass.
  3. Wait until the filter view glass is clear.
  4. You can alternate between backwash and rinse a few times to remove the DE. Remember to turn off the pump when changing the value settings when doing this.
  5. DE can be discarded in the trash.
  6. Disassemble the filter while the pump is turned off. You may need to change the timer settings to do this.
  7. Open the release valve and drain the filter. To remove the water more thoroughly, remove the drain plug from the bottom of the filter. The water will drain from the bottom of the tank.

Backwashing tips

  • Make sure your pup is always turned off when running a backwash or resetting the filter valve. If you forget to, you may cause damage to your system or possibly destroy it which will turn out to be a costly mistake.
  • Backwashing can result in a loss of water. While this is unavoidable, you can minimize the amount of water you lose by not overdoing the backwashing process. Keep a close eye on the colour of the water through the view glass and stop the minute it becomes clear.
  • During the backwash, you’ll also inevitably wash out some of your sand along with the debris and dirt. This will require you to top up the amount of sand in the filter. To minimize the amount of sand blowback into your swimming pool, run the filter system on the rinse setting for a minute when you do the top up.
  • In the even your backwash valve is becoming too difficult to turn, it is recommended you do a teardown and lubricate the valve before any leaks occur.
  • When reassembling your filter system after backwashing, examine all your parts including the cartridges, grids and laterals. Don’t rush the reassembly as most filter leaks are caused during this time.