What Is Backwashing And What Is Its Purpose?

As a swimming pool owner, there are a number of different maintenance tasks to keep your swimming pool clean and functional. One important maintenance task that helps keep your swimming pool’s filter system in working order is backwashing.

Sand Filter Tank SystemWhat is backwashing and why is it important?

Putting it simply, backwashing is cleaning the filter by reversing the flow of water to remove any debris, build-up, and contaminants.

When should I backwash my pool filter system?

How regularly you need to backwash your filter really depends on how often you use your pool and how dirty it gets throughout the swimming season. Generally, you’ll want to backwash about once a week. As dirt accumulates in the swimming pool filter bed, resistance to flow increases, which causes a reduction in water discharge to the pool. When the flow is insufficient for proper water circulation, or when the pressure gage indicates a pressure rise of 8-10 pounds above the clean pressure, it’s probably time to clean your pool filter.

Another necessary time to backwash your pool water is after killing algae blooms or when treating cloudy water. You should wait to add chemicals to your pool until after you’ve backwashed as the process will dispose of some existing water in the pool.

How to backwash a sand filter

The correct backwash rate for a high-rate sand filter is the same as it was when the pool filter was in the “filter cycle” (15-25 gpm per square foot of the filter area). In rapid-rate sand filters the backwash rate must be between 12-15 gpm per square foot of filter area (which is 4-5 times greater than the average filter rate per square foot).

Step by step instructions on how to backwash a sand filter:

  1. Turn off the pump. Never change the filter control valves with the pump running.
  2. Turn the control valve to the “backwash” position.
  3. Turn the pump on and allow it to run until the effluent water is clear as seen in the sight glass at the backwash valve or waste piping. This usually takes between 2-4 minutes.
  4. Shut off the pump and turn the control valve to the “rinse” position.
  5. Turn the pump on for 20-30 seconds. This resets the sand bed and sends any residue of dirt into the waste line rather than into your pool.
  6. Shut off the pump again and return the valve back to the “filter” position. Turning the pump back on resumes the filter cycle.

Backwashing your filter is a routine and simple process that’s essential for the health and functionality of your pool. If you follow the below steps along with other ongoing swimming pool maintenance, you can help keep your filter working as efficiently as possible!

If you have any further questions, please refer to the manufacturer’s guide or manual that came with your filter system.

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One response to “What Is Backwashing And What Is Its Purpose?”

  1. Paulette Porter says:

    Knowledgeable learning things I didn’t know

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