Do I Need To Backwash My Sand Filter Daily?

One of the most common types of filtration that swimming pool owners opt for is a sand filter. They require minimal maintenance throughout the season and do a good job at keeping your swimming pool crystal clear all year long.

There are a couple of things you need to do to ensure that it is cleaning your pool’s water at optimum performance. This includes making sure your sand is clean by changing it out every 3 to 5 years and backwashing it from time to time while it is in use.

This often brings up the question, should I backwash my sand filter every day? You do not need to backwash your pool daily, instead, it is recommended to only do this about once every week during the regular season. This will ensure the sand stays clean and keeps more of the dirt out of your swimming pool water.


How Often Should Your Backwash Your Pool?

During regular use, backwashing your pool’s sand filter doesn’t need to be done but about once per week, and can even make it a couple of weeks before backwashing if it is being used lightly.

There are some exceptions to this, and most of them are not that common. However, below I will list a few reasons you might find yourself backwashing your filter 2 or more times in a single week.

Backwash Your Pool Now

You probably should consider backwashing your swimming pool if:

  • You have recently vacuumed the bottom of your swimming pool and it was quite dirty. This will clean the bottom of your swimming pool as well as stir up some of the foreign matter on the bottom which will later find its way to your skimmer. Your filter will begin to get full quickly, and it may need a backwash.
  • Low Pressure – If you find that your pool’s return isn’t returning water normally or at a low rate and isn’t as powerful as it should be, a backwash may fix this issue. Once your filter becomes clogged or partially clogged, it will not be able to filter the same amount of water as quickly. This will result in lower rates of water being returned to your return. Likewise, check your skimmer, an unclean skimmer could also be the result of low power through the pool’s return.
  • PSI has increased by 10 – 15 psi – Most, but not all sand filters are equipped with a gauge on the side or top of the filter. This will represent the amount of pressure being pumped through your filter the entire time it is running. After every backwash, check to see what the PSI is. Once it has risen 10 – 15 above what it was after a backwash, it is time to be done.

How Long Should You Backwash Your Pool?

During a backwash, you will lose water from your pool at a fast rate of speed and with the cost associated with refilling your pool, it is best to limit it as much as possible.

There is a fine line that you want to follow in doing a backwash. If you regularly under-backwash your filter (i.e. Don’t run it long enough), you will find you need to backwash sooner and that the pool water is not as clean as it should be.

On the other side, if you always over-backwash, you will continue to have a clean pool and won’t need to backwash as often, but will be wasting water and it will require you to fill your pool with the water hose more often.

So how long should you allow a backwash to run? You typically should run a backwash for 2 to 4 minutes. This is more than enough time for your filter to rid all the caught contaminants from your filter and down the drain.

Fine Tune Your Backwash Length

A good general rule for a backwash time is between 2 and 4 minutes. I can say in most cases after 4 minutes, the backwash should good enough, but how can you tell if you don’t need to utilize the full 4 minutes of this process?

  • Less dirty sand filters will require less time. If your filter was only partially needing backwashed, such as a weekly event you do on a specific day from normal use, it definitely shouldn’t need the full 4 minutes. In fact, the 2-minute mark is most likely good enough in this type of situation.
  • If you vacuumed your pool recently, the pool filter may be closer to capacity. This will likely take a little bit longer for the debris that is in your filter to push through causing your backwash to take a little bit longer than a regularly scheduled backwash maintenance event.
  • Until the water is clear. Most sand filters will have a sight glass on the filter that fills up with water. At the beginning of your backwash, it will turn black, green, or just plain dirty as the dirty water exits the filter. Once the dirty water turns clear, you know the filter is now clean. You can stop the backwash once you notice the clear sight glass. I still recommend 2 full minutes if it does become clear prior to the 2-minute mark for extra measure. However, if you are confident everything is good in 90 seconds, it very well may be good enough for your pool filter.

Always Rinse After Backwashing

Once you have completed your backwash, whether it was routinely scheduled or you had some heavier use than normal, rinsing is necessary before returning your filter back to filtration mode.

This allows the water to rinse the sand that is used in cleaning your pool daily and settling it back down. It finishes removing any leftover dirt and debris from the sand and pipes. Failing to do this simple procedure before turning it back to filtration mode can result in dirt and even sand being pumped briefly into your swimming pool once the pump is turned back on.

How long should you rinse your sand filter after a backwash?

Rinsing the sand, however, doesn’t need the same amount of time to complete as the actual backwashing.

A typical rinse is usually complete in about 30 seconds. When you initially begin the rinse cycle you may notice some dirtiness in the sight glass. Then it will again become clear. After 30 to 45 seconds, turn the pool pump off.

After you have the pump off, return to sand filter to filtration mode and you can begin using your pool normally.

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