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How to Backwash a Pool Filter Properly

Backwashing a Pool Filter in 2020

For anyone that owns a pool, this is just one of the things that must be added to the maintenance and upkeep of an above ground pool. Of course, no one wants to think of all the maintenance involved in owning a pool, but the great thing is that if done on a regular basis, these steps are minimized over time and leave your more time for pure enjoyment swimming with family and friends.

backwashing pool filter

Over time, there is going to be buildup in the sand filter that will affect water flow in your pool. Once you notice this, actions must be taken because this is a sure sign that your pool will not be functioning at its best. This diminished productivity and pressure will compromise the performance of your pool and it will mean that it has come time to clean those contaminates out. This involves backwashing the sand, and this guide will go through the steps involved so that you can backwash a pool filter in the most effective manner.

The majority of people have no idea that the word backwash has an entirely different meaning in the pool world. The meaning is more literal and you should always remember that a pool can only be as clean as the filter it uses. Once you begin to backwash your pool, you will see that it is not always necessary to take each little piece apart and wash every single crevice.

Why You Should Backwash Your Pool

You may want to know why backwashing is important or even necessary and the fact is that if it is not done regularly, your pool will be compromised to the point of being almost impossible to swim in. The reason is that when you swim, there are oils, debris, dirt, and grime left behind that are collected at the filter medium. As time goes on, the filter medium becomes clogged and the efficiency is then less than stellar. Backwashing the pool involves sending the water back through the filter, then out the drain port. This dislodges the debris located in the filter to make it easier to move and thus restoring the pool to a functioning level. The best way to describe it is to compare it to the strainer you use in your kitchen to catch small tiny particles of food. Backwashing protocols vary just a bit depending on the pool filter type used.

Backwashing a Sand Filter

This process is not nearly as messy as you think it may be, partially because you only need one item to get started and the sand actually never vacates the filter. Simply get a backwash hose and go from there.

Backwashing with Multiport Valves

This process is also fairly direct:

  • attach backwash hose to backwash port
  • turn off the filter system
  • turn on the multiport valve to the Backwash setting
  • turn filter system on again
  • allow water to run out of backwash port and through backwash hose for approximately a minute
  • turn off the filter system
  • adjust the multiport valve to Rinse
  • turn on the filter system
  • adjust the multiport valve to Filter

note: you never want to handle the multiport valve when the pool filter is activated and flowing. Doing so could result in breakage which can lead to water leakage.

Backwashing the D.E. Filter

Before you get started, you are going to need the following items:

  • backwash hose
  • D.E. powder
  • 1-pound of D.E. scoop (or 1-pound coffee can)

D.E. powder, also known as diatomaceous earth powder, is the white powder that you add to filters that attaches to grids and forms a D.E. ‘cake’ that filters out those fine particles.

Backwashing Using a Multiport Valve

You will need a bit of time to do this, and don’t be surprised if it takes the entire day. The process is as follows:


  • turn off filter system
  • connect hose to waste port
  • activate valve to Backwashing
  • turn filter system on and then allow the unit to run for approximately 2 minutes
  • turn filter off
  • adjust vale to Rinse
  • turn system off
  • adjust valve back to Filter setting
  • add D.E. powder

Backwashing a Push/Pull Valve System

There is a slight variation on this process, and it includes:

  • turn system off
  • connect hose to backwash port
  • open backwash gate
  • turn the system back on and allow to run for approximately 3 minutes
  • turn system off
  • close push-pull valves , the next steps involve the following:
  • add D.E. to the filter
  • refer to manual to know how much powder to add
  • prime pool pump
  • remove lid of strainer basket
  • fill the basket with, making sure it is enough for it to run through the incoming line
  • turn on pool pump
  • mix right amount of D.E. powder to create a creamy solution
  • ensure pump is still running
  • pour creamy solution into pool skimmer

Note that the pool pump should be running for at least half an hour so that the D.E. will be able to be distributed evenly over filter grids.

When Should You Backwash the Pool?

Once the filter is first set up, it is important to note the pressure gauge to ensure that it is of normal operating pressure. Over time, the pressure will begin building when water is not flowing freely through it. The time to backwash is when the gauge is at 10psi above the normal operating levels. If it gets up to as high as 10psi over the normal levels, you are already well past the time to get to the action.

It is not recommended to wait until it reaches that mark, however, and if anything, know that the filter always works better when it doesn’t have clogging issues. You will probably always have a bit of debris and grime there, but those tiny bits actually help to keep others from getting through the system, So the best time to clean that filter is why it is only slightly dirty.

Disposing of Water from a Filter Backwashing

Each time that you backwash, you are going to be removing gallons upon gallons upon gallons of water from the pool. So, the question is this: where is this water going to go eventually? There are a few options: the yard, the street, to a nearby creek or river?

Since none of these is exactly the best option as the treated water can damage plants, groundwater, and buildings, you need other options on the table. But, you are going to have to remove it in a way that is safe for you, your neighbors, and doesn’t lead to any fines. Above all else, you want to keep the environment safe and free of any damage. The following are some options that you can choose from:

Storm Drain

There are some cities that allow water to flow into storm drains. If you live in a city that allows this, this may be the best route to go. Check beforehand, however, as it may require a permit from the local city government. Before using a storm drain, you might have to eliminate the salt levels or chemicals in the water so that it adheres to community rules. Again, check with your local government for the regulations on proper disposal.

Plumbing Cleanout

If your home has a plumbing cleanout, this may be another option that you can utilize. Again, you will have to check with local authorities as you may require a permit to use this method for removal. There are few places that will let you release your pool water into the septic tank as this can affect the tank in an adverse way. Septic systems already have active enzymes in them that are used to dispose of waste and if you place even more chemicals on top of those, you very well could end up with an even bigger mess than you began with.

Dry Well

If you have access to a dry well, this could be the best bet for you since they are able to dispose of pool water in a sensible way that won’t damage any adjacent property or plant life. By using a dry well, you can get rid of pool water and not have to worry about your neighbors or any other problems that could arise because of this method.

No matter how much water manages to pass through, you won’t have a problem using a dry well since it is not flowing back into other water sources, so any damage that could occur with other methods is a foregone conclusion. Aside from getting permission for using a dry well, remember that they must be built by a professional and construction could cost thousands of dollars. If you have a pool, however, these costs will balance out long-term.


The process of backwashing a pool filter has many steps, but it is not too difficult. Once you have done it a few times, it will become routine and you will find it safer and affordable over time. If you have any questions, you can always count on your local water officials to assist you.

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