We all know what “backwash” is and that’s gross. When it comes to your pool filter, however, the term “backwashing” is actually a good (and sanitary) thing to do.

If your pool uses a sand or D.E. filter then backwashing is the name of the game for keeping your pool water uncontaminated by debris, your pool filter clean, and actually extending the life of your filter in the process.

What is Backwashing?

Backwashing is like a flush or detox cleanse for your pool filter.

Your pool filter is what keeps your pool water clean and free of debris so that you and your family can swim everyday carefree. But as your pool filter works, it’s constantly being bombarded by dirt, oils, and other nastiness that it’s drawing out of your pool water.

So what happens when your pool filter gets overloaded with dirt and grim? That’s when backwashing comes in. Just as you periodically change the air filters in your air conditioning unit, your pool filter needs a bit of TLC every once in a while.

If you have a sand or D.E. pool filter, however, changing a filter is not part of the deal. Rather than spending money on new filters, you simply have to rinse out the buildup, saving you money in the long run. Backwashing your pool filter is a process that cleans the gunk out of your pool filter to keep your system running at its best.

When It’s Time to Backwash

How often does it make sense to backwash your sand or D.E. pool filter? 

You have a busy life and pool maintenance already may seem like a chore, so spending a day backwashing your pool filter more often than necessary is not a good use of your time. 

When you install a sand or D.E. pool filter, make sure to take note of the initial pressure reading that you see. This is the starting or normal pressure that means everything is free and clear. As that pressure starts increasing, you know that the filter is doing its job and is collecting all of the debris that you really don’t want floating around in your pool water.

Since everyone’s pool, backyard, and swimming habits are different, there’s no set time for checking or backwashing your filter. It’s all going to depend on the pressure reading, which shows how much buildup is sitting in that filter.

If you set a reminder to periodically glance at your filter’s pressure gauge, you can keep an eye on how quickly the pressure reading climbs. When it gets to 10 psi over the normal (starting) mark, you know it’s time to backwash your system.

Although it might seem counterintuitive, you actually don’t want to clean your filter before it reaches the point of 10 psi (over normal) reading. Your filter will function better when it has some residue in it to give it texture. Debris in your filter acts as a filter booster and helps to filter more waste out of your pool.

How to Backwash Your Sand Filter (Step-by-Step)

Don’t worry, you won’t have to remove the sand from your sand filter and wash each grain by hand. In fact with this process, the sand actually never leaves the filter! And to make things even better, you only need one thing to get the job done: a backwash hose. 

Backwashing with a Multiport Valve

A sand filter featuring a multiport valve is actually one of the simplest filters to clean. This is a super straightforward process that you can get done in no time at all. 

  1. Attach the backwash hose to the waste or backwash port.
  2. Turn the filter system off.
  3. Turn the multiport valve to the “Backwash” setting.
  4. Turn the filter system back on.
  5. Let the water run out of the backwash port and through the backwash hose for about a minute, or until the water runs clear.
  6. Turn the filter system off.
  7. Turn the multiport valve to the “Rinse” setting.
  8. Turn the filter system back on.
  9. Rinse the filter for about 30 seconds.
  10. Turn the filter system off.
  11. Turn the multiport valve to Filter.

Pro Tip: There’s a lot of turning your system on and off in this process but it’s important to never change the setting while the pool filter is on and running. This could loosen or break the rubber gasket, which can cause water leakage and all kinds of problems in the future.

How to Backwash Your D.E. Filter (Step-by-Step)

Wait, what is a D.E. filter anyway? For the pool filter newbies out there, let’s clear up the confusion before we clear out the gunk.

What is a D.E. Filter?

D.E. stands for “Diatomaceous Earth” which is a super weird (but also cool) name for a white powdery sedimentary rock made of fossilized single-celled organisms called diatoms.

This fine powder is added to a filter and forms a D.E. “cake” on the grids inside. This substance is frequently used as a filtration aid and is especially good at filtering out very small particles from water.

So now that we know what we’re working with, we can get started on the fun part. Take a minute to collect your supplies before you get started. If you don’t have a D.E. scoop on-hand, you can always use a one-pound container from your kitchen or garage.

What You Need

  • Backwash hose
  • Diatomaceous earth powder
  • One-pound D.E. scoop

The amount of D.E. powder that you’ll need will vary depending on what size filter you have. Make sure to read the manufacturer’s instructions thoroughly to determine how much you’ll need.

Backwashing with a Push/Pull Valve

  1. Turn off your filter.
  2. Connect the backwash hose to the filter’s port.
  3. Open the backwash gate.
  4. Turn your filter back on and let it run for about three minutes. You’ll see the pool water start to flow out of the backwash port.
  5. Turn your filter system off again.
  6. Close the push/pull valve.
  7. Add D.E. powder to the filter.
    • Check the manufacturer’s instructions to determine how much D.E. powder you’ll need to add.
    • Prime the pool pump.
    • Remove the strainer basket lid.
    • Fill the basket with water, and allow some water to run through the incoming line.
    • Turn on the pool pump.
    • Mix the correct quantity of D.E powder with enough water to make a semi-liquid batter called “slurry”.
    • Double-check that the pump is running.
    • Pour the slurry directly into the pool skimmer.
  8. Run the pool pump for at least 30 minutes to allow the D.E. to distribute evenly over the filter grids.

Backwashing with a Multiport Valve

  1. Turn off the filter system.
  2. Connect the backwash hose to the filter’s waste port.
  3. Turn the multiport valve to Backwash. If you have a push/pull valve, open the backwash gate.
  4. Turn the filter system back on, and let it run for about two minutes. This will allow pool water to flow out of the backwash valve or port.
  5. Turn the filter system off.
  6. Turn the multiport valve to Rinse, turn the system back on, and let it run for about another minute.
  7. Turn the filter system off.
  8. Turn the multiport valve back to Filter.
  9. Add the correct amount of D.E. powder to the filter.
    • Refer to your filter owner’s manual to determine how much D.E. powder you’ll need to add.
    • Prime the pool pump.
    • Remove the strainer basket lid.
    • Fill the basket with water, and allow some water to run through the incoming line.
    • Turn on the pool pump.
    • Mix the appropriate amount of D.E powder with enough water to make a slurry, which is a thin, creamy solution.
    • Make sure the pump is running.
    • Pour the slurry directly into the pool skimmer.
  10. Run the pool pump for at least 30 minutes to allow the D.E. to distribute evenly over the filter grids.

Pro Tip: There’s a lot of turning your system on and off in this process but it’s important to never change the setting while the pool filter is on and running. This could loosen or break the rubber gasket, which can cause water leakage and all kinds of problems in the future.

Getting Rid of the Waste

Whenever you backwash your filter, the wastewater is going to have to go somewhere. Even though it doesn’t seem like much, it could actually be hundreds of gallons of water that are pulled from your pool and need to have somewhere to go. 

So, what are the best options for getting rid of backwashing waste?

Sewer Cleanouts

If you’re not familiar with the term, a sewer cleanout is a place where your home’s sewer line can be accessed for cleaning. In most cases, this is to prevent sewage backups. These can usually be found near the sidewalks in front of your house or near the home’s foundation.

Make sure to check with your local water/sewer authority to determine if there are any regulations regarding disposing of waste in this way or if you need to treat the water before dumping.

Pro Tip: Never dispose of backwashing waste in a septic system. Doing so will kill all of the enzymes in the tank that are necessary for the breakdown of other types of waste.

Storm Drains

Every locality will have its own rules and regulations about if and when storm drains can be used to dispose of pool water. For some, it may be as simple as applying for a permit first. For others, you may need to dilute the water to lower the chemical and salt content.

Either way, it’s important to check with your local water company to find out the lowdown before you start dumping.

Other Ideas

If neither of these options works for you, you can always get in touch with the water authority that governs your area. They will be able to tell you what your particular region allows and what steps you need to take before backwashing.

Locate your regional watershed for more information on methods, permits, and treatment requirements.

Backwash to the Rescue!

Backwashing your pool filter will help to keep your pool cleaner, your filter functional for a longer time, and will save you a ton of money in the long run. Now that you’re a backwashing expert, get out there and go crazy!