How To Backwash a Pool Filter

There are various filter types on the market, but they all serve the same purpose: to rid your pool of debris, bacteria, and algae. Because of all the work they do in preventing water-borne diseases, they need help keeping your water quality in tip-top condition.

Backwashing is one of the most convenient and affordable ways to ensure your filter works as it should. After all, what goes in must come out. Once in a while, you have to take out all the tiny contaminants that the filter sucks from your pool.

Once you learn how to backwash like a pro, you won’t always have to dismantle your filter and clean every little crevice. Read on to learn everything you need to know about backwashing a pool filter.

What Does Backwashing Mean?

No matter what filter you use, it’s best to keep it clean to maintain your pool’s water quality through backwashing.

It may sound like a complicated procedure, but it’s not. In reality, it’s a method to thoroughly clean a pool’s filter without having to do it manually. The best part is, it only takes a few minutes of your time.

When you backwash your filter, you reverse the water flow, moving it back toward the waste line. It’s an ideal alternative when cleaning and teardown are not practical solutions.

Why Should You Backwash Your Filter?

There are various ways to wash the apparatus, but why is backwashing ideal?

As water goes through your diatomaceous earth (D.E.) or sand filter, it leaves behind pollutants like dirt and oil. When your filter gets clogged, it becomes less effective.

Backwashing your pool involves sending water backward through your filter and toward a drain port. This pressure forces the debris out, enabling you to remove it and quickly restore the filter’s functionalities.

Think of your pool’s filter like a vacuum cleaner or a water purifying system. As it performs its cleaning functions, it collects unwanted particles in the process. When it gets full, your pool becomes murky and encourages algae growth. For these reasons, keeping your filter clean is an essential step in maintaining your pool.

Regardless of your pool filter type or brand, backwashing typically works the same way. The procedures may vary, but the results are always worth it.

When Should You Backwash?

As a general rule, it’s best to backwash your pool weekly or in time with your scheduled maintenance. However, there are other indicators to watch out for, like the ones listed below.

PSI Increase

Pool filters often have a pressure gauge. When you first install yours, take note of that number for benchmarking purposes. As you use your filter, the PSI or pounds per square inch figure will increase. The more contaminants you trap in your machine, the higher your PSI becomes.

Any time your pressure gauge goes 8 to 10 PSI points over your usual level, take it as a sign to backwash your filter. For instance, if your filter usually operates at 10 PSI, and you see it rise to 20 PSI, it’s time for a backwash.

High Water Levels

Some factors increase pool water levels, like heavy rain, underground water leaks, and human error. When water levels get too high, your skimmers can’t suction floating debris, leaving your sanitizer exhausted and your swim less safe.

When your water level goes beyond one-half of your skimmer, it’s best to perform a backwash immediately. If you don’t act fast, you risk overflow, compromised surface circulation, and permanent damage to your pool.

Cloudy Water

Cloudy pool water may indicate various concerns, including a clogged filter, improper chlorine levels, or the start of algae formation. No matter the cause, backwashing your pool can bring back its usual crystal clear appearance.

How Do You Backwash Your Pool Filter?

There are three pool filter types: D.E., sand, and cartridge. However, backwashing is not possible for cartridge filters because they don’t have the valves for the process. This section will discuss how to backwash D.E. and sand filters.

Backwashing D.E. Filters

Before you begin backwashing, you need the following supplies:

• A backwash hose
• E. powder
• A one-pound D.E. scoop

What Is Diatomaceous Earth?

D.E. is an organic insecticide made of fossilized skeletons of diatoms — one-celled microalgae found in oceans. Once you add the powder to the filter, it attaches itself to the crevices and clumps into a cakey substance. This material can filter out even the smallest contaminants.

How Much D.E. Powder Should I Use?

The amount of powder you need depends on your filter size, so it’s best to revisit your owner’s manual for this information.

If you can’t find details from your guidebook, you can use one scoop of powder for every ten square feet of a new filter. For backwashing purposes, use 80% of this amount. You always measure D.E. powder in pounds, so use a one-pound D.E. scoop for accuracy.

For instance, it’s best to use five pounds of D.E. powder to clean a new filter. However, for backwashing purposes, you can reduce it to four scoops.

How Do You Clean a D.E. Filter With a Multiport Valve?

When it’s time to backwash your pool, follow the instructions below:

1. Turn off your pool’s filter.
2. Connect the backwash hose to the waste port.
3. Switch the multiport valve to Backwash.
4. Turn your filter back on and run it for two minutes to reverse the flow of the water.
5. Turn your filter system off again.
6. Switch your valve to Rinse, turn your filter on, and run it for a minute.
7. Again, turn your filter off.
8. Switch the valve back to Filter.
9. Add D.E. powder to the filter, and make sure to get the amount just right.

• Prime your pool pump.
• Take off the strainer lid.
• Fill the basket with water and let the water run through it.
• Turn on your pump.
• Mix the D.E. powder with water to create a cakey substance.
• Pour the mixture into the pool skimmer.
• Run the pump for at least 30 minutes to distribute the solution evenly.

Note: Do not turn the valve handle while your pool filter is running. Doing so can break its rubber gasket, which will cause leakage out of the wrong ports.

How Do You Clean a D.E. Filter With a Push/Pull Valve?

There are minor differences between using a multiport and a push/pull valve. Follow the instructions below when using the latter:

1. Once you’ve turned off the filter system and connected the hose to the backwash port, open the backwash gate.
2. Afterward, turn your filter back on and run it for three minutes to let water flow out of the port.
3. Turn your filter system off again.
4. Close the push/pull valve.
5. Add D.E. powder to your filter. Refer to the guide in the multiport valve section.

Backwashing Sand Filters

Can you imagine having to remove sand from your filter and washing it manually? It would be a tedious and potentially messy process. However, when you learn how to backwash sand filters, you won’t have to go through this almost impossible feat.

Cleaning sand filters is much faster than washing a D.E. one. You only need a backwash hose to get started.

How Do You Clean a Sand Filter With a Multiport Valve?

Unlike cleaning D.E. filters, this procedure is a straightforward one.

1. Connect the backwash hose to the waste port.
2. Turn off your filter.
3. Switch the multiport valve to Backwash.
4. Turn your filter system on again.
5. Let the water course through the backwash port for one minute or until the water runs clear.
6. Turn your filter off again.
7. Switch the valve to Rinse.
8. Turn your filter back on.
9. Rinse your valve for about 30 seconds.
10. Turn off your filter.
11. Switch the multiport valve to Filter.

Note: Do not turn the valve handle while your pool filter is running. Doing so can break its rubber gasket, which will cause leakage out of the wrong ports.

How Do You Dispose of Backwash Water?

If you’re not sure where to put the end of your backwashing hose, you’re not alone. However, releasing dirty water on your yard, street, or a nearby creek is not a good idea — and may be illegal depending on where you live.

Remember, your pool contains chemicals that can harm plants, animals, and groundwater. Backwashing can pull hundreds of gallons of potential pollutants.

If you want to keep your community safe and avoid hefty fines, here are some areas where you can dispose of filter backwash water:

Sanitary Sewers

In most cases, local authorities recommend collecting, containing, and discharging backwash water into sanitary sewers. Note that they are different from storm drains and septic systems.

However, these regulations depend on where you reside. Before pointing your hose toward a vegetated area, it’s best to check your city’s rules first.

Storm Drains

Some cities allow residents to release backwash water into storm drains. However, in most cases, doing so requires a permit and reducing chemical or salt levels. To avoid hefty fines, contact your local water authority first.

Plumbing Cleanouts

If your local regulations allow, dispose of backwash water through your home’s plumbing cleanouts. Again, you might need a permit to do so.

Make Backwashing a Habit

Backwashing your pool is one of the simplest and most affordable ways to keep your pool water crystal clear and your filtration system in peak condition. You only need a few minutes of backwashing per week to achieve your pool goals.

When you learn this skill, you won’t have to keep spending for specialists to do it, saving you a lot of money. Now that you know how to backwash like a pro, include it in your list of pool cleaning habits.