How to Backwash a Pool: Simple Tricks Pool Pros Don't Share

Proper pool backwashing takes just a few minutes and saves hours of frustration. Many pool owners face cloudy water and poor filter performance because they skip this significant maintenance step. Furthermore, pool backwashing reverses water flow through your filter and cleans out trapped contaminants. Additionally, many people feel unsure about the timing and duration of pool backwashing. Sand filters need backwashing monthly. Also, DE filters require it roughly 6 times yearly. The process helps maintain balanced pH levels, prevents algae growth, and protects against waterborne illnesses.

Your pool filter needs backwashing when the pressure gage shows 8-10 psi above normal operating levels. Therefore, this simple task keeps water crystal clear and extends your filtration system's life. The quickest way to clean your pool filter is through proper backwashing and works better than manual cleaning methods.

Professionals rarely share the best backwashing techniques. Let's maintain your filter with perfect timing and flawless execution.

Backwashing is the life-blood of pool maintenance and works quite differently from regular cleaning. The process reverses water flow through your filter system to flush out accumulated dirt and debris. The science behind this process is simple yet clever.

What is backwashing a pool filter?

Your pool's filtration system needs a good cleaning method that we call backwashing. The process reverses the normal water flow through your filter media instead of pushing it into your pool. This reversed flow carries trapped contaminants out through a dedicated waste line. Both sand and diatomaceous earth (D.E.) filters use this technique, though each type needs a slightly different approach.

How backwashing works in pool filters

Your pool pump normally pushes water through the filter media (sand or D.E.) to trap debris and contaminants before sending clean water back to your pool. These particles accumulate over time and create more resistance to water flow. The process starts by switching the multiport valve to the "backwash" setting, which changes this flow direction. Water then lifts the filter media and carries trapped debris out through the waste port.

The backwashing process should continue until clear water runs through the waste line, that indicates most contaminants are gone. Most systems need a rinse cycle afterward to get the filter media back in its proper position.

Benefits of regular backwashing

Regular backwashing provides several important benefits:

• Clearer water by stopping debris recirculation
• Longer filter life with reduced system strain
• Better pH balance that helps prevent algae growth
• Easier pool maintenance compared to manual filter cleaning
• Better water circulation throughout your pool

The filter pressure should not rise too high, and backwashing prevents this issue. Your pressure gage reading 8-10 PSI above normal operating pressure means it's time to backwash. Poor water flow can reduce circulation and filtration efficiency if left unchecked.

A slightly dirty filter can actually work better than a completely clean one. Small debris particles help catch other contaminants. That's why experts suggest waiting until pressure increases before starting the backwash process.

You need to know the right time to backwash your pool filter. This keeps your water crystal clear and saves you from doing unnecessary work. Let me share some key signs that help create the perfect maintenance schedule.

Using the pressure gage as a guide

Your pressure gage tells you exactly when to backwash. Start by recording the "clean" pressure reading after a new filter installation or complete backwash. The baseline usually sits between 8-20 PSI, based on your setup. You should backwash once pressure climbs 8-10 PSI above this baseline. To cite an instance, see a clean pressure of 15 PSI means you'll need to backwash at 23-25 PSI.

Pool experts suggest you wait until pressure rises at least 5 PSI before backwashing. A slightly dirty filter actually catches particles better than a completely clean one.

Signs your filter needs backwashing

The pressure gage gives you the most reliable signal, but other clear signs tell you it's time to backwash:

1. Diminished water flow - Your return jets show weak circulation that points to clogged filter media
2. Cloudy water - Particles stay suspended because of poor filtration
3. High water levels - This happens especially after heavy rain

You should backwash right away after major storms, algae problems, or heavy swimming activity, whatever the pressure readings show.

How long to backwash a pool

The whole ordeal takes about 5-7 minutes. Run your backwash cycle for 2-3 minutes until the sight glass shows clear water. Switch to rinse mode for 1-2 minutes afterward to properly reset the filter media.

Sand filters usually need monthly backwashing, while DE filters need this done about six times per year. The actual schedule changes based on pool use, environment, and debris amounts. Under normal conditions, a properly sized sand filter should run about 4 weeks between backwashes.

The backwashing process differs slightly based on your filter type. Let me guide you through the specific steps for each system to help you achieve the best results.

Backwashing a sand filter

A sand filter's backwash process reverses water flow through the sand bed using a multiport valve. Here's the step-by-step procedure:

1. Turn off the pool pump completely
2. Attach your backwash hose securely to the waste port
3. Rotate the multiport valve handle to "Backwash" position (ensure it locks in place)
4. Turn the pump back on and run for 2-3 minutes or until water in the sight glass runs clear
5. Turn off the pump again
6. Rotate the valve handle to "Rinse" position
7. Turn the pump on for 30-60 seconds to reset the sand
8. Turn off the pump
9. Return the valve to "Filter" position and restart your system

Backwashing a D.E. filter with a multiport valve

D.E. filters need extra steps because they use diatomaceous earth powder to filter water:

1. Shut off the pump at the breaker
2. Connect the backwash hose to the filter's waste port
3. Turn the multiport valve to "Backwash" position
4. Restart the pump and let it run for 2-3 minutes until water appears clear
5. Turn the pump off
6. Set the valve to "Rinse" position
7. Run the pump for 20-30 seconds to clean plumbing lines
8. Turn off the pump
9. Return the valve to "Filter" position
10. Add the appropriate amount of fresh D.E. powder through the skimmer

Backwashing a D.E. filter with a push-pull valve

Push-pull valves work differently than multiport systems:

1. Turn off the pool pump
2. Connect the backwash hose to the backwash port
3. Twist the valve handle and pull up to the backwash position
4. Turn the pump on and run for about 3 minutes
5. Once water runs clear, turn the pump off
6. Push the valve handle down to "Filter" position and twist to lock
7. Restart the pump and allow air to bleed from the system
8. Add fresh D.E. powder to recoat the filter grids

The backwashing process continues even after you reverse the water flow. Your filter needs several additional steps to function at its best and keep your pool water crystal clear.

Rinsing the filter properly

Set your filter to "Rinse" mode right after backwashing to stop leftover debris from entering your pool. Let the rinse cycle run for 15-30 seconds until the sight glass shows clear water. This significant step puts the filter media back in place for the best filtration. Your pool will get fine dust particles if you skip this step, which defeats the purpose of backwashing.

Refilling D.E. powder if needed

Diatomaceous earth filters need fresh D.E. powder to replace what was lost during backwashing:

1. Measure the right amount from your filter's manual (about 80% of the normal amount for post-backwash refills)
2. Put your filter in "Filter" mode
3. Mix the D.E. powder with water to make a thin, creamy solution while the pump runs
4. Pour this mixture slowly into the skimmer nearest to your pump
5. Let the pump run at least 30 minutes so the D.E. spreads evenly on the filter grids

You should wear a protective mask at the time you handle D.E. powder because it can harm you if inhaled[163].

Checking water level and chemical balance

Backwashing removes much of your pool's water, so check and adjust the water levels[183]. Test and balance your pool chemicals next since the water chemistry changes after backwashing. This step helps prevent algae growth and keeps your water clear.

Resetting the filter valve and pump

Turn off the pump completely before you restart your system. Move the multiport valve back to "Filter" position and check that it locks properly[183]. The new pressure reading on your gage becomes your baseline to know when to backwash next time. Remember that changing the valve position while the pump runs can damage internal parts and create pressure buildup.

Backwashing your pool is one of the most important maintenance tasks that keeps your water crystal clear and your filter working at its best. This piece covers everything you need to know - from what backwashing does to the right techniques for different types of filters. This simple process stops pressure from building up, helps your equipment last longer, and keeps your water chemistry balanced without much work.

Your pressure gage is the best way to know when to backwash - do it when readings go up 8-10 PSI from your normal level. On top of that, it helps to look out for signs like cloudy water or weak flow from return jets. The whole ordeal usually takes just 5-7 minutes but gives your filtration system huge benefits.

Sand filters need monthly backwashing, while DE filters need attention about six times a year. The steps after backwashing are just as crucial - you need to rinse really well, add DE powder when needed, and check your water's levels and chemistry.

Pool owners often skip proper backwashing techniques, but these simple steps make all the difference between constant maintenance headaches and easy swimming seasons. Making backwashing part of your regular pool care makes sense. Your filter works better, your chemicals are more effective, and you end up spending less time fixing problems and more time enjoying your well-kept pool.

Łaskawiec, Edyta. 2023. "Quality Assessment of Sludge from Filter Backwash Water in Swimming Pool Facilities" Sustainability 15, no. 3: 1811. https://doi.org/10.3390/su15031811 

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