How To Backwash Your Pool Filter (in 6 Easy Steps)

Backwashing is an irreplaceable and unavoidable part of owning a DE or sand filter.

This process removes the debris and other contaminants from the filter without requiring a full cleaning session. Backwashing also lowers the filter’s pressure gauge, preventing cavitation and overheating.

To backwash your pool filter, follow this method:

1. Turn the filter valve to backwash
2. Attach a backwash hose
3. Turn on the pool pump
4. Rinse the filter after backwashing
5. Turn the valve to circulate
6. Add DE or sand if needed

In this article, I’ll show you the step-by-step instructions for backwashing and rinsing your swimming pool filter.

I’ll also answer the most common questions and backwashing, including how long and how often it should be done. Let’s get started!

1. Turn the Multiport Valve to Backwash

Your sand or DE filter has a multiport valve, mounted valve, or multi-directional valve. This valve lets you rinse, backwash, and circulate the pool.

Some of them also allow you to drain the pool, but it’s typically only found on high-end multiport valves. Your sand filter works by compressing the sand and filling it with debris that needs to be removed through backwashing.

Keep these tips in mind when turning the multiport valve:

• Turn off the pump before moving the valve. The pump will immediately send the water through the valve, causing the water to shoot out of the backwash port without a hose. Not only does this dirty water cause issues, but the instant pressure change can damage the multiport valve and require repairs.
• If sand or debris comes out of the backwash port without the pump running, there might be a broken part. A cracked manifold, broken gasket, or damaged multiport will leak sand into the swimming pool and out of the backwash port. Open the pool filter and replace any broken parts if necessary.
• You might have to tilt the valve’s handle backward. Some multiport valves have child locks that have to be tilted to rotate. This setting prevents children and pets from bumping the valve and changing the water flow’s direction. Gently rotate the valve to ensure you don’t break the handle.

2. Attach a Backwash Hose to the Filter

Backwash hoses serve two purposes:

1. They help you direct the water flow. Your valve turns the water to the backwash setting, so you need a hose to choose where the dirty water goes. I recommend contacting your city to find out where you can flush the water. Some places have laws against draining pool water into the gutter.
2. Backwash hoses are thick enough to handle the debris but flexible enough to move wherever you need them to. They’re built differently than traditional hoses. You can’t substitute a backwash hose with any other hose. You could risk damaging the filter by sending some of the debris back into the tank.

The Gorilla Swimming Pool Backwash Hose is a 50-foot hose with a thickness that’s several times larger than most of the competition. Not only does it prevent holes and tears, but this hose also has an excellent grip. You don’t have to worry about the chlorine and other chemicals destroying the inner lining, either.

Make sure you use a backwash hose clip to secure the hose; Otherwise, it’ll launch off the valve the second you turn on the pump.

Luckily, the aforementioned Gorilla Backwash Hose comes with the clips you need. You can also find the clips at swimming pool stores and automotive stores since they use the same clips for many car hoses.

3. Turn on the Pool Pump

Turning on the pool pump will push the water into the filter and through the multiport valve. The water goes in whichever direction the valve points.

If it’s set to the BACKWASH direction, the water will flow through the backwash hose. You can’t backwash a pool filter without turning on the pump.

While you could wait until the pool timer turns on the pump, it’s best to do it manually. Switch on the pump at this point in the process to backwash the filter.

You shouldn’t let the timer turn on because it won’t turn off when you’re done backwashing the filter in a couple of minutes. You’ll end up draining the pool.

4. Rinse the Filter

Rinsing the filter removes the excess debris from backwashing the plumbing.

There’s a lot of sand, contaminants, and grime in the filter that needs to be rinsed; otherwise, all of the debris will go back into the filter. You’ll have wasted your time, not to mention that the debris can clog the filter again.

If you don’t rinse the filter after backwashing it, some of the debris can go into the pump. Your pump will make a grinding noise from the sand and other particles cycling through the impeller.

This issue can overheat the motor, forcing you to replace it. It’s well worth the time and effort to rinse a pool filter!

5. Turn the Valve to Circulate

Once you’re done backwashing and rinsing the filter, turn off the pump and push the valve back to the CIRCULATE or FLOW setting. This setting lets you filter the water as you normally would.

It’s important to remember to turn the valve after backwashing, or all of the water will drain out of the swimming pool. This costly mistake can force thousands of gallons out of the pool.

If your pump doesn’t circulate after backwashing, check the water level. The water should be above the skimmer basket (or whichever inlet is the highest).

Backwashing drains a little bit of water out of the pool, especially if you backwash the pool for too long. You only need to backwash the filter for a few minutes.

6. Decide if You Need to Change the Sand or DE

Backwashing your pool filter is a great way to reduce the PSI and clean the sand or DE, but eventually, you’ll have to replace the filter media.

DE filters are about twice as good as most sand filters, so it needs to be replaced more often. There’s a lot more debris and oil in a DE filter.

Here’s how you know if you need to change the filter media:

• Check the DE levels and add however much DE is missing every three months.
• Replace all of the sand in your sand filter every three to five years or once per year with an Intex or Bestway filter (make sure you know how much sand you need for your Intex filter).
• It’s time to replace the filter media if the PSI doesn’t drop more than 5 to 10 PSI after backwashing it since the media is saturated.

How Often Should You Backwash A Pool Filter?

You should backwash a pool filter once per month. Set a routine schedule to backwash the filter on the same day each month or whenever the filter’s PSI exceeds 25.

The pressure gauge on top of your filter is a clear indication of when it’s time to backwash the filter. You should backwash the filter until the PSI drops to 10 to 15 on the gauge.

I suggest backwashing your filter every 4 to 6 weeks, based on the manufacturer’s recommendations, PSI, and the pump’s performance.

Your pool pump will be much slower and less effective when the PSI is too high. Backwashing your filter regularly will prevent algae blooms and chemical stains.

Failure to backwash your filter often enough will also cause these issues:

• The high filter pressure can crack the manifold, warp the O-rings, and damage the filter tank.
• Leftover debris will eventually pour into the plumbing and back into the pool.
• The pump will overheat from working too hard while trying to push the water through the clogged filter.
• Most of the O-rings, gaskets, and seals on your equipment pad will warp or become misaligned.

Pro-tip: Broken pressure gauges don’t read the correct PSI. The easiest way to know if your filter’s pressure gauge is broken is to check if it moves when the pump is off or after backwashing the filter. The PSI should drop to 0 when the pump is off, then raise when the pump turns on. If it doesn’t move, it’s time to contact the manufacturer for a like-for-like part number.

Do You Turn On Filter To Backwash?

You turn on the filter to backwash by turning on the pump. Pool filters don’t have motors, so you need to activate the pump to move the water through the backwash hose. It’s also important to keep the pump off until the multiport valve is on the backwash setting.

Failure to turn on the pump while backwashing your filter will prevent the water from moving. The water won’t move, so the backwashing process won’t do anything. Furthermore, your pump will shoot dirty water through the backwash valve when the timer turns on.

I suggest turning on the pump manually to backwash the filter rather than waiting for the timer to kick in.

However, you don’t need to turn on your heater, salt system, booster pump, or vacuum when backwashing a pool filter. In fact, it’s best to leave these pieces of equipment off while backwashing because it prevents them from getting air bubbles into the system.

There’s no way to avoid backwashing a DE or sand filter. However, it’s important that you don’t backwash or rinse it for too long. Either of these processes can drain the pool too low, damage the equipment, and more. If you need to know how long to backwash or rinse your pool’s filter, read on.

How Long Do You Rinse After Backwashing A Pool?

You should rinse for up to 30 seconds after backwashing a pool. The rinsing process removes excess debris from the sand or DE, preventing it from getting into the plumbing.

This often-overlooked step is crucial to protect your filter from wear and tear while lowering the PSI and reducing the chances of an algae bloom.

Rinsing your pool filter between 15 to 30 seconds is an effective method because it doesn’t require too much water.

You don’t need to rinse the pool filter nearly as long as you backwash it because you’re simply removing the leftovers. Too much rinsing is unnecessary and can drain your pool too much.

I also encourage you to rinse the filter after backwashing because it cleans the backwash hose. These hoses are often neglected, leading to tears and corrosion.

With a proper maintenance routine, you can get several years out of a backwash hose. Rinsing the hose is an excellent way to preserve it. You could also use a garden hose for trapped debris.

How Long Should You Backwash A Pool?

You should backwash a pool for two to three minutes at a time. Backwashing it too much will lower the pool water below the highest inlet, letting air bubbles into the plumbing.

These bubbles can damage the pump’s motor and impeller. However, not enough backwashing will prevent the debris from getting through the hose.

The best way to know if you’ve backwashed the pool enough is to look for these two signs:

1. The pool’s PSI should drop to about 10 to 15 on the filter’s pressure gauge. Many experts recommend backwashing your swimming pool when the PSI gets over 20 to 25. You don’t want the pressure to get too high, or it will limit the pump’s functionality and cause plumbing cracks and leaks.
2. There should be clear water flowing from the backwash hose. This is a common sign that your sand or DE has been thoroughly cleaned. You might notice brown or gross-looking water at first, but it’ll go away after a couple of minutes. If the backwashed water has sand in it, there’s likely a crack in the center pipe or manifold.

Some manufacturers recommend backwashing for up to five minutes. I suggest always contacting the brand or looking through the user’s manual to know how long you should backwash your pool filter.

There are many different filter variants, such as Zeolite sand and quad-DE filters. These unique styles require special backwashing routines.

Jonah Ryan

Jonah has worked for several years in the swimming pool industry installing and repairing equipment, treating pools with chemicals, and fixing damaged liners. He also has plumbing and electrical experience with air conditioning, ceiling fans, boilers, and more. When he’s not writing for Temperature Master, he’s usually writing for his own websites, LawnCareLessons.com and DIYByHand.com.