Backwashing Your Pool Filters

It’s vital that, to get the most out of your swimming pool, you help keep the water as clean as possible. Your swimming pool filter and pump work tirelessly to help sweep any unnoticeable debris from out of the water, so you must help keep it running to its full potential.

Many things go into ensuring your filter system remains active while using your swimming pool. In a recent blog, we went into detail about how to prime your swimming pool pump. Here, we’re talking about another simple yet essential part of regular filtration maintenance.

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What is Backwashing for Swimming Pool Filters?


A backwash is just as the name suggests. Using the pump’s filtration system, backwashing reverses the flow of water through a pump, forcing any waste that has built up out of the pool through a waste valve.

Why is Backwashing Important for Swimming Pools?


To understand the importance of the backwashing treatment, you need to know how pumps work to keep your water clean.

Pumps create a consistent cycle, forcing the pool water through a system of filters before releasing it, newly cleaned, back into the pool. Most people know of the strainers, small buckets that can be found often around the side of swimming pools. These strainers collect the large debris that is being sent through the pump’s system.

However, what about the tiny grains of dirt that fall through the strainers? This is where the swimming pool filter comes into play. Often filled with sand or a similarly fine compound, the filter can collect the tiny pieces of debris while allowing the clean water to flow through and return to the pool.

Fine sand similar to that used in a swimming pool filter

Relieving the Pressure

The large strainers are often simple to clean by simply removing and emptying them while the pump is off. However, the pump is a bit more challenging. Over time, the swimming pool filter becomes clogged by all the dirt it has collected. This build-up increases the pressure of the water flowing through the pump.

As previously mentioned, backwashing reverses the flow of water through the pump. Through this process, dirt collected by the filter can be removed and released from the pool. For this reason, backwashing is a vital part of swimming pool maintenance.

When Should I Backwash My Swimming Pool?


The telltale sign for when a swimming pool urgently needs backwashing is when the pump’s pressure has risen due to the clog. As a general rule, if the pressure of your pump is eight-to-ten psi above its regular reading, you need to backwash the filter.

However, for the general health of your pool’s pump and filter system, backwashing should become part of your routine. During its season of operation, your swimming pool pump should be backwashed at least every week, and more frequently during heavy use.

Flowing swimming pool water

How to Backwash A Swimming Pool


Thankfully, the process for backwashing a swimming pool pump and filter is straightforward and takes just a few minutes. While there can be some differences between systems, many of them follow a similar procedure as outlined below.

Note that you’ll need a backwash hose for this process. Otherwise, the contents of the filter are released back into the pool.

1. Prepare the Pool

First things first, you need to turn your pump system off. For the longevity of your pump, it should always be turned off first when performing procedures such as this and priming.

Once the pump is off, turn the valve on the pump onto the backwash setting (the name may differ slightly). Some pump systems may have a waste valve – if so, open this and follow the instructions for your system, although they often run in a similar way to this.

Once the correct setting is in place, attach the hose to the backwash port.

A swimming pool with clear water

2. Backwashing Your Swimming Pool

Once everything is in place, turn on your swimming pool pump. When you turn it on, the backwashing should start to take place, and dirty water should begin leaving the hose.

Note here that it’s essential to consider how you dispose of this water, as it is chemically-treated. Ideally, use a drain to get rid of the water. Allow water to run through the hose for around 60 seconds, or until the water begins to run clear, then turn the pump off.

3. Rinsing Your Pump Filter

After the backwash, you should turn your pump valve to a setting commonly called rinse. What this does is return the pump to its regular route but keep it going through the backwash port. This process allows the pump and filter to collect and remove any debris that may be left in the system.

Turn on the pump again and allow this to run for around 15-20 seconds before turning the pump off again.

4. Returning to Normal Service

Once the rinse is completed, so is the backwash process. Remove the backwash hose, being mindful of any debris left inside, and reset the main valve to its standard filtration. Once this is complete, you can turn your pump on again as usual.

A swimming pool pump system with clear water

Common Swimming Pool Backwash Problems


As shown above, the process of backwashing for swimming pools is quite straightforward. However, it is possible that you may encounter problems during a backwash. Here are common issues and their relevant solutions.

Still Running Dirty Water After 60 Seconds

If you haven’t performed a backwash recently, there’s a chance that more debris has been collected in the filtration system than can be removed in the recommended one minute. In this case, it’s recommended that you still stop the backwash system. Follow the instructions above through the rinsing procedure, then repeat the backwash.

Continue the process of one-minute backwash and twenty-second rinse until water begins to flow clear. You can continue to backwash for over the recommended one minute, but that can cause problems with the pump’s water flow, which is explained in further detail below.

Still Excessive Pressure in Pump System

Similarly with the dirty water problem above. If you’ve performed the backwash but there’s still signs of higher pressure in your pump, it could be down to excess debris. If a backwash hasn’t been performed in a while, do the process again to see if that solves the pressure issue.

If the pressure in your swimming pool is still too high, then the most likely cause (assuming there was no problem during the pump’s installation) is the filter system. In some scenarios, it may need replacing, so get in contact with your supplier.

Pool Pump Lost its Flow After Backwash

As eluded to above, if you backwash your pool pump for too long, it runs the risk of introducing air into the system. Air pockets can cause pumps to lose the constant flow of water that they need to keep working. If this happens to your system after a backwash, you may need to prime your swimming pool pump. If the problem persists, then there may be a more significant problem, in which case you should get in contact with an expert supplier who can help solve your issue.

A woman with her feet in a clear swimming pool

We hope that this guide helps when it comes to keeping your swimming pool filters running smoothly during the season! If you think your system might need upgrading or replacing, feel free to get in contact with us for professional advice. We sell a range of swimming pool pump and filter sets and have helped pool owners across the UK get what they need for a happy, healthy swim!