Pool Filter Not Circulating Water? (Possible Causes & Fixes)

Matthew Mountain
by Matthew Mountain

Swimming pools are beloved fixtures of modern homes, but they don’t run properly unless they have effective filtration systems. The average residential pool can circulate its entire volume of water every six hours, which means the average pool filter can turn over 36 gallons of water per minute.

With such a significant job to perform, it’s no surprise that pool filters don’t circulate water correctly all the time. If your pool’s filter is malfunctioning, here’s what might be affecting it.

Improper pool filter circulation can be caused by low water pressure, blocked lines, a dirty filter, filter neglect, and a variety of air-related issues. Most of these problems can be remedied by the pool owner, though the complex ones should be addressed by a licensed pool technician. Also, a pool owner may be legally obligated to fix their circulation issue.

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Purpose of Pool Filters

A swimming pool must have a filter, as it’s this device that collects debris, leaves, dead insects, and other particles that somehow end up in a swimming pool. Pool filters are so important that numerous places have laws that dictate how fast pool water can be circulated. A pool’s size and the amount of water it holds largely dictate how fast water can be circulated.

These laws are in place to ensure that pools are kept clean and safe at all times. Most pools have a drain or two at the bottom, and then there are skimmer drains on the sides. All these drains are there for the same reason—to catch debris that’s floating around the pool before it reaches the pump.

If debris is heavy, it usually sinks to the bottom of the pool where the drain catches it. Light debris, on the other hand, usually floats into the side drains. One can also use a strainer to remove any of the items that the drains don’t catch.

Kinds of Filters

Some filters contain fine sand particles, and these are employed to catch small debris. Other systems employ a diatomaceous earth filter, and this is made using a chemical powder called a diatom. There are also corrugated paper and polyester cloth filters, and these must be cleaned routinely. In fact, no matter what kind of system your pool employs, you should never forget about cleaning it.

Why Pools Fail to Circulate Water Sometimes

Every pool needs proper water circulation, as without this the pool water would harbor a variety of organisms. Circulation is also important in dispersing chemicals and disinfectants throughout the pool. Moreover, circulation ensures that pool water reaches the skimmer and pump, where bacteria and germs are properly removed.

These three reasons, along with a few others, underscore why pool water circulation is so important. A pool that isn’t able to circulate water could very well end up being a hazardous fixture.

The following sections will describe what causes a pool to not circulate water properly, and remedies to these problems will be suggested as well.

Low Water Level

Your pool’s water level will play a big role in determining how well your filter operates. That’s because a filter is designed to operate as a vacuum, sucking in as much water as it can take. Therefore when air enters the system, such can damage the motor, as the filter is only supposed to take in water.

If air is entering the system, this could be because the water levels are inadequate; particularly, they’re below the skimmer. If this happens, you should add water immediately, as without adequate water there won’t be any circulation.

To remedy this problem, first, turn off the filter pump. Next, raise the water so it’s at least halfway above the skimmer. Once the water is at an adequate level, the pump can be turned back on.

The Lines Are Blocked

Poor pool water circulation can also be caused by blocked lines. Lines are often blocked by debris, with leaves being the most common culprits. If you live somewhere where wind is as frequent as leaves falling from overhead trees, you should expect clogged lines to be somewhat of a frequent problem for your pool.

Of course, you can stay on top of leaf removal to better ensure you don’t have to deal with clogged lines, but even the most diligent person can fail to keep up with the rate at which leaves fall in some places sometimes.

You should at least clean out the basket daily. Remove everything inside and ensure there are no cracks or dents before reinserting. If you don’t do this, it’s likely you’ll be dealing with a poor water circulation problem sooner rather than later.

Filter Neglect

When a pool filter is neglected and not maintained properly, water circulation problems are bound to arise. If you notice that the filter’s pressure has risen significantly, this may be because the filter has been operating too long without proper maintenance.

To know what the filter’s pressure level is, look at the gauge at the top of the system. This is a common arrangement for pool filters. The manufacturer of your filter most likely outlined what the normal pressure range is for your filter, so you should consult your system’s manual to see what this range is. If you don’t have this with you, surely you can find one online.

When pressure is high, you should backwash the system, as this is what’s recommended by most manufacturers. Sometimes, however, backwashing isn’t enough, and in this instance, it’s best to take out the sand or diatomaceous earth filter media. After you replace whatever you removed, reinsert the filter to see if the water circulation returns to normal.

Dirty Filter

A dirty filter can also lead to pool water circulation problems, and most filters get dirty and clogged if they aren’t taken care of properly for a while. Even under the best circumstances, a filter can get dirty because particles and small debris collect inside.

When you suspect your filter is too dirty, you should try backwashing the system. You’ll know your system is dirty when the pressure gauge is between eight and 10 pounds per square inch past the normal operating pressure for your system.

Pump Is Unable to Prime

As was mentioned earlier, air is not supposed to get inside a pool pump. A more significant air-related problem than the one discussed earlier is when air is coming into the system from a variety of spots. When this happens, air accumulates in the pump chamber, creating an airlock that prevents the proper amount of water from priming the pump.

In this instance, a system won’t have the suction power to pull water through the lines, so air won’t be expelled. One will have to manually remedy this situation. To address this problem, one must first uncover where all these air leaks are, as remedying these must come before addressing the pump suction system.

You probably won’t be able to uncover where the air leaks are coming from—especially if they’re very small—and this is why you should get a professional’s help. Specifically, someone who has the know-how and technology necessary to address this problem.

Another common air-related circulation problem is when the O-ring is leaking. This ring is found on the removable pump chamber’s cover. Simple replacement of this ring will fix this problem in most instances.

Related Questions

Since there are a lot of pool owners out there, it should be no surprise that many individuals have questions about pool filters and circulation problems. The common questions are answered below.

How often should a filter be cleared?

Pool filters need to be cleaned routinely, as doing so will prevent issues from happening often. You should clean your filter at least once a day, especially if you use the pool often. If your pool is under heavy tree cover, this may necessitate cleaning it more, as it’s likely debris and leaves will fall off and find their way into your pool.

Is filter replacement often necessary?

Filter replacements are not often necessary, but a replacement will be in your future if you refuse to take care of your system routinely. Most filter-related problems can be fixed by replacing components, but some issues will necessitate replacing an entire filter system.

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Final Note

In the end, if you notice that your pool is no longer properly circulating water, a variety of things could be causing this problem. Above, we talked about the importance of water pressure, lines, pumps, and filters, and if anything goes wrong with any of these facets, it’s likely a circulation problem will be the result.

The most obvious of the circulation problems is when air enters the system. This will be obvious to detect and easy to remedy as well. Blocked lines are another simple fix, and so is a dirty filter. When issues are more complex, it’s best to get in touch with a licensed pool technician, as these professionals handle pool water circulation problems for a living.

Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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