Pool Filter Maintenance 101

By Geoffrey Sperring

May 25, 2025

Has your pool gone cloudy again? Your pool filter plays a key role in keeping the water crystal clear and is as important as keeping the pool chemistry right. A blocked or bad filter allows bacteria and algae to collect, resulting in green or cloudy pool water. This is why regular pool filter maintenance is essential.

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Pool Filter Maintenance: How Often Should I Clean My Pool Filter?

Knowing how often to maintain your pool filter system is crucial. Homeowners generally use one of two methods for deciding when to clean the filter.

Measuring the Back Pressure

The pool filter has a pressure gauge fitted to the multiport valve that measures the back pressure in the filter. If the pressure is too high, the filter needs cleaning. As a general guide, if the pressure is 8 psi above normal, it's time to clean the filter. Some gauges have markings that correspond to the normal working range and show when cleaning is needed.

Using a Pool Filter Cleaning Schedule

Some homeowners find it easier to complete pool filter maintenance on a schedule. The right timing depends on the type of filter, the size of the pool and how often it's used. Here are some guidelines:

Sand filter. Backwash the filter once a month. You may need to do it more frequently in the summer.
Cartridge filter. Remove and rinse the cartridge filter monthly.
Diatomaceous earth filter. Backwash a DE filter at least every 3 months and more often in the summer. You also need to top up the DE powder.

What Are the Signs of a Bad Pool Filter?

Pool filters are reliable, but eventually their performance may deteriorate. The filter medium may become clogged or damaged. Signs of a bad pool filter include:

Cloudy water. If the water stays cloudy after cleaning the filter, it’s a clue that the filter isn't catching dirt and algae properly.
Poor water circulation. The water flow doesn’t increase after cleaning and the pool cleaner is sluggish. Poor circulation is generally caused by a blocked filter, but it also may be a symptom of a worn-out pump.
High back pressure. If the pressure remains high after cleaning, the filter medium is likely clogged and needs replacement.
Low back pressure. A lower-than-usual pressure is a sign the filter medium is depleted or damaged, allowing too much water to flow through the filter. Similarly, it may show that the multiport valve is worn.
Frequent backwashing. The need to backwash often indicates the filter medium is blocked. This may be caused by debris such as a plastic bag or leaves or signal that the filter is irreversibly clogged.

What Is Backwashing?

Backwashing is an essential part of pool filter care. During backwashing, you reverse the flow of water through the medium to flush debris from the filter. Dirty water is dumped down a conveniently situated drain or onto the lawn.

How Do I Backwash My Pool Filter?

Here's how to clean a pool filter:

Set the multiport valve to backwash and then switch on the pump. The backwash position directs water in reserve through the filter.

Continue backwashing until the water coming out is clear.

Set the valve to rinse for a few minutes to flush larger particles. Don't use the waste position, as this bypasses the filter.

How Long Should a Pool Filter Last?

Pool filters last for around 5 years, provided you're diligent about maintenance. Depending on the type, you can extend pool filter life by changing the filter medium and performing regular servicing.

Sand Filters

It's recommended to do a pool filter sand change every 3–5 years. Remove the multiport valve. Cover or remove the lateral water distribution pipe inside the filter. Remove the old sand with a cup. Check for cracks and replace the seal between the valve and the filter housing. Clean the lateral and refill the filter halfway using special pool sand. Don't block the lateral pipe.

Cartridge Filters

These filters use a special cartridge. Open the filter by releasing the clamp and remove the old cartridge. Make certain the filter internals are sound and replace the cartridge with a new one.

DE Filters

Remove the valve and extract the grids that hold the diatomaceous earth. Clean them with a hose or using a diatomaceous cleaning solution. Check the tank for damage and reinstall the grids. Replace torn, damaged or blocked grids.

Add the required amount of diatomaceous earth through the leaf skimmer. Don't add too much or it may clog the filter. If this happens, backwash for a while.

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What Are the Different Types of Pool Filters and Their Pros and Cons?

The three main types of pool filters are:

Sand filters. According to HomeGuide, sand filters cost between $250 and $1,000 (CAD 349 and CAD 1,398) to install. They're reliable, robust and economical. On the other hand, the filtration isn't as good as they need frequent backwashing, and the sand must be replaced periodically.
Diatomaceous filters. A DE filter costs between $550 and $1,300 (CAD 769 and CAD 1,817) installed. The filtration quality is excellent, but you must top up the DE after each backwash and clean the filter grids yearly.
Cartridge filters. Cartridge filters cost between $250 and $1,200 (CAD 349 and CAD 1,678) installed. Pros include good filtration, simple cleaning and easy replacement. The main cons are the need to buy new cartridges every 3 years, and they're more susceptible to damage.

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