Cartridge v Sand Pool Filters - Which Is Best?
All pools need filters, including DIY swimming pools. Pool filters remove the microscopic particles in your water. Getting the right filter will mean the difference between safe, sparkling clear water all year round and unsafe cloudy water.
Ok, so the basics first. Your pool pump draws water from your swimming pool through the skimmer box and into your pool filter under pressure. The water is forced through either sand, glass or a mesh cartridge which traps the unwanted particles. Clean water is pumped back into your swimming pool through the return jets (sometimes called “eyeballs”). It is very important that you match your filter flow rate to the pump flow rate otherwise filtering efficiency will be seriously impacted.
Media Pool Filter – Sand
Unfortunately, we are not referring to a new app that filters out unwanted media ads on your smart phone. Media refers to what you choose to fill your filter with – either sand or glass. As you can see from the media filter image, the filter bowl holds a fair amount of media.
20 grade silica sand has been used for decades, hence the older term “sand filters”. Under a microscope, each particle of sand has jagged edges. It is these edges that capture the tiny particles in your water. Over about 5 years these edges are worn smooth, losing their filtering ability, and need to be replaced. A mid-sized sand filter will hold around 100kg of sand which costs $150 to replace. At an average of $30 per year, it is very cost effective.
Media Pool Filter – Glass
You can also use crushed glass (glass media) rather than sand. Why? The glass particles are smaller and harder than sand so they capture smaller particles from your water. It takes around 7 years for glass to be worn smooth and needing to be replaced. 100kg of glass media will cost around $300. At an average of $42 per year, it will not break the bank however it is more expensive than sand. If you are expecting your pool to be continually full of kids (called high bather load), glass will do a better job of keeping your water crystal clear compared to sand.
Don’t media pool filters waste a lot of water? To maintain a media filter, the media needs to be cleaned every month (or when the pressure gauge needle on your filter is pointing to red) by backwashing. Backwashing reverses the water flow direction through your filter which stirs up the media (it is like fluffing a pillow) releasing the contaminants. The dirty water is discharged into your sewer line or soak wells. A backwash is simple to do, takes a couple of minutes and discharges around 400 litres of water.
Media pool filters generally cost between $700 and $1,600 with top end models up to $2,100. It is important to check what the outer shell is made from. If your pool filter will be exposed to the sun, lean towards a fibreglass shell over injection mould plastic. Fibreglass is much more durable in the elements and will last a lot longer than plastic under the harsh Australian sun.
Cartridge Pool Filters
If space for your pump, filter and chlorinator is tight, a cartridge filter has a much smaller footprint than a media filter. Inside is a cartridge pool filter is an element that is usually several layers of fine mesh (like flyscreens however with much smaller holes). This mesh can filter smaller particles than a media filter and works much the same. Water is pushed under pressure through the mesh which traps the particles.
The cartridge can be easily removed and needs to be cleaned once per month initially. If you notice the cartridge is really dirty, you will need to clean it fortnightly. Or, every two months if it’s not that dirty after a month. High bather loads and pools with trees close by normally need more frequent cleaning. Cleaning is a bit more messy than media filters however still easy enough. Give them an overnight soak in a cleaning solution and a good wash out and you are done. We recommend having two cartridges so your pump and filter can still run while one cartridge is being cleaned.
Cartridge filters cost between $700 and $1,300 on average, with top end models up to $2,200. Replacement filters cost between $100 and $300. If regularly cleaned, they need to be replaced every 3 to 4 years. Without regular cleaning, you might replace them annually.
Key Takeaway – Cartridge filters have been popular over the last 10 years. However, there is a consistent trend of pool owners replacing them with media filters after a year or two. Why? Time and cost. Cartridge filters on medium and large size pools, or high bather load pools require a lot of cleaning. Owners want time in the pool, not working on it.
About The Author
My wife and I grew up playing in swimming pools. Our daughters learnt to swim in our backyard fibreglass swimming pool. There is nothing quite like hearing kids splashing about and giggling. As pools do, our pool became a social magnet for friends, family and neighbours which we loved. Helping customers to have their own pool and saving customers thousands on their pool and equipment is the best job in the world.
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