Cartridge Filters vs Sand Filters: Your Unfiltered Guide to Pool Filters

Grinding, whirring filters that have you leaving your swim day with a headache, murky spots on your pool surface, algal blooms blossoming all over what USED to be clear waters, a suspicious stench by your swimming pool — these are all signs that your pool filter needs an upgrade, or a replacement, or some serious maintenance, ASAP! 

Read on to find out all the finer details of filtration, to uncover the UNFILTERED guide (pun very much intended!) on which filter to buy based on YOUR pool’s unique needs! 

Do I really need a pool filter?

No one wants to be swimming in murky, algae-infested, potentially pathogenic waters— that’s why pool filters are an absolute must-have for your pool.

Think of pool filters as your kidneys. Your chemical chlorinators do all the CHEMICAL sanitisation — pH balance, etc.—, but your pool filters are what do the PHYSICAL heavy lifting. 

All that gunk and debris that would otherwise be floating around in your pool after a big swim day, are trapped by your pool filters working in conjunction with your pool pump. The pump-filter combo also work to circulate water through the pool, thereby preventing algal and bacterial growth, while also helping distribute chemicals evenly throughout the pool.

How does a Pool Filter Work?

Let’s get technical! 

The physics behind a pool filter+ pool pump combo is pretty basic:

The pump sucks in water from the skimmer (at the surface of the pool) and the main drains (at the bottom of the pool).

Large debris like big leaves are caught in the skimmer basket and the pump strainer basket before reaching the filters.

The water is then discharged into the filters where further magic happens! The finer debris in the discharged water is trapped by the filter medium (sand or cartridge, depending on which type of filter you’re using— we’ll get to that soon!), which then lets clean water through into the pool, or the chlorinator if you’re using one (we recommend that you do!). 

The chlorinator does the chemical heavy lifting and sanitisation, and finally, you’ve got crystal clear pool water coming back into your pool — all sanitised and ready for you to take a dip in!

What’s the difference between a sand filter and a cartridge filter?

That’s a great question! The technical process of both filters is basically the same. The biggest difference — and it DOES make a world of difference— is in the filter MEDIUM: this is the component of the filter that traps the debris, the component that does the actual filtration bit.

Sand filters have a specially graded silica sand as their filter medium. Slotted lateral pipes at the bottom of the sand filter pass the water evenly up through the graded sand, which traps the debris.

Cartridge filters, on the other hand, have a cartridge of pleated fabric (usually of polyester material), to trap the debris within it. 

So… Sand Filters vs Cartridge Filters: Which One is Superior?

Now that we’ve got the preliminary questions out of the way, we are finally going to be answering the big question! 

WHICH pool filter is superior?

Well, it depends. There’s no right answer to this, because it’s something that needs to be decided solely based on your pool’s needs! But we can give you all the pointers you need, in order to make that final decision for your pool.

Here are a few things you need to take into consideration, when deciding which pool filter to buy:

1. Efficiency

The efficiency of a pool filter is calculated on the basis of its micron level— that is, the measure of the size of particles or debris it can filter.

The smaller the micron level, the more efficient your pool filter is at catching the smallest particles and making sure not even the finest debris gets through to your pool! 

Sand filters can filter in the range of 20-40 microns, while a Cartridge filter has a filtration range of 10-15 microns.

Based on this measure, cartridge filters ARE more efficient at trapping smaller debris— but that alone cannot be the deciding factor for your choice of pool filter. Which brings us to the next factor you’ll need to consider: 

2. Filtration needs and Pool Size

What are YOUR pool’s filtration needs? 

Do you live in an area that’s bombarded with heavy debris on the regular? Maybe you’ve got factories or farms or pollen dust in the vicinity. Maybe you’ve got frequent swimming going on at your pool, and/or maybe it’s a residential inground pool. If so, a sand filter is your best bet, because they are built for reliability with heavy debris or frequent swimming. They also work best with larger pools, because they handle higher water volumes well. And you don’t have to necessarily compromise on clearer waters either— sand filters like the Zodiac Titan ZT800 32" Fibreglass Sand Filter can filter down to 3 microns because it uses Diamond Brite as an alternative filter media to sand!

Generally, however, cartridge filters are the superior option if your priority lies in sharper water clarity. They work best for smaller, or average-sized pools, unless you’re choosing to invest in the AstralPool Viron QL 420 Cartridge Filter which is also suitable for residential or commercial pools or spas — that gives you the best of both worlds: large pool AND crystal-clear waters! 

3. Cost-Effectiveness 

Sand pool filters are generally considered the least expensive option, but that doesn’t mean you should be discounting cartridge filters right away on the basis of price.

While sand filters have a lower initial cost, cartridge filters don’t require any backwashing which means you get to make big savings on water and chemicals over time! The AstralPool Pool and Spa Cartridge Filter XC 250, for instance, takes just 100 litres of water to clean the elements instead of backwashing thousands of litres to clean a sand filter!

4. Maintenance

Sand filters offer low-maintenance as one of its biggest upsides: all you need to do in terms of maintenance is backwash the filter. The sand will need to be replaced only every 5-7 years!

Cartridge filters, meanwhile, do carry relatively higher maintenance costs, with deep-cleaning required every 1-2 years, and the cartridge needing to be replaced every 2-3 years.

5. Environmental-Friendliness

If you’re trying to go green— cartridge filters are probably your best bet because they save big on water and chemicals (see above!). While sand filters can waste up to thousands of liters in backwashing, cartridge filters like the Zodiac ZXC250 Cartridge Filter only take up a 100 liters to clean its elements! It must be noted, however, that cartridge filters in general can create waste through disposable cartridges.

Sand filters use up a LOT of water in backwashing, but the sand itself needs to be replaced less often. 

In conclusion…

Which pool filter is superior? Cartridge filters, or sand filters? Each pool filter comes with its own set of pros and cons that you can consider before making your purchase. And if you’d like some customised advice, we at City2Bay Pool solutions are always happy to help!