Welcome to our guide to media filters!
Whether you’re already a pool owner, or about to become one, it’s important to know about different types of filtration systems.
Today we’ll talk you through a common one: media filters.
Called “sand filters” in the past, because of the use of sand as the filtration medium, we now call them “media filters”, because consumers have a choice of new and different filter media.
If you’re wondering how to run your above-ground or in-ground pool with the best media filter, as well as what type of media to use, stay right here.
We’ll also cover cleaning and backwashing your media filter because maintenance is key to a sparkling pool experience!
In this guide to media filters, you’ll find:
- What media filters are
- How media filters work
- The kinds of filtration media
- Backwashing a media filter
- How long media filters last
- Finding the most suitable media filter for your needs
- How to change the media
- Alternatives to media filters
Let’s get filtering.
What Are Media Filters?
Media filters are one of three types of filter that you can have for your pool (the others are cartridge filters and DE filters).
Media filters are famously efficient, low-maintenance and inexpensive, making them a popular choice for Kiwis all around New Zealand.
They don’t need regular cleaning. Just change the media every five to ten years (depending on the media in the filter) and this miniature indoor beach will keep your swimming pool waves clean.
Swimming pool media filters are used for the same purpose as other swimming pool filters: they are powered by the pool pump and tasked with cleaning your pool by filtering out very small pieces of debris.
Great water circulation plays a key role in achieving this.
How Do They Work?
In a nutshell, the debris in your pool is caught in the filter, trapped on the surface of the media.The way the media traps the dirt depends on the type of media that is in your filter – some media rely more on attracting the dirt from the water and some rely more on trapping the dirt.
Research into filters about 20 years ago found that as the water travels through the filter, it’s cleaned by a combination of two methods – mechanical entrapment and electrostatic attraction.
- Mechanical entrapment is when the media captures the dirt in pits and hollows on the surface of the media. This is how it was believed sand filters worked. But research showed that this was not the only process at work.
- Electrostatic attraction is when dirt is attracted to the surface of the media by an electrostatic charge created as the water passes over the media surface. This is a bit like the charge you get when you walk on a carpet while wearing socks.
The harder the media is, the more of the electrostatic charge is created by the water passing over the media. This charge is a very effective way of trapping the dirt from the pool water.
Regardless of your media type, the more water that passes through the media filter, the dirtier the media gets.
In the beginning, this actually helps the filtration process as the sticky dirt acts as another filter layer.
After a while though, dirt builds up in the filter and it isn’t all removed by backwashing. This makes the media less efficient, and you may need to replace it. We recommend that you replace sand and zeolite about every five years, and glass every ten years.
Using the multiport valve (MPV)
The part of the media filter that you will use the most is the multiport valve – or MPV.
The MPV is usually mounted on the top of the filter tank, but it can be mounted on the side as well. This is what directs the water through the filter. It has six positions.
The positions and their functions are:
- Filter: This directs the water down through the media and then back to the pool.
- Recirculate: This directs the water straight back to the pool, missing the media.
- Waste: This directs the water straight down the backwash line to the drain, missing the media.
- Backwash: This directs the water up through the media and flushes the dirt down the backwash line.
- Rinse: Use this after backwashing to flush any debris out before going back to Filtre.
- Closed: This closes the valve and stops the water flow.
Whenever you need to change the setting of the MPV, you must turn the pump off first. This will help to prevent damage to the valve.
And that’s it, simple!
What Kinds Of Media Can I Use?
Media filters need specific types of media, so make sure you get the right kind.
You have a few options to choose from:
With a low environmental impact, glass is a great choice. Like the name suggests, it’s made from glass, but is still pretty smooth to the touch. It’s made from recycled glass, which reduces landfill waste.
The glass particles are all slightly different sizes, which makes it very effective at capturing the tiny bits of debris that make it into your filter. This is a great benefit.
Glass is harder than sand, so it creates more charge and attracts more dirt from the water, while capturing less of the dirt through mechanical entrapment. Over the life of the filter, glass will give you the best water quality.
Silica sand is mined, not manufactured – it’s normally graded river sand that’s been dredged up.
It used to be a popular choice for pool filter sand because its rough surface makes a great net for catching debris from the water.
Sand uses a mixture of both cleaning methods (electrostatic charge and mechanical entrapment). But overall, it doesn’t filter as well as glass does, because it doesn’t produce as much of an electrostatic charge.
Zeolite is a bit different to other types of filter media. This one is mined from volcanic rock minerals.
Zeolites are relatively soft and rely mostly on trapping the dirt by mechanical entrapment in a sponge-like structure. When Zeolite is first used in a filter, the water quality is amazing.
However, once the centre of the sponge-like structure of the Zeolite is filled up, the amount of dirt trapped becomes pretty much the same as sand.
It’s like your kitchen sponge: no matter how much you clean it, you can’t get all the dirt out of the centre of the sponge and it eventually needs to be replaced with a nice new sponge.
Choosing between the types of media
If you’re not sure which one you’d like to go for, get in touch with us and we’ll happily talk more about it with you and find the best one for your pool.
After you’ve installed this new toy, just like everything, it’s going to need cleaning sooner or later.
So, let’s look at that next.
Backwashing Your Media Filter
There are three occasions when you’ll need to pay attention to your media filter:
- When you backwash your pool to clean it.
- When you change the media in your media filter (after five to ten years).
- When you need to completely replace your media filter.
In some situations, the media in your filter may last forever. But in New Zealand, it is recommended that you do replace it from time to time.
If it starts to sound different, act differently, and operate at a different pressure range than before, these are key indicators that it’s probably time to look at replacing your media.
Also check that your pool pump is still working as well as it should be.
What is backwashing?
Backwashing is the process by which you reverse the flow of water to pick up all the dirt in the pump, and let it drain out of the waste pipe. This should clean your filtration system.
You should, ideally, do this twice a month, or as required. This is what your pressure gauge tells you so make sure it’s working!
You can read a bit more about the backwashing process in our Ultimate Guide to Pool Cleaning.
How Long Does The Media Last?
Usually five to ten years.
Fresh sand for sand filters has rough edges and, as we know, this efficiently captures and holds back micro debris passing through the sand.
However, over time the rough areas smooth out. This is because when you backwash the filter you don’t get rid of 100% of the debris that’s been captured. The small percentage that’s left builds up over time, rounding out the surface of the media.
The smoother the sand, the less effective the filtration.
You might start to notice the difference in your pool:
- Have you been using more shock than usual?
- Does the water seem cloudier more often?
- Does the pressure on the pressure gauge not drop after backwashing like it has before?
If this is the case, it has likely become more difficult for water to pass through the media.
Alternatively, the water is instead cutting straight through a weathered hole. This means that your filtration has dropped to nil because the water is taking the path of least resistance through the filter.
When this point is reached, it’s a good time to change the media in your filter and start again with those rough and ready edges!
Don’t forget, you can chemically clean your media once a year, which will give you a much longer life, using Focus Filter Degreaser & Cleaner.
Finding The Most Suitable Media Filter For Your Needs
There are many types of media filters for swimming pools, so we’ve narrowed our recommendations down to our favourites.
It’s important to consider what size filter you need for your pool, taking into account whether it’s an above-ground pool or an in-ground pool and the size of your pool pump.
Both of them are:
- Suitable for above ground and in ground pools of all sizes, spa pools and water features.
- Great for sparkling, crystal clear water using the latest technology.
There’s also the EcoClear Glass Pool Filter Media which takes it one step further.
Whichever media you choose, you’ll need to know how to change it.
Let’s find out how.
Changing The Sand In Your Filter
If you’re finding that your sand does need to be changed, then roll up your sleeves and follow these steps – or contact your local pool shop.
What you’ll need
Some of these things you might have at home, and others you may need to purchase for your pool.
Note: No special sand filter cleaning chemicals are required at this stage.
- Turn the filter and pump off. including any timer set for them to come on again.
- Drain your filter tank. Beware this may take a while (you can do the first two steps first and come back later to complete this list!). Your filter tank may not have a drain fitted.
- Remove the multiport valve (by unscrewing if possible, by cutting the pipe if necessary).
- Cover the standpipe with duct tape. This prevents sand getting in and being flushed back into your pool when you turn the pump on again.
- Vacuum the sand out of your sand filter with your wet-vac. If you don’t have a wet-vac you can scoop it out with a cup, but this will take all weekend and you’ll likely end up buying a wet-vac in the end anyway!
- Rinse out the tank with your garden hose.
- Check the tank, standpipe, and laterals for cracks with your flashlight to make sure there’s no damage.
- Fill the tank halfway with water. This protects the laterals from the full weight of the media when you pour it in.
- Add the new media. Wear your mask to do this, as pouring media kicks up a lot of dust. Seeing as media comes in 20kg plastic bags or so, this is where your knife comes in handy (to cut the bag open).
- Fill the tank and reconnect everything.
- Backwash the filter until the sight glass is clear.
- Rinse the filter by first shutting the pump off, turning the setting to rinse, and turning the pump back on again. Rinse for up to one minute.
- Run the filter by first shutting the pump off again, turning the setting to filter, and turning the pump back on again. Leave it on for a while.
- Read the pressure gauge: this is now your filter’s ‘normal’ pressure. Make a note of it! You’ll need to know this figure so that you’ll know when to backwash. You should backwash when the pressure is showing 30-40 kPa above the normal pressure level.
The Alternatives to Media Filters
Here in New Zealand, one of the most common alternatives to a sand filter is a cartridge filter.
Both types have their benefits, so let’s explore them.
Media filters should last longer, if you take care of them properly.