Noticing algae or mould in your water filter? You’re not alone. Sometimes we will have a customer call to say they have algae growing inside their benchtop gravity water filter, either at the bottom of the tank, on the mineral pad or on the filter cartridge.
While this is a rare occurrence, algae can grow in water filters under specific environmental conditions. Understanding where the algae is coming from and how to prevent and treat it is key to ensuring the quality and safety of your drinking water.
In this guide, we take a closer look at why algae grows inside water filters, what to do when it does and how to prevent it from recurring. We’ll also explore when it might be time to upgrade your water filtration system.
In this video, learn what to do if you notice algae or mould growing inside your water filter. While rare, this issue can occur in systems where water is sitting too long in the tank, especially if exposed to sunlight and warmth. Discover how to properly clean your filter components, such as the cartridge and mineral pad, without using harsh chemicals.
If algae continues to grow, it could be a sign your water filter isn't fully equipped to handle your water's contamination. In such cases, upgrading your system may be the best solution for safe and clean drinking water.
Where Does the Algae Come From?
If you’re dealing with algae in your water filter, there are typically two possible sources: your water supply or your surrounding environment.
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Water Source
If you’re using rainwater, as opposed to city water, it’s entirely possible that algae or other microorganisms are already present in the water. Rainwater tanks, especially, can be susceptible to organic contamination if they’re not well-maintained. Leaves, debris, bird droppings and sunlight exposure can introduce nutrients and spores into the system. In such cases, your current water filter might not be powerful enough to handle the biological load. You may need to consider upgrading to a more comprehensive filtration system such as a benchtop or under sink water filter for additional pre-filtration and UV disinfection capabilities. -
Environment
If you’re on city water, which is typically disinfected with chlorine or chloramine, then the likelihood of algae entering your system through the water itself is very low. However, if you're still seeing algae in your water filter while using city water, it’s likely that spores from the environment are finding their way into your unit. This could be due to an open lid, inadequate sealing or exposure to external sources like dust, air or splashes from nearby sinks.
Why Does Algae Grow in Water Filters?
Even if your filter system starts out clean, several environmental factors can encourage algae to grow inside your water filter over time.
Sunlight: Algae are photosynthetic organisms. Exposure to direct or even indirect sunlight can promote growth.
Warmth: Warm environments, especially in summer, create ideal conditions for algae to thrive.
Lack of Disinfectants: After filtration, the water in the bottom tank is usually free of chlorine or other chemical disinfectants. While this is desirable for drinking, it also means there's nothing in the water to prevent biological growth once it has passed through the filter.
How to Clean a Water Filter That Has Algae Growing in It
Disassemble the Unit
Separate all components of the water filter — the top tank, bottom tank, filter cartridges, mineral pad, spout and lid.Clean the Housing
Use a mild dishwashing detergent and a non-abrasive sponge or cloth to thoroughly clean the inside of the upper and lower tanks. Make sure to rinse well to ensure no soap residue remains.-
Do Not Use Detergents on Cartridges
Filter cartridges, especially ceramic types, should not be cleaned with soap or detergents. Instead, scrub the ceramic cartridge gently under cool, flowing tap water with a scouring pad until the outer surface is clean. Dry Completely
Before reassembling, allow all parts — especially the filter cartridge and tanks — to dry completely. This helps prevent future microbial growth.Reassemble and Refill
Once everything is dry, put your water filter back together and refill it with clean water.
Tips to Prevent Algae from Growing in Your Water Filter
After cleaning your water filter, prevention is the next step. Here are several steps to minimise the risk of algae in your water filter:
Keep it Out of Direct Sunlight
Store your filter system away from windows and direct sunlight. Algae thrive in light, so a cool, shaded area is ideal.Use an Opaque Cover
If your filter tank is translucent, consider covering it with a dark cloth or towel to block out light.Clean Regularly
Even if algae isn’t currently visible, make it a habit to clean your water filter every few weeks. This will help prevent any early-stage growth that may not yet be visible.Don’t Let Water Sit Too Long
Use the filtered water regularly to keep it fresh. Stagnant water is more susceptible to contamination. If you're going away or won’t use the water for a while, empty the system and allow it to dry.
When to Upgrade Your Water Filter
If you've followed all the cleaning and prevention steps but algae in your water filter keeps returning, it could indicate a more serious issue:
Your current water filter may not be adequate for your water quality.
The system may be too exposed to environmental factors beyond your control.
The filter cartridges may be past their service life and no longer effective.
In any of these situations, upgrading to a more advanced filter system might be your best option. High-performance systems may include additional stages such as activated carbon, silver-impregnated ceramic, sediment pre-filters or UV sterilisation — all of which can help manage microbial contamination more effectively.
Need Help? We’re Here for You
If you’re still unsure what’s causing algae to grow in your water filter or how to fix it, feel free to contact us. Email us a photo, and we'll have a look at it for you.
It might be a sign that this water filter is not sufficient for the contaminants that are in your water. If you purchased through us, we can give you a refund on your water filter and upgrade you to something better, which is our way to try and help.
We want to ensure you're drinking the safest, cleanest water possible because that’s what water filtration is all about.
Seeing algae in your water filter can be surprising, but it’s usually easy to fix and prevent with the right care and placement. Keep your filter clean, out of the sun and make sure it’s suited for your water source.
If all else fails, don’t hesitate to explore a better solution for your home. After all, peace of mind and healthy hydration start with proper water filtration.
Got more questions? Contact us — we’re happy to help.
Why is Algae Growing in My Filter if I Use Town or City Water?
If you're on mains water, the algae likely isn’t coming from the water supply, as it’s typically treated with disinfectants like chlorine. More likely, the algae spores are coming from the surrounding environment, such as air, dust or exposure to sunlight, and are growing in your filter once the disinfectants are removed during the filtration process.
How Often Should I Clean My Water Filter to Prevent Algae?
It’s a good idea to clean your filter system every 2–4 weeks, even if you don’t see algae. Regular cleaning helps prevent the build-up of contaminants and ensures your drinking water stays safe and fresh.
Where Should I Place My Water Filter to Avoid Algae Growth?
Always keep your water filter in a cool, shaded area away from windows and direct sunlight. You can also use a cloth or cover to shield the system from light. Avoid placing it near heat sources like stovetops or appliances.
