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The Maelstrom pre tank filter can be fitted tank top or wall mounted for greater installation flexibility.

Benefits include: 

  • A single point, tank-top filter with a ground breaking U-shaped design.
  • The 180 micron filter screens particles 5 times smaller than is achieved with a standard tank screen.
  • Reduces the hassle of cleaning leaf and debris build-up through Self-flushing.
  • Blocks out light that supports algae growth.
  • Is a versatile product, able to be installed in a variety of pre-tank locations.
  • Reduces frequency and cost of tank cleaning by lowering common sediment build up through cleaner tank water.




Get cleaner water in your tank

Maelstrom On-Tank’s ultra-fine secondary filter removes particles down to 180 microns – 5 times finer than standard rain heads and pre-tank filters. This gives you cleaner, better quality water and lowers the volume of sediment putting pressure on your tank pumps and post-tank filters.


Get more water, faster

Maelstrom On-Tank eliminates the problem of water splashing off your tank inlet screen, especially at high flow rates. Its phenomenal water catchment efficiency (96% at 3,600 litres/hour in wet systems) gives you more water, faster, so you can take full advantage of every raindrop.


Get water effortlessly

Maelstrom On-Tank’s initial 2mm filter diverts leaves and debris which are then flushed out during rainfall events. Because the revolutionary design is low-maintenance with no mechanical parts, it does this with minimal effort from you.


  • Maelstrom Filters filter leaves and debris out of your downpipes with their 2mm bucket, 180 micron filter bag and 0.955 mozzie proof screen. They also minimise splashing to increase the volume of rainwater you harvest.
  • Maelstrom Filters secure the system with the triple layer filtration that prevent insects and other animals from entering and breeding or living in your downpipes.
  • Maelstrom Filters help you Plan for Volume with maximum rainwater capture potential. The ability to capture more water at higher flow rates means you can more easily predict your capture and water usage.


Read more about Pre-tank filtration HERE











Maelstrom Filter

  • How often should I clean my Maelstrom’s filter screens?

    Every environment is different, so the necessary frequency for cleaning your filter screens will vary. We recommend checking your Maelstrom filter regularly after installation to determine the rate at which debris accumulates. You can then use this information to make an informed decision about cleaning frequency. Depending upon your needs and situation, you may determine that cleaning is required monthly, quarterly, after each heavy downpour, or at a different frequency.

    Do I need to modify the tank inlet when installing my Maelstrom?

    No. Your Maelstrom is supplied with an adjustable flange that is designed to accommodate existing 300mm, 400mm and 500mm inlets. Simply remove the existing tank screen and trim the flange to suit the size of your inlet hole.

    What head height is required when installing my Maelstrom on the inlet side of a wet or “charged” system?

    Your Maelstrom filter should be installed no less than 500mm above the inlet of the tank.
    When the Maelstrom overflow is connected to an outlet, for example, a stormwater discharge, the wet system head height can be reduced to accommodate low head systems. Collection efficiency is traded-off against low head height filtration.

    What is the Maelstrom’s maximum flow rate?

    On a wet rain harvesting system, your Maelstrom can handle water flowing at 10 litres (2.64 gallons) per second with a water catchment efficiency of 96%. It can handle water flowing at 5 litres (1.32 gallons) per second with a 99% water catchment efficiency for wet systems. Above 10 litres (2.64 gallons) per second, your Maelstrom will direct excess water to the outlet port (overflow).

    Used in a wet rain harvesting system, your Maelstrom will yield 99% filtered water catchment at 5L/sec and 96% filtered water catchment at 10L/sec.

    Are replacement filter bags available?

    Yes. Replacement filter bags are available for your Maelstrom filter. The Maelstrom bag is designed to be reusable and can be washed and reinstalled. In the unlikely event that your bag is damaged or lost, replacements are available from Blue Mountain Co.

    Can I connect multiple pipes or “lines” to my Maelstrom?

    Multiple pipes can be consolidated before they reach your Maelstrom filter. However, it is important to assess the impact of consolidating these pipes to ensure that your total system flow is not restricted.

    Can I install 90mm pipe to my Maelstrom?

    Yes. You can use a tapered reducer or LIT (level invert taper) to connect 90mm pipe to your Maelstrom’s DN100mm inlet and outlet ports.

    Can I install inlet pipes to both side ports so I have two inlets rather than one inlet and one outlet?

    No. We do not recommend installing inlet pipes to both side ports. It is important that one side port is dedicated to overflow to allow your Maelstrom to perform its self-cleaning function and prevent clogging.

    Can I install a first flush before my Maelstrom?

    Yes. First flush diverters can be installed before or after your Maelstrom filter. If you choose to install a first flush diverter upstream of your Maelstrom, make sure you install a screened rain head before the first flush diverter so it cannot be clogged with leaves and larger debris.

    Can the Maelstrom be installed in the charged area of a charged system? Ie. Can the Maelstrom be positioned below the inlet of the rainwater tank.

    No. Your Maelstrom filter is not designed to carry a head of water, as the filter uses a self-cleaning gravity feed action to discard debris from the flow of water.

    However, you can install your Maelstrom filter on top of your tank in place of your tank screen (or beside your tank) as the final filtering point for your wet system.

    What do I do if there is a significant amount of water coming out of the debris overflow of the Maelstrom?

    Check the following:

    • Check the blue internal filter if there is a large amount of debris
    • Check the fine bag filter if there is a lot of fine debris
    • Clean either of the above filters if required

    If the rainfall event is extreme, it is possible for some unfiltered water to overflow from the debris overflow port. Refer to expected flow rates section.

    How do I collect the maximum amount of water from my Maelstrom?

    The best way to maximise the amount of captured water from the Maelstrom is to:

    • Ensure the filters are maintained periodically
    • An alternative setup for the debris overflow to maximise clean water catchment is to add a small upwards bend, which will help to slow the flow of water at the debris overflow – forcing the water through the Maelstrom’s filters. In this scenario, it is recommended to maintain your filters more regularly since the debris is forced to flow over the bend.
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