We generally classify dams of 1 acre (approximately 4,050m²) or more as large dams.

Once a dam gets to this size, aeration becomes more about designing the right system than simply choosing a larger motor. The dam's depth, shape, number of separate areas, islands, nutrient levels, water use and available power can all affect the design.

For dams around 5 acres and above, we may treat the project as a mega-dam application and look at larger or multiple aeration systems.

Most activity in a waterbody happens within a metre of two of the surface and on the bottom. This is where the organisms tend to live and where most aeration needs to be focused. So for ease, we focus on surface area more than volume when sizing up an aerator. 

The best thing to do is get a FREE recommendation. Fill in this Dam Diagnostics form and I'll look at your dam on Google Maps and provide advice. If you have an aerator in mind, feel free to mention this in the comments box. The truth is we double check every enquiry that comes in anyway, so even if you make a choice on a motor size, we'll double check it's the right fit for your conditions.

Hakko is likely to be the most affordable option in this setup if you have shallow water, less than 2m deep. If you have water deeper than 2m, Matala is likely to be the lowest cost option. 

There isn't one aerator that is right for every large dam.

We look at factors including:

• Surface area
• Water depth
• Dam shape
• Number and location of deeper areas
• Islands or other obstructions
• Nutrient levels
• Existing water-quality problems
• Whether the dam is used for swimming, irrigation, livestock or recreation
• Available mains power
• Whether solar, wind or another off-grid option is required

From there, we can determine whether a surface aerator, sub-surface aerator, multiple aerators or a combination of systems makes the most sense.

For larger or more complex dams, getting the layout right can be just as important as choosing the motor size.

That depends on the dam.

For large dams, we commonly consider systems such as Air-O-Lator surface aerators, Matala sub-surface aerators and Vertex sub-surface aerators. Larger Vertex systems can be configured for waterbodies exceeding 20 acres.

Surface and sub-surface aerators work differently, so the best choice depends on what you are trying to achieve.

If the dam is deep and requires extensive mixing throughout the water column, sub-surface aeration can be very effective. If rapid oxygenation and strong surface mixing are priorities, a surface aerator may be more appropriate.

Both can be effective.

Surface aerators are particularly useful when you want rapid oxygen transfer and strong surface mixing. They are also an option where you want a visible fountain-style aerator.

Sub-surface aerators use a compressor on the bank to push air through diffusers positioned on the bottom of the dam. They are particularly useful in deeper water and can provide extensive circulation while using relatively low power.

For some large dams, the best solution is to combine surface and sub-surface aeration rather than choosing one or the other.

Sometimes, but not always.

As a dam gets larger, a single aerator may not provide adequate coverage across the entire waterbody. Multiple aerators or multiple sub-surface air stations can be used to distribute aeration across different areas.

The layout matters because the effective circulation area of an air station is influenced by its depth and what surrounds it. Islands, shorelines and irregular shapes can restrict circulation.

For larger dams, we can design the system around the actual shape of the waterbody rather than simply assuming one unit will be enough.

There is no fixed number based solely on acreage.

The number of aerators or air stations depends on the size and shape of the dam, its depth, the aerator being used and the water-quality problem you are trying to address.

For example, a long, narrow dam may require a different arrangement from a roughly circular dam of the same surface area. Islands and multiple deep areas can also change the recommended layout.

For large projects, we can work out the number and positioning of air stations as part of the system design.

Air stations should generally be positioned in the deeper areas of the dam, but the exact locations matter.

An air station creates an area of circulation that can be thought of as an inverted cone. The deeper the air station, the greater the area of water it can influence at the surface.

However, shorelines, islands and unusual dam shapes can interrupt that circulation. This is why simply placing diffusers at evenly spaced intervals isn't always the best approach.

For a large or irregular dam, we can recommend the number and exact positioning of the air stations as part of the system design.

No, but depth affects which type and size of aerator is most appropriate.

The large-dam systems on our site are generally designed around water deeper than 2m, with deeper water particularly well suited to sub-surface aeration. Water less than 2m deep can still be aerated, but the conditions are less ideal and a larger unit may be required.

If your large dam is relatively shallow, we would size the system around the actual conditions rather than applying a standard large-dam package.

For aerator sizing, we generally start with the surface area of the dam.

A simple calculation is:

Average length × average width = surface area in square metres

To convert square metres to acres, divide by 4,050.

For example:

4,050m² ÷ 4,050 = 1 acre

For irregular dams, this calculation is only an approximation. We can also assess the dam using mapping and other information to help determine the appropriate system.

Surface area gives us a practical starting point for aerator sizing.

Aeration needs are not determined simply by how many litres of water are in a dam. Depth, shape and where the water is being mixed all affect how an aerator performs.

For that reason, we generally start with the surface area and then consider depth and the other characteristics of the dam before selecting the system.

Yes. Stratification occurs when the water separates into layers with different temperatures and oxygen levels. The deeper water can become oxygen depleted, particularly when there is a high organic or nutrient load.

Sub-surface aeration is particularly useful for mixing deeper water and helping to break down this separation.

For example, we have supplied a Vertex system with five quad-disc air stations for a 6+ acre lake experiencing stratification, low dissolved oxygen, odours and algal blooms.

Yes. Increasing oxygen transfer is one of the main purposes of aeration.

Surface aerators bring oxygenated water into contact with the atmosphere, while sub-surface systems create rising columns of bubbles that move and mix water through the dam.

The amount of oxygen added depends on the aerator, water conditions, depth, temperature and system design, so we don't recommend sizing a system from acreage alone.

Aeration can be an important part of managing algae, particularly where low dissolved oxygen, stratification and nutrient-rich conditions are contributing to poor water quality.

However, aeration isn't a magic switch for algae. Nutrients are a major driver of algae, so if a large dam has a significant nutrient load, aeration may need to be combined with biological or nutrient-management strategies.

The right approach depends on what is actually driving the algae problem.

It can form part of a broader water-quality strategy, but aeration shouldn't be treated as a standalone aquatic weed killer.

Aeration improves oxygenation and mixing and can support a healthier biological environment. If weeds are already established, however, the appropriate approach may also involve nutrient management, biological treatments or targeted aquatic weed treatment.

For large dams, we recommend looking at the underlying conditions rather than treating the visible weed growth in isolation.

Aeration can help create more oxygen-rich conditions around the bottom of a dam, which supports aerobic biological activity.

Where a dam has substantial organic sludge, aeration can be particularly useful when combined with appropriate biological treatments such as Biostim.

The result depends on how much sludge is present, what it is made of and the overall nutrient load of the dam.

It can. Persistent odours can be associated with low-oxygen conditions and the decomposition of organic material. Aeration introduces oxygen and improves circulation, helping shift the water towards more aerobic conditions.

If a large dam has a significant organic or nutrient load, we may also recommend biological treatment alongside aeration.

Yes, and sub-surface aeration can be particularly attractive for swimming dams because the electrical equipment remains on the bank.

With a sub-surface system, the compressor is positioned on land and air is pumped through hose to the diffusers in the water. There is no powered motor sitting in the water.

Vertex specifically promotes its systems for swimming dams for this reason.

Yes. We offer solar options for both surface and sub-surface aeration. Matala and Vertex sub-surface systems can be converted to solar using a purpose-built solar drive, while several Air-O-Lator surface aerators are also available in solar configurations.

Solar can be particularly useful when the dam is a long way from mains power.

Yes. Depending on the site, options can include solar, wind or remote mains-powered systems.

For example, Matala and Vertex systems can be installed as remote setups when mains power is within approximately 200m of the waterbody. The compressor can remain near the power source while air is delivered to the dam through buried hose.

For genuinely off-grid sites, solar or wind-powered systems may be more appropriate.

Yes, although wind-powered systems have their own limitations.

The OWS Windmill Aerator is designed as an off-grid sub-surface aeration system and is available in configurations for dams up to around 2 acres. For larger dams, multiple systems or another aeration technology may be more appropriate.

The amount of wind available at the site is also an important consideration.

It depends on the shape and requirements of the dam.

Several strategically positioned aerators can sometimes provide better coverage than one very large unit, particularly where the dam is long, irregular or has islands or separate deep areas.

On the other hand, a larger system may be more appropriate where a single compressor can efficiently supply multiple air stations.

We design the system around the waterbody rather than automatically choosing one approach.

Yes. For deep or particularly demanding waterbodies, combining surface and sub-surface aeration can provide the advantages of both approaches.

A surface aerator can provide rapid oxygenation and strong surface mixing, while sub-surface diffusers can circulate deeper water and help address stratification.

The combination needs to be designed properly so the different systems complement rather than duplicate each other.

Yes, in many cases. A properly planned system can often be expanded by adding additional air stations, compressors or aerators.

This is worth considering when a dam is being developed in stages, when water use is changing or when additional areas of the dam may need to be brought into the aeration zone later.

If future expansion is likely, tell us when you enquire so we can design with it in mind.

Not necessarily. The appropriate operating schedule depends on the aerator, the waterbody and the reason for aeration.

Some systems are designed for continuous-duty operation, while timers can also be used where an operating schedule is appropriate.

For a large dam with significant water-quality problems, we would recommend an operating schedule based on the actual conditions rather than using a generic timer setting.

There isn't a meaningful single price for a large-dam aeration system.

The cost depends on the size of the dam, aerator type, motor size, number of air stations, hose length, power supply and installation requirements.

As the system becomes larger, the design and installation can become just as important as the aerator itself.

The best way to get an accurate price is to provide us with your dam details so we can recommend an appropriately sized system.

Yes. Custom system design is a normal part of what we do.

For a large dam, we can design the system around the actual waterbody, including the type and size of aerator, number and position of air stations, hose lengths, power source and installation requirements.

We can also design systems using multiple aerators or a combination of surface and sub-surface aeration where appropriate.

For very large waterbodies, Vertex also provides design tools that can be used to calculate pump size, air-station locations, hose requirements and estimated water movement.

Yes. We provide installation services, particularly around Melbourne, and travel for larger project work. Where appropriate, we can also help connect customers with local installers.

For large projects, installation can include positioning the aerator, laying and securing weighted hose, installing air stations, setting up controls and commissioning the system.

Yes. We can help with ongoing maintenance as well as the original system design and installation.

The maintenance requirements depend on the type of aerator. Sub-surface systems generally allow the compressor to remain onshore, making servicing straightforward, while the air stations themselves require relatively little maintenance.

For Vertex systems, for example, the air stations are designed to be essentially self-cleaning, although periodically forcing additional airflow through individual stations is good practice.

The more information we have, the more accurately we can size and position the system.

Useful information includes:

• Approximate dam size or surface area
• Maximum and average depth
• Dam shape
• Location of islands or separate sections
• Whether the dam is used for swimming, irrigation, livestock or recreation
• Current problems such as algae, odour, sludge or low oxygen
• Available mains power
• Distance from the dam to the nearest power supply
• Whether solar or another off-grid option is preferred

If you aren't sure of the measurements, that's fine. Start with our Dam Diagnostics form and we'll help work out what is required.

That's exactly when professional sizing becomes important.

The standard aerator recommendations are based on relatively straightforward conditions. A shallow dam, irregular shape, islands, unusually high nutrient levels, multiple deep areas or other complications can all change the appropriate system.

Rather than simply selecting an aerator from a table, we can look at your individual dam and recommend a system around its actual conditions.

The easiest way is to have the dam assessed before buying the equipment.

Fill in the Dam Diagnostics form and tell us what you're trying to achieve. We'll look at the size, shape and conditions of your dam and recommend the appropriate aeration approach.

You don't need to know whether you need a ¾hp, 1hp, 3hp or 4hp system before contacting us. That's our job.

Yes, we do.  Typically for customers close to Melbourne but we do travel for project work and may also be able to refer you to a local installer if we know of one in your area. Please reference this in your enquiry and we can provide an idea of the cost. We also have installation videos for those who want to go it alone.