Manage Standing Water | Rain Harvesting Steps | BMCo

standing water

Harvesting high quality water is half the Rain Harvesting battle won. However, if you want your rainwater supply to remain reliable and fit-for-purpose, you also need to maintain the quality of the water you’ve harvested. Managing your standing water to prevent and limit hidden activity in your pipes and tanks is central to achieving this.

Managing standing water involves taking steps to prevent algae growth and sediment resuspension, plus draining “charged lines” if you have a wet Rain Harvesting system. Taken together, these measures help ensure you can enjoy cleaner rainwater and lots of it day in and day out.

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In particular, we recommend doing all you can to account for challenges posed by:


Vegetation         Unwelcome Intruders

Fine Particles      Hidden Activity


Prevent sediment resuspension

Sediment resuspension occurs when the sediment that rests on your tank floor is stirred up by water flow. As such, the first step in preventing sediment resuspension is to limit the volume of sediment that ends up in your tank by applying steps three and four  – filtering leaves and debris, and diverting the first flush.

Of course, even with the most thorough filtering, some sediment will end up in your tank. Automatic tank vacuums offer an effective way to manage this sediment. These units draw up sediment from the bottom of your tank so that when your tank overflows, it expels the most sediment-laden water, rather than the cleaner water on top.

As an added precaution, vent cowls can be used to promote ventilation in the tank. This increases the oxygen content in your stored rainwater, helping to prevent stagnation.

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Drain “charged lines” in wet systems

In wet Rain Harvesting systems, water-filled pipes (also known as “charged lines”) create the perfect environment for anaerobic fermentation. Draining these charged lines after each rainfall event is a simple and effective way to prevent standing water fouled by this hidden process from contaminating the rainwater in your tank.

First flush in-ground diverters, flow controllers and sliding gate valves can all be used to drain charged lines. First flush in-ground diverters automatically divert and capture the water from your water-filled pipes after it rains, effectively transforming your wet system into a dry system. Similarly, flow controllers can be programmed to automatically drain the water from your pipes, while sliding gate valves are a manual option that achieves the same end result.

Prevent algae growth

Algae growth and sediment resuspension can both threaten the quality of the rainwater in your tanks.

Algae thrives in sunlit water, so to prevent algae growth, you need to keep sunlight out of your tank. This can be done by installing a solar cover over your tank inlets. Maelstrom filters can also be used to keep sunlight out of your tank inlets, as the units are fully enclosed.

Products that can help

First Flush Diverters
First Flush Diverters
Vent Cowls
Vent Cowls
Tank Screens and Solar Shields
Tank Screens and Solar Shields
Wet/Dry Valve
Wet/Dry Valve

Find out more about applying the 8 Rain Harvesting Steps


Download the
Rain Harvesting Handbook


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