That iridescent or oily-looking film shimmering on the surface of your rain barrel water is likely biological in nature, often formed by harmless bacteria or algae, but occasionally indicative of more serious issues. While usually not cause for alarm, understanding the cause of this film is crucial for ensuring the safety and usability of your harvested rainwater.
Decoding the Film: What is It?
The film you see can be composed of a few different elements. The most common culprit is iron bacteria. These bacteria oxidize dissolved iron in the water, creating a metallic sheen. While they don’t typically pose a health risk, they can impart a metallic taste and odor to the water, making it less appealing for certain uses.
Another frequent contributor is biological growth, particularly algae or bacteria. Algae can create a green or brown film, while bacteria can form a clear, oily-looking slick. These growths thrive in standing water, especially when exposed to sunlight. Dust, pollen, and decaying organic matter that collect in the rain barrel serve as food sources, fueling this biological activity. The decomposition of organic material can also create a film of tannins, which are naturally occurring organic compounds.
Finally, though less common, the film could indicate contamination with hydrocarbons (oil or grease) or other pollutants washed off your roof. This is a more serious concern and requires immediate investigation. The presence of these contaminants is particularly likely if your roofing material is old, deteriorating, or treated with certain chemicals.
Identifying the Source: Visual Clues and Tests
Observing the characteristics of the film is the first step in identifying its source. An iridescent sheen that breaks apart into distinct patterns when disturbed is often indicative of iron bacteria or biological growth. A persistent, oily sheen that doesn’t break apart easily could signal hydrocarbon contamination.
While a visual inspection can provide clues, a water test is the most reliable way to determine the source and severity of the problem. Test kits are available for identifying bacteria, iron, and various contaminants. Consulting with a local water quality testing lab can provide a more comprehensive analysis.
Rain Barrel Film FAQs:
Here are some frequently asked questions that will provide even more detail to the mysterious film in your rain barrel.
FAQ 1: Is the film always harmful?
No. In most cases, the film is not harmful and is simply the result of natural processes. Biological growth, such as algae and iron bacteria, is common in rain barrels and often poses no significant health risk for uses like watering plants. However, if you suspect hydrocarbon contamination, the water should not be used for any purpose until it has been tested.
FAQ 2: Can I still use the water for my garden?
Generally, yes. Water with a film caused by algae, bacteria, or iron is usually safe for watering plants. However, avoid using it on edible plants if you suspect contamination or if the water has a noticeable odor or discoloration. Consider watering at the base of the plants to minimize contact with edible parts.
FAQ 3: How do I prevent the film from forming in the first place?
Prevention is key. Here are several strategies:
- Clean your gutters regularly: This prevents debris from entering the rain barrel.
- Use a screen filter: Install a screen filter on your downspout to catch leaves, twigs, and other large particles before they enter the barrel.
- Choose an opaque rain barrel: Sunlight fuels algae growth, so an opaque barrel will help limit its formation.
- Elevate your rain barrel: Elevating the barrel can improve drainage and prevent sediment buildup.
- Add mosquito dunks: These contain Bacillus thuringiensis israelensis (Bti), which kills mosquito larvae and can also help control algae growth.
- Regularly empty and clean the barrel: Completely empty and scrub the barrel at least twice a year.
FAQ 4: What is the best way to clean my rain barrel?
Empty the barrel completely. Use a stiff brush and a solution of mild soap and water to scrub the inside surfaces. Rinse thoroughly with clean water. Avoid using harsh chemicals or bleach, as they can be harmful to the environment and may damage the barrel. A pressure washer can also be effective, but be careful not to damage the barrel.
FAQ 5: Does sunlight affect the formation of the film?
Yes, sunlight plays a significant role. Sunlight provides the energy needed for algae and other photosynthetic organisms to grow. Reducing sunlight exposure is crucial for preventing film formation.
FAQ 6: What are the signs of hydrocarbon contamination?
Look for a persistent, oily sheen that doesn’t break apart easily. The water may also have a noticeable gasoline or oily odor. If you suspect hydrocarbon contamination, do not use the water and contact your local environmental agency for guidance on proper disposal.
FAQ 7: Are there any natural remedies for preventing film formation?
Copper is known to inhibit algae growth. Some people place copper strips or a small piece of copper pipe inside their rain barrels. However, use caution, as excessive copper can be harmful to plants. Beneficial bacteria products can also be added to outcompete the organisms forming the film.
FAQ 8: How often should I empty and clean my rain barrel?
Aim to empty and clean your rain barrel at least twice a year, ideally in the spring and fall. If you notice excessive film formation or debris buildup, you may need to clean it more frequently.
FAQ 9: What type of filter is best for my rain barrel?
A downspout filter is the most effective way to prevent debris from entering the rain barrel. These filters are installed directly on the downspout and capture leaves, twigs, and other large particles. Internal filters, which are placed inside the rain barrel, can also be helpful for removing smaller particles.
FAQ 10: Can the film affect the water pressure from my rain barrel?
While the film itself doesn’t directly affect water pressure, excessive debris buildup inside the barrel can clog the outlet and reduce water flow. Regularly cleaning the barrel and using a filter will help maintain optimal water pressure.
FAQ 11: Are there different types of rain barrels that are less prone to film formation?
Opaque rain barrels are less prone to algae growth than transparent barrels. Some rain barrels also have features like built-in filters or overflow valves that can help prevent debris buildup and improve water quality.
FAQ 12: What if I’m still unsure about the safety of the water?
When in doubt, err on the side of caution. If you are unsure about the safety of the water, do not use it for drinking, bathing, or watering edible plants. Contact your local health department or a water quality testing lab for further assistance. Getting a professional analysis will offer peace of mind and allow you to confidently use your rain barrel water.
Taking Action: Ensuring Safe and Usable Rainwater
The presence of a film on your rain barrel water is a common occurrence. By understanding the potential causes, implementing preventative measures, and conducting regular maintenance, you can minimize film formation and ensure that your harvested rainwater is safe and usable for a variety of purposes. Remember to prioritize water testing if you suspect contamination and always err on the side of caution when determining the appropriate uses for your rainwater. Proper care and monitoring will transform your rain barrel from a potential problem source to a valuable resource.