Quick Summary: A cistern glossary defines key terms for rainwater harvesting systems, helping you understand components like tanks, filters, and pumps for efficient water collection and storage. Knowing these terms empowers you to maintain your system and use collected water safely.
Ever felt a little lost when talking about water tanks, filters, or the bits and bobs that make a rainwater harvesting system hum? You’re not alone! Many homeowners are discovering the benefits of collecting rainwater, but the technical terms can sound like a foreign language. This can make choosing, installing, or even just thinking about a cistern system feel a bit overwhelming. But don’t worry, we’re here to break it all down. Understanding the basic language of cisterns is the first step to confidently managing your own water supply, saving money, and helping the environment. Let’s dive in and demystify those terms!
Unlocking Your Cistern System: A Beginner’s Glossary
As homeowners, we’re increasingly looking for smart, sustainable ways to manage our resources. Rainwater harvesting is a fantastic option, offering a way to conserve water and reduce utility bills. However, diving into this world can feel like learning a new language. From the largest tanks to the smallest fittings, each part has a name and a purpose. This glossary is designed to be your friendly guide, breaking down the essential terms you’ll encounter when exploring, installing, or maintaining a cistern system. Think of it as your cheat sheet to becoming a rainwater harvesting pro!
Why Does Understanding Cistern Terms Matter?
Knowing the right words for different parts of a cistern system is more than just a vocabulary lesson. It’s about practical application!
- Better Decision-Making: When you understand what a “first flush diverter” or a “downpipe filter” does, you can make informed choices about which components you need.
- Easier Maintenance: If your system needs a tune-up, knowing the names of parts helps you communicate with professionals or even tackle simple DIY fixes yourself.
- Improved Safety: Understanding how different parts work together ensures your system is installed and operated safely, protecting your home and family.
- Enhanced Efficiency: Knowing the function of each component helps you optimize your system for the best water collection and usage.
- Confidence Building: No more nodding along when a plumber uses jargon! You’ll feel more confident discussing your system and your needs.
The Core Components: Tanks and Their Friends
At the heart of any rainwater harvesting setup is the tank, where all that precious rain is stored. But it’s not just about the big container; several other components work to get the water from your roof into the tank and then to where you need it.
1. Cistern / Rainwater Tank
This is the main storage vessel for collected rainwater. Cisterns can be made from various materials like plastic (polyethylene), fiberglass, concrete, or metal. They come in many shapes and sizes, from small above-ground units to large underground installations. The choice often depends on available space, budget, and local regulations. For a deeper dive into tank types, the EPA’s Rainwater Harvesting Manual offers comprehensive information.
2. Catchment Area
This is the surface where rain falls and is collected. Typically, this is your roof. The material of your roof can affect water quality, with some materials being more suitable than others. Smooth, non-toxic roofing materials are best for drinking water systems, though for garden use, most common roofing materials are acceptable.
3. Gutters and Downpipes (Downspouts)
These are essential for directing rainwater from your roof to your storage system. Gutters run along the edge of your roof, collecting water, and downpipes carry it down to the ground level, where it can then be channeled into your cistern or a filtration system.
4. Leaf Guards / Gutter Screens
These are mesh or plastic covers that fit over your gutters to prevent leaves, twigs, and other debris from entering. They help reduce clogging and the amount of organic matter that makes its way into your system, improving water quality and reducing maintenance.
5. Downpipe Filter / Gutter Filter
Installed in the downpipe, these filters are designed to remove finer debris like grit, pollen, and smaller organic matter before the water reaches the cistern. They are a crucial step in pre-filtering the water, especially if it’s intended for household use.
6. First Flush Diverter
This clever device diverts the initial flow of rainwater, which often contains the most contamination (dust, bird droppings, pollen, etc.) from the roof. After the first flush, the diverter automatically allows cleaner water to pass through to the cistern. This significantly improves the quality of stored water.
7. Overflow Pipe
When your cistern is full, any excess water needs a place to go. The overflow pipe provides a safe outlet for this water, preventing the tank from becoming damaged or overflowing in unintended areas.
Getting Water to You: Pumps and Plumbing
Once the water is safely stored, you’ll likely want to use it. This is where pumps and plumbing come into play, ensuring you have access to your collected rainwater when you need it.
8. Submersible Pump
This type of pump is designed to be placed directly inside the water within your cistern. It pushes water up and out through your plumbing system. They are often quieter and more efficient than external pumps for this application.
9. Surface Pump / Jet Pump
These pumps sit outside the cistern, typically above ground or on a stable base. They draw water out of the tank. Jet pumps use a venturi system to create suction. They can be a good option for smaller systems or where access for maintenance is a consideration.
10. Pressure Tank
Often used in conjunction with a pump, a pressure tank helps maintain consistent water pressure in your system. It stores a small amount of water under pressure, reducing the frequency with which the pump needs to cycle on and off, thus prolonging its life.
11. Water Level Indicator
This is a gauge or sensor that tells you how much water is currently in your cistern. It can be a simple float system, an electronic sensor, or even a visual marker on the outside of the tank. Essential for knowing when to conserve and when you have plenty of water.
12. Inlet Screen
A coarse screen placed at the point where water enters the cistern. It acts as the first line of defense against larger debris like leaves and insects, preventing them from entering the tank itself.
Keeping it Clean: Filtration and Treatment
Depending on how you plan to use your harvested rainwater, you might need additional filtration and treatment steps to ensure it’s safe and clean. Here’s a look at common systems and components:
13. Sediment Filter
These filters are designed to remove suspended particles like sand, silt, and rust from the water. They are often the first stage of filtration after the water leaves the cistern and before it goes to a point of use or further treatment.
14. Carbon Filter
Activated carbon filters are excellent at removing chlorine, odors, bad tastes, and certain organic compounds from water. They are often used as a secondary filter after sediment filters to improve water palatability and clarity.
15. UV Sterilizer (Ultraviolet Treatment)
This is a crucial step for making rainwater safe for potable (drinking, cooking) use. UV sterilizers use ultraviolet light to kill bacteria, viruses, and other harmful microorganisms without adding chemicals. The water must be clear (free of sediment and other particles) for UV light to be effective.
16. Chlorine/Bromine Disinfection
In some cases, especially for potable water systems and where UV is not used or as a backup, chemical disinfection using chlorine or bromine might be employed. This kills pathogens but can affect the taste and requires careful monitoring of dosage.
Types of Cisterns and Their Placement
Beyond the basic components, the type and location of your cistern also have specific terminology. Understanding these can help you plan your system effectively.
17. Above-Ground Cistern
These tanks are installed on the surface, either on a prepared base or sometimes directly on the ground (though a solid foundation is recommended for stability). They are generally easier to install and maintain but take up visible space and can be more susceptible to temperature fluctuations.
18. Underground Cistern (Buried Cistern)
Installed beneath the ground, these tanks save surface space and help keep water cooler, which can reduce algae growth. Installation is more complex and costly, often requiring excavation and professional backfilling. They must be designed to withstand soil pressure.
19. Freestanding Cistern
This term often refers to above-ground tanks that are not part of a building’s structure and can be placed anywhere on the property, provided there’s a suitable foundation.
20. Gravity-Fed System
In some setups, if the cistern is located at a higher elevation than the point of use (e.g., a raised house or a strategically placed elevated tank), gravity can be used to distribute water without a pump. This is the most energy-efficient method but requires specific site conditions.
21. Atmospheric Collector
While not a traditional cistern, this term refers to systems that collect water directly from the air’s humidity, such as fog nets or dew collectors. These are typically used in very specific climates where traditional rainfall is scarce.
Ancillary & Maintenance Terms You Should Know
Beyond the main functional parts, various other terms relate to the upkeep and overall operation of your cistern system.
22. Sump
A pit or reservoir that collects water and is equipped with a pump (a sump pump) to automatically remove it. In a cistern context, a sump might be at the very bottom of the tank to collect any sediment before it’s pumped out with the water, protecting the pump.
23. Inlet
The point where water enters the cistern. This is typically connected to your downpipes via a filtration system.
24. Outlet
The point where water is drawn from the cistern to be used, usually connected to your pump or the gravity feed line.
25. Scum Layer / Floating Debris
A layer of lighter organic matter that can form on the surface of stored water. While some systems are designed to draw water from below this layer, it’s a sign of organic material entering the tank.
26. Sludge / Sediment Layer
Heavier particles that settle at the bottom of the cistern. Regular cleaning is needed to remove this buildup, which can affect water quality and potentially damage pumps.
27. Cistern Cleaning
The process of regularly emptying, cleaning, and disinfecting the cistern to remove accumulated sludge, sediment, and any potential contaminants. This is crucial for maintaining water quality and system longevity. The NSF/ANSI 61 standard is often referenced for materials used in contact with drinking water, important for tank and component selection.
28. Water Hauling
The process of transporting water to your cistern, typically by a truck, if your collected rainwater supply runs dry. This is a backup measure when natural rainfall is insufficient.
Comparing Cistern Types: A Quick Look
Choosing the right cistern involves weighing different factors. Here’s a simplified comparison:
| Cistern Type | Pros | Cons | Ideal For |
|---|---|---|---|
| Above-Ground (Plastic/Fiberglass) | Lower cost, easy installation, portable, visible water level | Takes up space, can be unsightly, water temperature fluctuates, potential UV degradation over time | Gardening, non-potable uses, smaller homes, renters |
| Underground (Concrete/Plastic) | Saves space, keeps water cool (less algae), protected from UV, aesthetically pleasing | High installation cost, complex installation, harder to access for cleaning/repairs | Larger homes, potable water systems (with proper treatment), limited yard space |
| Above-Ground (Metal) | Durable, can be aesthetically pleasing (modern designs) | Can be expensive, potential for corrosion if not treated, can be noisy in rain | Homes where aesthetics are a priority, larger capacity than plastic tanks |
Putting It All Together: Your Cistern Journey
Understanding these terms is your starting point for a successful rainwater harvesting system. Imagine you’re building a puzzle; each piece (term) helps you see the bigger picture (your efficient water system). Whether you’re just curious or ready to install, this glossary should make the process less daunting.
| Component | Primary Function | Importance Level for Basic System |
|---|---|---|
| Cistern/Tank | Stores collected rainwater | Essential |
| Catchment Area (Roof) | Collects rainwater | Essential |
| Gutters & Downpipes | Directs water from roof to storage | Essential |
| Leaf Guards | Prevents large debris from entering gutters | Highly Recommended |
| First Flush Diverter | Removes initial contaminated water | Highly Recommended (for better quality) |
| Inlet Screen | Filters debris entering tank via inlet | Recommended |
| Overflow Pipe | Safely removes excess water | Essential |
| Submersible/Surface Pump | Moves water from tank to use points | Essential (for most systems) |
| Pressure Tank | Maintains consistent water pressure | Recommended (for pump longevity) |
| Sediment Filter | Removes small particles, pre-filtration | Recommended (if using water for anything other than basic irrigation) |
| UV Sterilizer | Kills bacteria/viruses for potable use | Essential (for drinking/cooking) |
Frequently Asked Questions (FAQ)
What is the most important part of a cistern system for a beginner?
For a beginner, the most crucial parts are the cistern (tank) itself and the gutters and downpipes to get water into it, along with an overflow pipe. These ensure you can collect and store water safely.
Do I really need a first flush diverter?
While not strictly essential for simply collecting water, a first flush diverter is highly recommended. It significantly improves the quality of the water stored in your cistern by diverting the initial, most contaminated runoff, meaning less cleaning and better water later on.
Can I drink water directly from my cistern?
Generally, no. Rainwater collected from roofs can contain contaminants like bird droppings, pollen, and atmospheric pollutants. To make it safe for drinking (potable use), it requires thorough filtration and a UV sterilizer or chemical disinfection. Always consult local health guidelines.
How often do I need to clean my cistern?
The frequency of cistern cleaning depends on your location, the quality of your catchment area, and how well your pre-filtration (leaf guards, first flush diverters) works. A good rule of thumb is to inspect it annually and clean it every 2-5 years. Sediment buildup is the main concern.
What’s the difference between a cistern and a water tank?
The terms are often used interchangeably, but “cistern” traditionally has referred to a tank that stores rainwater or water intended for domestic use, often built underground. “Water tank” can be a more general term for any container holding water, including for industrial or agricultural purposes. For rainwater harvesting, they are essentially the same thing.
Can I use a regular plastic barrel as a cistern?
Yes, food-grade plastic barrels can be a cost-effective way to start collecting rainwater, especially for garden use. Ensure they are clean, opaque (to prevent algae growth), and have a secure lid. They are best suited for smaller volumes and non-potable applications.