The first step in any rainwater harvesting system is the collection surface — typically your roof. The material of the roof will affect the quality and quantity of the water collected.

Roof Materials:

Colorbond or Zincalume Steel – Commonly used in New Zealand, both are excellent for rainwater collection since they are non-porous, durable, and easy to clean.

Tile or Slate – These can be used, but ensure they are clean and free of debris, as they can sometimes leach chemicals.

Metal Roofing – Ideal for capturing rainwater, as it doesn't leach harmful substances and is relatively low-maintenance.

Best Practices:

Keep your roof clean, as it’s the primary source of contamination if not maintained.

Regularly clean gutters and downspouts to prevent build-up of dirt, leaves, or bird droppings.

Consider installing a first flush system (see below) to divert initial runoff, which can be contaminated with debris or pollutants from the roof.

A properly designed gutter and downspout system ensures that rainwater flows efficiently from the roof to your storage tank(s) without clogging.

Key Components:

Gutters: These should be wide enough to handle heavy rainfall and direct the water to the downspouts.

Downspouts: These need to be sturdy and capable of carrying water to the storage tank. Consider using screened or mesh filters at the downspouts to catch large debris like leaves or twigs.

Leaf Guards or Screens: To prevent leaves, debris, and birds from clogging the gutters and affecting water quality.

A first flush diverter is an essential part of any rainwater harvesting system. It prevents the first batch of rainwater (which is typically contaminated with dirt, dust, leaves, and other pollutants) from entering your tank.

How it works:

The first flush system diverts the initial flow of water into a separate container or drain.

Once the contaminants are flushed away, the rest of the clean water is directed into the storage tank.

Popular Systems:

Simple First Flush Diverter: A small, inexpensive device attached to the downspout that directs initial runoff away from the tank.

Automatic First Flush Diverter: More advanced systems that automatically release the first flush once the water reaches a set level.

Your water storage tank is where the rainwater is held for later use. The size and type of tank will depend on your household’s water needs, the climate, and the amount of rainfall in your area.

Types of Tanks:

Polyethylene (Plastic) Tanks: Common in New Zealand, these are durable, UV-resistant, and relatively affordable. They come in various sizes (from 1000L to 30,000L).

Stainless Steel Tanks: These are long-lasting, but generally more expensive. They’re less prone to algae growth and are better for long-term storage.

Concrete Tanks: Often used in more permanent installations, but they require a solid foundation and can be expensive. They also can be prone to cracking.

Underground Tanks: These are great for saving space, especially in tiny homes, and they keep the water cooler. However, they can be more expensive and difficult to install.

Sizing Your Tank:

The ideal size of your tank depends on factors like your water usage, roof size, and rainfall patterns.

A basic rule of thumb is to plan for around 1,000 liters of storage for every 100 square meters of roof area.

In areas with good rainfall (like parts of the North Island), you may only need a smaller tank. In drier areas, you may need a larger storage capacity.

Pros:

Easy to install, cost-effective.

Available in various materials to suit different needs.

Cons:

Large tanks can take up space, but underground or modular options can mitigate this.

Rainwater, while relatively clean, still needs to be filtered before it's safe for drinking or cooking. The level of filtration depends on your intended use.

Basic Filtration:

Pre-filtration: Install a coarse filter (like a mesh screen) on the downspout or before the tank to remove larger debris.

Activated Carbon Filters: Use these to improve taste and remove chlorine, odors, and other chemicals.

Sediment Filters: These remove smaller particles, such as sand, silt, and dirt, that may accumulate in the water.

Advanced Filtration for Drinking Water:

UV Purifiers: UV light can kill bacteria and viruses, making your water safe to drink.

Reverse Osmosis (RO): For highly purified water, an RO system can remove most contaminants, including heavy metals and salts.

Ceramic Filters: These are a good option for filtering out bacteria and larger particles.

For water distribution to your tiny home, you'll need a pump to get the water from the tank to the taps. Depending on your needs, you may also want a pressure system.

Options:

Shallow Well or Jet Pumps: Good for lifting water from ground-level or above-ground tanks.

Submersible Pumps: These sit at the bottom of the tank and push water to the surface.

Pressure Tanks: These ensure a consistent water flow to your taps and can help reduce pump cycling (turning on and off repeatedly).

Even with a good filtration system, maintaining water quality is essential.

Maintenance Tips:

Clean Your Tank Regularly: Once or twice a year, you should clean your water tank to remove sediment or algae that may build up.

Check Your Filters: Replace or clean filters as recommended by the manufacturer.

Inspect the Gutters and Downspouts: Clean them regularly, particularly in autumn when leaves fall.

In addition to collecting rainwater, consider setting up a greywater system to recycle water from sinks, showers, and laundry for use in irrigation or flushing toilets.

Options:

Greywater Diverters: Directs water from your shower or sink to your garden, reducing overall water consumption.

Greywater Filtration Systems: Clean the greywater before reusing it for things like irrigation or flushing.

Pros:

Reduces your water consumption.

Can be a great way to use water that’s already been filtered (i.e., not dirty or chemically laden).