Build a rainwater system

Harvesting precious rainwater so you can feed your vegetable garden is easy if you follow these simple steps. We chose to upcycle a beautiful old oak wine barrel, but there are lots of different vessels you could use. It is important to remember that this system is only for watering the garden, not for drinking.

You’ll need...

• Barrel and rainwater harvesting kit – $315 from Barry’s Barrels www.bb.net.nz (or if you already have your barrel, a downpipe tap diverter costs $65)
• Length of standard garden hose to fit (if you don’t already have one that you are willing to cut) – between 50 cents and $1 per metre from a hardware store
• Light-duty fasteners – for concrete, use 5mm x 20mm round head nylon anchors (approx. 15 cents each); if fastening to wood, use small stainless steel screws
• Chicken wire 13mm ‘hex’, 900mm x 1m – $4.80
• Small piece of sandpaper, between P60 – P120 grit (though used sandpaper or even a file will work fine) – $3.50 per sheet of P80
• Plumbing coupling (this is only needed for difficult sites where the downpipe is short) – $14.28 from Mico Plumbing www.mico.co.nz

Tools required...

• Tape measure
• Level
• Hacksaw
• Drill (cordless drill for wood screws or an impact drill with hammer function for concrete as pictured)
• Appropriate drill bits (again depending on your type of wall and nails/screws)
• Hammer (if you are putting nylon anchors into a concrete wall)
• Screwdriver (if you are using the coupling for a difficult site)

Step 1: Plan your site

Before getting into the job, you need to check where your downpipe (the pipe that comes down from the gutter) is situated in relation to the garden you are watering and the size of the barrel. 

You will need the tank on level and solid ground. It will be very heavy when full.

It is also important that the bottom of the tank sits higher than your garden so that the hose has a reasonable flow of water. If this is impossible, you can purchase a solar powered pump or just fill up watering cans.

A standard wine barrel is 900mm high. You may want to raise the barrel on cinder blocks first so you can fit a bucket or watering can underneath the tap. Make sure that the top of your tank sits at least 400mm below the section of downpipe that you are going to cut and not near any joins.

Step 2: Filtering the gutter

Protect the system from blockage by using a gutter witch. Our supplier Barry’s Barrels include a standard one in their kitset, but if you have an internal gutter as we did (they’re usually on commercial buildings only) it may be too wide for the witch. A cheap and easy alternative is rolled up chicken wire.

Step 3: Position the downpipe converter

Measure where you want to put the downpipe converter. This is the crucial piece that separates water until your tank is full, at which point it will overflow back into your downpipe.

With limited space on our site, we decided to use a black coupling, which gives you more flexibility. At most houses this won’t be necessary, as the converter will tap straight into your downpipe.

Place the downpipe converter against your downpipe and mark your cut, being sure to leave 50mm of spare pipe top and bottom so the converter and the downpipe fit together.

Step 4: Install the downpipe converter

Cut the downpipe: Use a hacksaw to cut out a section of downpipe (use sandpaper on the edges until smooth, being careful to get the plastic pieces into the rubbish rather than the drain!).

Placing the downpipe converter: Remove any brackets that are attaching the downpipe to the wall. Do this carefully so you don’t break the plastic. If you are delicate enough you can often re-use the nails/screws.

If you are using a black coupling like we did, put this over the upper section of downpipe now (tighten it temporarily with a screwdriver so it stays out of the way).

Next, insert one shoe from the converter on to the downpipe that comes from the gutter all the way to the hilt. Gently bend the pipe away from the house to slide the other shoe on to the downpipe.

If you are using a coupling, fasten this on with a screwdriver now.

Step 5: Replace the fastener  

If your wall is wood, you can probably replace the screws that you removed in the previous step. If it is concrete, mark a new spot for the brackets and carefully drill guide holes. If you are drilling concrete, you need a masonry bit. Always wear eye protection when drilling concrete.

Next, fasten the bracket on with the appropriate screws/nails. These don’t need to be heavy-duty, as they are not holding any weight.

Step 6: Install the hose

Cut a piece of your standard garden hose, making sure that the bends going to the tank are not too sharp (otherwise it will kink) and connect to the tank. Now you can plug in a standard garden hose to the tap at the bottom of the tank. You’re done! All you need now is some rain...

Our suppliers: Barry's Barrels provided the lovely wine barrel and rainwater harvesting kit. www.bb.net.nz, phone 0508 BARREL. Auckland Landscaping Supplies provided materials to prepare and finish off the project area. www.aucklandlandscape.co.nz, phone 09 521 3412.