Emergency water tanks

After the Canterbury and Kaikoura earthquakes, many people bolstered their emergency preparedness by purchasing an emergency water tank that collects rainwater off the roof of a house or garage.

For example, 20,000 of these types of tanks have been sold in the Wellington region. The 200L tanks are manufactured by The Tank Guy, which also sells them direct to the public. In Wellington, and several other regions, water tanks are sold through local councils.

Here are our tips for maintaining a water tank and what to check before buying one.

Check regularly

It’s important you regularly check the tank’s in working order. To ensure it’s running well:

• Use some of the water on the garden – this refreshes the water supply and keeps the taps in working order.

• Check the tank every three months – empty it, give it a clean and then rinse it out with diluted unperfumed household bleach, then connect it back to the downpipe.

• Check the tap – if it’s not working, use a screwdriver to give the washer a gentle jiggle.

• Clean your gutters and remove any debris.

• Clear the diverter cup of any blockages.

Installation tips

If you’re going to install an emergency rainwater tank, you’ll need to connect the tank to your downpipe (which means you’ll have to cut the downpipe).

However, before you get the hacksaw out, check:

• which materials make up your roof – some materials contaminate collected water, while others will need to be treated

• where the tank will sit – it needs a flat, compacted base next to the downpipe that doesn’t block any access ways, and it’s essential the diverter (the bit of plastic that connects the downpipe to the tank) is level to prevent overflow

• there’s a big enough gap between your house and the downpipe – there needs to be space for the diverter to get around the downpipe to attach it (if the gap between your house and the pipe is too narrow, the diverter won’t fit and you’ll need a replacement)

• the size of your downpipe – in some older houses, the downpipe will be too small for a 65-80mm diverter to click snuggly on, and you’ll need to buy a smaller one

• there’s space for you to apply the strap that goes around the tank to keep it stable – the strap needs to be screwed on to the side of your house or a sturdy fence.

It’s a job a confident DIYer could tackle, but if that’s not you most plumbers should be up to the task. A straightforward installation should take about 45 minutes to an hour.

If you’re renting, check with your landlord before buying or installing.

Stand-alone storage

If you don’t have flat ground by a downpipe, your tank can be used as stand-alone water storage.

Brace the tank to a sturdy fence or the side of the house and fill it with water using the garden hose.

You’ll need to take these steps to ensure the water is safe to drink:

• Block the hole drilled for the diverter with tape on the inside and outside of the tank.

• Seal the rim of the tank with plastic food wrap so insects and dust won’t get in.

• Refresh the water every 12 months.

• Keep the parts that came with the tank in your emergency kit so, if there’s a natural disaster, you can use it to collect rainwater off the roof.

We’ve had reports of snails getting into water tanks. Make sure there are no gaps where they can get in and maintain your tank regularly. Snails release pathogens that will make you sick if you don’t boil or bleach the water before drinking.

Other water storage options

If your water supply gets cut, you’ll need at least 9L of water per person per day.

If you’re not keen on a tank, clean empty drink bottles, fill them with water and store them in a cool, dark place.

Don’t use empty milk bottles as they’ll have residual bacteria that will contaminate the water. You can also buy larger plastic containers (ranging from 8L to 20L).

If you’re storing water from a mains supply treated with chlorine you won’t need to add anything to it to make it safe to drink. Refresh the water every 12 months.

Boil or bleach?

Even if your emergency water tank is running perfectly, you’ll need to treat the water. Your options are either boiling or bleaching. Given the power could be out in the event of a natural disaster, you might have to rely on some type of outdoor cooker.

Even if you have that base covered, store some unperfumed bleach in your emergency kit just in case. For drinking, cooking and brushing your teeth, add a ½ teaspoon of bleach to 10L of water (or five drops per litre of water). For cleaning dishes or hard surfaces, add one teaspoon to a litre, or a ¼ cup to 10L.