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Water filters (drinking) - what to ask before you buy

If you're thinking of buying a drinking water filter for your kitchen or bathroom taps, but you're not sure what to ask before you buy, here are some suggestions to help you decide which drinking water filter will best suit you.

Click on a question below for more information.

1. Need: Do I need a drinking water filter?
2. What does it do: What does the drinking water filter do?
3. Effectiveness: Will the drinking water filter remove all contaminants?
4. Water quality: How do I determine the local water quality?
5. Cost: How much does a drinking water filter cost?
6. Usage: How much will the drinking water filter have to process?
7. Filter cartridges: What kind of filter cartridges does the drinking water filter use?
8. Filter units: What types of drinking water filter units are available?
9. Process: What process does the drinking water filter use?
10. Testing: How can I be sure the drinking water filter really works?
11. Rainwater: Will the drinking water filter work with a rainwater tank?
12. Recycling: Can I recycle the drinking water filter cartridge?
13. Bottled water: Is bottled water an alternative?
14. Bathroom: Can I use the drinking water filter on the tap over the bathroom sink?

1. Do I need a drinking water filter?

If your household tap water tastes or smells bad, or you have reason to suspect it may be a health risk, first:

• Check to see if a regular mains flushing program is current - these are usually advertised in the local paper and on the radio.
• Run a tap close to the mains (i.e. near to your water meter) for a couple of minutes to see if the water runs clean.
• If it's still bad, it may be worth contacting your local water authority to make sure it's not a health problem associated with the local water supply. It may already be monitoring your water quality. If it's not a health concern, and you want to order a specific test, you're likely to incur a fee.

Occasional water discolouration can be caused by increased water flowing through water pipes - this is not usually a health risk and is caused by minute particles of iron and manganese.

• If you've run a load of washing and the water discolouration from the water supply has stained your clothes, contact the local water authority - some of these will provide you with a chemical to remove stains from the clothes.

If the water supply is okay, but you still don't like the taste or smell, or you want to improve the quality of your drinking water, then a drinking water filter may help.

Water is essential to life. Our brain and muscles are 75% water, our blood is over 80% water, and it's generally recommended that we drink 8 glasses of water a day. To improve the quality of the water you drink, a drinking water filter is a good choice.

2. What does the drinking water filter do?

Ask what the filter actually filters. Depending on the type (and cost) of the water filter, it will usually improve the taste of your drinking water, and will also filter out some of the following:

• Chemicals (e.g. agricultural chemicals, pharmaceuticals, petroleum products) which can enter the water supply through groundwater or as by-products of manufacturing processes.
• Microbes - bacteria, viruses, algae and parasites (e.g. cryptosporidium, giardia etc.)
• Metals (e.g. lead, cadmium, mercury, aluminium etc.)
• Fluoride, chlorine and ammonia (which may have been added by the water authority)
• Minerals which may damage household appliances if the water is 'hard'
• Other sediment which accumulates as the water flows through the system (e.g. rust particles, sand, soil etc.)

Determine, before you buy, what are the likely issues in your local water supply. That will help you decide what kind of drinking water filter will best suit you..

3. Will the drinking water filter remove all contaminants?

No. In some cases, for example if there is a breakdown at the water treatment plant, it may still be necessary for you to boil the water to remove dangerous contaminants.

4. How do I determine the local water quality?

Ask your local water supply authority - they will be able to provide you with information about water quality in your local area. The water supply authority may already test the water for the following water quality indicators:

• algae and bacteria
• taste and odour
• suspended solids
• acidity/alkalinity
• how much oxygen is dissolved in the water
• chemicals including metals, salts and by-products of water treatment such as fluoride and chlorine
• radioactivity in some areas

5. How much does a drinking water filter cost?

When you're finding out how much the water filter costs, ask about both:

• the initial cost of the unit and
• the cost of replacement filters, say for a year. This will give a better comparison than initial cost alone.

6. How much will the drinking water filter have to process?

Do a rough calculation of how much water you use, then you can figure out how long a filter cartridge will last... this will affect the running cost of the filter, and may determine the kind of filter you buy - for example, a jug type filter or a larger tap filter.

Once your filter has reached its capacity, it is important to replace it promptly as it may actually reduce the quality of your water once it gets clogged with sediment, microorganisms and other contaminants. Always keep a spare filter cartridge available because you're sure to want a new filter when the shops are closed!

7. What kind of filter cartridges does the drinking water filter use?

If you buy a bench top drinking water filter, ask if it takes a standard filter replacement cartridge - this are likely to be priced better than those unique to a particular water filter unit. The standard filter cartridges are available in many different types, depending on what you want to filter out of the water.

Other types of drinking water filter may require special filter cartridges. If you go with a big brand, it's more likely that replacement filters will be easy to obtain.

8. What types of drinking water filters are available?

• Jug type water filters- fairly cheap initial cost but may have higher ongoing filter replacement costs; may clog faster than tap filters due to the lower pressure pushing the water through the filter; no plumbing required.
• On tap water filters - fairly cheap initial cost; very convenient; easy filter replacement; can select filtered and unfiltered water; may require a converter to fit the specific tap; tap water pressure means they're less likely to clog than jug filters; no plumbing required.
• Bench top water filters - range from fairly cheap to expensive initial cost; tap water pressure means they're less likely to clog; large size means they work for longer before requiring replacement, but they do take up bench space in the kitchen; no plumbing required.
• Under sink water filters - the most expensive type; unlikely to clog; won't clutter the bench top but will take up under sink cupboard space; requires installation by a plumber.
• There is also a whole house water filter but it is beyond the scope of this article.

9. What process does the drinking water filter use?

• Carbon filters - trap the contaminants as they pass through the filter..
• Reverse osmosis - is very effective, uses high pressure to push the water through a membrane, which traps the contaminants and washes them away. However, it uses a lot of energy and wastes a lot of water.
• Water softeners - this type of filter will reduce the minerals in the water, thus reducing the lime scale buildup in your kettle.

Other processes are used to filter water but are not typically used in domestic drinking water filters - e.g. ultraviolet light treatment, alkalizing, and distillation.

10. How can I be sure the drinking water filter really works?

Look for a label indicating the water filter complies with the relevant standards. For example:

• NSF/ANSI Standard 42: Drinking Water Treatment Units - Aesthetic Effects
• NSF/ANSI Standard 53: Drinking Water Treatment Units - Health Effects

11. Will the drinking water filter work with a rainwater tank?

You must regularly monitor the quality of water from your rainwater tank.

Contaminants that may enter your tank include leaves and insects, bird droppings, degraded roof coatings, and agricultural chemicals (especially if you are near areas of aerial spraying). Identify what contaminants may affect your tank and obtain a water filter to suit.

Your local water supply authority can provide you with information about maintaining a tank water supply.

12. Can I recycle the water filter cartridge?

Ask if it is possible to recycle the water filter cartridge. Otherwise it will end up as landfill.

13. Is bottled water an alternative?

While bottled water is convenient for when you need water outside the home, a home drinking water filter will generally prove cheaper for day to day water consumption in the long run. Multiply the cost of a bottle of water by the recommended 8 glasses a day...

Furthermore, plastics used for bottled water may contain phthalates which can cause health problems once the plastic begins to degrade. While it is handy to refill these bottles with home-filtered water, replace them regularly and don't leave them in the sun or in a hot car, which may accelerate the degradation of the plastic.

14. Can I use the drinking water filter on the bathroom tap?

Some of the smaller 'on tap' filters can be fitted to a bathroom tap with the use of a thread converter which can be purchased from plumbing stores. Typically the thread on a bathroom tap does not match the one in the kitchen.

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