While 18-litre flushes (4 UK gal, 4.75 US gal) are still not uncommon in Canada, adequate flushing is possible with substantially lower volumes of water.

What to look for

• Low water use

  We recommend 6 litres per flush or lower. (That's 1.6 US gallons, or 1.3 UK gallons.) Our latest research indicates that all Caroma, Toto and Niagara Flapperless units meet this criterion, as do most (but not all) by American Standard Canada, Crane Plumbing and Kohler. Most new units in the shops now meet our criteria - but look out for the ones that don't! (And consider buying one that does even better.)

• Reduce water use still further

  Dual flush toilets can operate at 2 flush volumes (typically 3 litres and 6 litres), depending on what it is you're flushing…

• Adequate flushing

  Low water use should never be an excuse for inadequate flushing performance. Toilets should meet the requirements of the relevant Canadian standard (CSA-B45: available at some large public libraries).

• or, if you don't want to buy a new unit,

  Proprietary retrofit systems which permit reduction of flushing volume. These include water bags for insertion in the toilet tank to displace usable water, "dams" to prevent movement of some of the cistern water, quick-return flapper valves and other adaptations to the flushing mechanism. However, these come with a "health warning"--depending on the nature of the toilet being adapted, adequate evacuation may or may not be possible. (Some toilet bowls are just the wrong shape for efficient use of water - the only sure way to find out whether yours is one of these is trial and error. Fortunately all of these options are inexpensive, so if it doesn't work it isn't a financial disaster.)