You may benefit from having an external use or sub meter if you use a large amount of water externally, for example:

• A very large garden that you water by hosepipe or sprinkler for more than 15 minutes each day
• A garden pond larger than 1 cubic metre or 220 gallons in capacity that you regularly fill or top up
• A swimming pool that you regularly fill or top up, that doesn’t drain into the main sewers
• An automatic garden irrigation system which is used daily for more than 15 minutes

The cost is £154.00 plus VAT and private plumber charges if required, therefore it may take some time before you’d see the benefits of the saving.

You may want to consider other options like a water butt or rain saver.