It starts by requesting a free water testing strip from Brita. They also have detailed instructions which are very easy to follow and will show you how to test your water for hardness.
Click over to the next page to apply for yours, sent directly to your door.
Plus, if you sign up to the Brita mailing list while you're there, you will also get a £5 online shop voucher, special product information and tips and be the first to hear of exclusive promotional offers.