Water Hardness
Hard water is water supplied to your home which contains Calcium Carbonate, potasium and Magnesium at quantities over 120ppm or parts per million. Water supplied in the Newbury, Oxford and Swindon areas is classified as hard or very hard. This water is generally at around 200 to 300ppm. For information on your water hardness and other water quality issues you can visit the Thames water website: https://www.thameswater.co.uk/help/water-quality/check-your-water-quality#/search
You will find a report for the water quality in your area and if you look down on the page there is a figure for total hardness CaCo3 in Mg/l in my case 300Mg per litre or 300 parts per million. 300 or above is ‘very hard’ and needs treating