HC Deb 05 February 1953 vol 510 cc239-40W
96. Mr. R. Bell

asked the Minister of Housing and Local Government what proportion of chalk, either by weight or by volume, is present in London drinking water.

Mr. Marples

By chalk my hon. and learned Friend presumably means calcium bicarbonate, the form in which calcium carbonate is held in solution in water. The concentration in London drinking water varies with the source of the water, and to a certain extent with the time of the year, but generally it ranges between 160 and 250 parts per million by weight expressed as calcium carbonate.