(19)

(11)

EP 0 904 524 A1

(12)

(43) Date of publication: 31.03.1999 Bulletin 1999/13 (21) Application number: 97924134.0 (22) Date of filing: 30.05.1997

(51) International Patent Classification (IPC):  G01F 1/ 58( . ) G01F 1/ 60( . ) (86) International application number: PCT/GB1997/001468 (87) International publication number: WO 1997/046852 (11.12.1997 Gazette 1998/01)

(84) Designated Contracting States: AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE (30) Priority: 01.06.1996 GB 19960011498 (71) Applicant: SEVERN TRENT WATER LIMITED Birmingham, B26 3PU (GB)	(72) Inventor: SANDERSON, Michael Langley Cranfield, Bedford MK43 0JD (GB) (74) Representative: Makovski, Priscilla Mary, et al  BARKER BRETTELL 138 Hagley Road Edgbaston Birmingham B16 9PW Edgbaston Birmingham B16 9PW (GB)