37 Installation and repair of irrigation devices; installation and maintenance of irrigation systems; installation, maintenance and repair of water supply apparatus; installation of water pipes; installation, repair, servicing, replacement and reconditioning of ducts; laying, servicing and repair of pipelines, hoses and high pressure ducts for hydraulic systems; laying, repair, servicing, replacement and reconditioning of ducts; maintenance of water purifying apparatus; maintenance of water pollution control equipment; installation of sanitary apparatus; repair of sanitary installations; providing information with respect to the repair or maintenance of water purifying apparatus; provision of information relating to the repair or maintenance of water pollution control equipment; repair of water supply apparatus; installation of environmental protection systems