Business segment reporting (Details) - Segments	3 Months Ended	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2018
Segment reporting
Number of reportable segments	1
Piping Systems [Member]
Segment reporting
Segment reporting information, description of Products and Services		Piping Systems engineers, designs, manufactures and sells specialty piping, leak detection and location systems