Business segment reporting (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017 USD ($) Segments	Jul. 31, 2016 USD ($)	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)
Segment reporting
Number of reportable segments | Segments	1
Net sales	$ 26,852	$ 22,859	$ 50,353	$ 45,928
Gross profit	3,058	2,980	4,843	4,972
Loss from operations	(2,105)	(2,190)	$ (5,922)	(6,790)
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
Net sales	26,852	22,859	$ 50,353	45,928
Gross profit	3,058	2,980	4,843	4,972
Loss from operations	62	(714)	(1,397)	(2,415)
Corporate Segment [Member]
Segment reporting
Loss from operations	$ (2,167)	$ (1,476)	$ (4,525)	$ (4,375)