Business and segment information Segment reporting (Details) $ in Thousands	12 Months Ended
	Jan. 31, 2017 USD ($) Segments	Jan. 31, 2016 USD ($)
Segment information [Line Items]
Entity Incorporation, Date of Incorporation	Oct. 12, 1993
Number of reportable segments | Segments	1
Net sales	$ 98,845	$ 122,696
Gross profit	11,716	26,741
Income (loss) from operations
Income (loss) from operations	(10,788)	2,878
Segment assets	101,611	138,098
Capital expenditures	2,257	5,051
Depreciation and amortization	5,336	4,200
Piping Systems [Member]
Segment information [Line Items]
Net sales	98,845	122,696
Gross profit	11,716	26,741
Income (loss) from operations
Income (loss) from operations	(2,435)	10,537
Segment assets	98,855	112,161
Capital expenditures	1,925	4,762
Depreciation and amortization	5,009	3,735
Corporate [Member]
Income (loss) from operations
Income (loss) from operations	(8,353)	(7,659)
Segment assets	2,731	10,229
Capital expenditures	332	289
Depreciation and amortization	327	469
Operating Segments [Member]
Income (loss) from operations
Segment assets	$ 101,586	$ 122,390