Business and segment information Segment reporting (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2014 Segments	Jan. 31, 2013 Segments	Jan. 31, 2012
Segment information [Line Items]
Entity Incorporation, Date of Incorporation		Oct. 12, 1993
Number of reportable segments	2	3
Net sales		$ 212,018	$ 233,496
Gross profit		38,107	36,321
Loss from operations		(7,265)	(5,063)
Loss before income taxes		(7,695)	(4,942)
Total assets		149,479	157,283
Capital expenditures		5,360	10,086
Depreciation expense		5,806	5,582
Impairment on fixed assets		1,520	0
Piping Systems [Member]
Segment information [Line Items]
Net sales		89,664	96,977
Gross profit		17,020	14,410
Loss from operations		3,452	1,143
Loss before income taxes		4,838	2,701
Total assets		83,944	74,953
Capital expenditures		4,206	8,396
Depreciation expense		3,344	3,076
Filtration Products [Member]
Segment information [Line Items]
Net sales		79,143	93,705
Gross profit		10,474	12,466
Loss from operations		(2,962)	614
Loss before income taxes			614
Total assets		52,958	55,095
Capital expenditures		995	1,449
Depreciation expense		1,750	1,734
Impairment on fixed assets		1,520	0
Industrial Process Cooling [Member]
Segment information [Line Items]
Net sales		37,131	32,112
Gross profit		10,240	8,541
Loss from operations		1,954	810
Loss before income taxes			810
Total assets		11,451	10,810
Capital expenditures		74	51
Depreciation expense		120	154
Corporate and Other [Member]
Segment information [Line Items]
Net sales		6,080	10,702
Gross profit		373	904
Loss from operations		(9,709)	(7,630)
Loss before income taxes		(11,525)	(9,067)
Total assets		1,126	16,425
Capital expenditures		85	190
Depreciation expense		$ 592	$ 618