Business segment reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014 Segments	Oct. 31, 2013	Oct. 31, 2014 Piping Systems [Member]	Oct. 31, 2013 Piping Systems [Member]	Oct. 31, 2014 Piping Systems [Member]	Oct. 31, 2013 Piping Systems [Member]	Oct. 31, 2014 Filtration Products [Member]	Oct. 31, 2013 Filtration Products [Member]	Oct. 31, 2014 Filtration Products [Member]	Oct. 31, 2013 Filtration Products [Member]	Oct. 31, 2014 Corporate Segment [Member]	Oct. 31, 2013 Corporate Segment [Member]	Oct. 31, 2014 Corporate Segment [Member]	Oct. 31, 2013 Corporate Segment [Member]	Oct. 31, 2014 Credit Concentration Risk [Member]	Jan. 31, 2014 Credit Concentration Risk [Member]	Oct. 31, 2013 Sales Revenue, Net [Member]
Segment reporting
Number of reportable segments			2
Segment Reporting Information, Description of Products and Services							Piping Systems which engineers, designs, manufactures and sells specialty piping, leak detection and location systems				Filtration Products, which manufactures custom-designed industrial filtration products to remove particulates from air and other gas streams
Concentration Risk, Percentage																	33.00%	24.00%	13.00%
Net sales	$ 43,819	$ 57,967	$ 156,713	$ 173,460	$ 26,540	$ 42,289	$ 102,683	$ 121,825	$ 17,279	$ 15,678	$ 54,030	$ 51,635
Gross profit	6,721	16,887	33,255	43,037	4,609	14,726	25,913	35,760	2,112	2,161	7,342	7,277
(Loss) income from operations	$ (1,236)	$ 6,787	$ 6,268	$ 14,093	$ 1,096	$ 9,403	$ 12,896	$ 21,276	$ (726)	$ (486)	$ (1,300)	$ (468)	$ (1,606)	$ (2,130)	$ (5,328)	$ (6,715)