Business segment reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012 Segments	Jul. 31, 2011	Jan. 31, 2012
Segment reporting
Number of reportable segments			3
Net sales	$ 52,261	$ 63,990	$ 104,989	$ 117,391
Gross profit	9,906	10,784	19,034	19,026	36,321
Income (loss) from operations	(671)	88	(2,390)	(1,556)
Loss before income taxes	(1,022)	(160)	(3,358)	(2,274)	(4,942)
Piping Systems [Member]
Segment reporting
Net sales	22,905	26,339	42,649	45,366
Gross profit	4,869	4,631	8,267	7,444
Income (loss) from operations	1,443	927	1,598	704
Loss before income taxes	1,511	1,011	1,421	605
Filtration Products [Member]
Segment reporting
Net sales	19,276	25,279	42,252	50,122
Gross profit	2,552	3,537	5,664	6,849
Income (loss) from operations	(292)	516	(96)	1,026
Loss before income taxes	(292)	516	(96)	1,026
Industrial Process Cooling [Member]
Segment reporting
Net sales	8,895	8,231	18,026	15,386
Gross profit	2,437	2,226	4,969	4,171
Income (loss) from operations	314	293	877	497
Loss before income taxes	314	293	877	497
Corporate and Other [Member]
Segment reporting
Net sales	1,185	4,141	2,062	6,517
Gross profit	48	390	134	562
Income (loss) from operations	(2,136)	(1,648)	(4,769)	(3,783)
Loss before income taxes	$ (2,555)	$ (1,980)	$ (5,560)	$ (4,402)

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Article 5

+ Details

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

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- Details

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