Business segment reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Apr. 30, 2013 Segments	Apr. 30, 2012
Segment reporting
Number of reportable segments	2
Net sales	$ 57,744	$ 44,499
Gross profit	13,132	6,832
Income (loss) from operations	2,805	(2,297)
Income (loss) from continuing operations before income taxes	2,020	(2,914)
Piping Systems [Member]
Segment reporting
Net sales	36,058	19,744
Gross profit	10,444	3,398
Income (loss) from operations	5,380	155
Income (loss) from continuing operations before income taxes	5,084	(91)
Filtration Products [Member]
Segment reporting
Net sales	18,633	22,976
Gross profit	2,275	3,112
Income (loss) from operations	(483)	196
Income (loss) from continuing operations before income taxes	(483)	196
Corporate and Other [Member]
Segment reporting
Net sales	3,053	1,779
Gross profit	413	322
Income (loss) from operations	(2,092)	(2,648)
Income (loss) from continuing operations before income taxes	$ (2,581)	$ (3,019)

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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