For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13537-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

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-Section 50

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Section 50

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- Definition

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

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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.

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- Definition

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

+ References

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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=26872669&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

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Business segment reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended									12 Months Ended	3 Months Ended
	Apr. 30, 2014 Segments	Apr. 30, 2013	Apr. 30, 2014 Piping Systems [Member]	Apr. 30, 2013 Piping Systems [Member]	Apr. 30, 2014 Filtration Products [Member]	Apr. 30, 2013 Filtration Products [Member]	Apr. 30, 2014 Corporate Segment [Member]	Apr. 30, 2013 Corporate Segment [Member]	Apr. 30, 2014 Credit Concentration Risk [Member]	Jan. 31, 2014 Credit Concentration Risk [Member]	Apr. 30, 2014 Sales Revenue, Net [Member]
Segment reporting
Number of reportable segments	2
Net sales	$ 59,524	$ 54,691	$ 42,354	$ 36,058	$ 17,170	$ 18,633
Gross profit	15,989	12,719	13,458	10,444	2,531	2,275
Income from operations	$ 5,709	$ 2,533	$ 8,017	$ 5,380	$ (544)	$ (483)	$ (1,764)	$ (2,364)
Concentration Risk, Percentage									42.00%	24.00%	21.00%