Business segment reporting (Details)	3 Months Ended
Apr. 30, 2018 Segments
Segment reporting
Number of reportable segments	1
Piping Systems [Member]
Segment reporting
Segment reporting information, description of Products and Services	Piping Systems engineers, designs, manufactures and sells specialty piping, leak detection and location systems

Description of the types of products and services from which the reportable segment derives its revenue.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8721-108599

Name:	us-gaap_DescriptionOfTypesOfProductsAndServicesFromWhichEachReportableSegmentDerivesItsRevenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration