Operating Segments (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Concentration risk
Consolidated net sales	$ 141,508,000	$ 120,058,000	$ 413,749,000	$ 357,372,000
Water Purification and Filtration
Concentration risk
Consolidated net sales	44,975,000	38,281,000	129,699,000	118,750,000
Dialysis
Concentration risk
Consolidated net sales	6,970,000	7,349,000	21,770,000	22,269,000
Healthcare Disposables
Concentration risk
Consolidated net sales	24,754,000	25,506,000	79,288,000	76,471,000
Segment sales | Customer concentration | Water Purification and Filtration
Concentration risk
Number of customers concentration risk			2
Segment sales | Customer concentration | Water Purification and Filtration | Two customers
Concentration risk
Concentration risk (as a percent)			46.30%
Segment sales | Customer concentration | Healthcare Disposables | Four customers
Concentration risk
Concentration risk (as a percent)			48.90%
Number of customers concentration risk			4
Net sales | Customer concentration | Da Vita Inc
Concentration risk
Concentration risk (as a percent)			10.50%
Consolidated net sales			$ 37,575,000
Net sales | Customer concentration | Dialysis | Da Vita Inc
Concentration risk
Concentration risk (as a percent)			29.20%