Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Mar. 31, 2019	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Mar. 31, 2019	Apr. 01, 2018	Apr. 02, 2017
Summary of Segment Information
Sales		$ 133,051	$ 128,151	$ 145,324	$ 149,800	$ 126,990	$ 118,053	$ 125,395	$ 133,731	$ 556,326	$ 504,169	$ 483,593
Gross profit		20,674	21,033	25,772	28,457	17,806	18,840	24,115	25,999	95,936	86,760	98,073
Selling, general, and administrative expenses		14,886	14,312	14,941	14,979	14,670	14,139	14,828	15,766	59,118	59,403	59,381
Goodwill impairment						39,116	0	0	0	0	39,116	0
Operating income		5,788	$ 6,721	$ 10,831	$ 13,478	(35,980)	$ 4,701	$ 9,287	$ 10,233	36,818	(11,759)	38,692
Identifiable assets	[1]	367,242				376,688				367,242	376,688	404,524
Capital expenditures										12,618	19,703	21,616
Industrial [Member]
Summary of Segment Information
Sales										281,860	247,374	238,555
Gross profit										34,900	29,619	38,886
Selling, general, and administrative expenses										22,759	21,159	21,818
Goodwill impairment											0
Operating income										12,141	8,460	17,068
Identifiable assets	[1]	162,926				165,052				162,926	165,052	159,032
Capital expenditures										7,319	10,265	10,529
Water Treatment [Member]
Summary of Segment Information
Sales										149,490	138,465	128,954
Gross profit										37,986	36,268	35,962
Selling, general, and administrative expenses										19,498	19,426	19,798
Goodwill impairment											0
Operating income										18,488	16,842	16,164
Identifiable assets	[1]	58,274				58,513				58,274	58,513	53,445
Capital expenditures										4,506	7,228	7,777
Health and Nutrition [Member]
Summary of Segment Information
Sales										124,976	118,330	116,084
Gross profit										23,050	20,873	23,225
Selling, general, and administrative expenses										16,861	18,818	17,765
Goodwill impairment											39,116
Operating income										6,189	(37,061)	5,460
Identifiable assets	[1]	146,042				153,123				146,042	153,123	192,047
Capital expenditures										793	2,210	3,310
Unallocated Amount to Segment [Member]
Summary of Segment Information
Identifiable assets		$ 18,400				$ 14,300				$ 18,400	$ 14,300	$ 13,100

[1] Unallocated assets, consisting primarily of cash and cash equivalents, investments and prepaid expenses, were $18.4 million at March 31, 2019, $14.3 million at April 1, 2018 and $13.1 million at April 2, 2017.