Segment Information (Details) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 01, 2016 USD ($)	Apr. 02, 2016 Segment	Sep. 26, 2015 USD ($)	Oct. 01, 2016 USD ($)	Sep. 26, 2015 USD ($)	Dec. 26, 2015 USD ($) Segment
Segment Information [Abstract]
Number of reportable segments | Segment		3				2
Summary of segment information [Abstract]
Net sales	$ 506,584		$ 535,184	$ 1,583,464	$ 1,628,019
Cost of goods sold	424,668		467,167	1,327,370	1,398,366
Depreciation and amortization	9,016		8,749	26,997	24,790
Selling, general, and administrative expense	32,413		32,241	102,707	97,922
Asset impairments	3,000		0	3,000	570
Gain on sale of assets	0		0	0	(15,376)
Severance	0		0	0	3,442
Operating income	37,487		27,027	123,390	118,305
Interest expense	(1,830)		(1,682)	(5,370)	(5,977)
Other income, net	120		164	880	534
Income before income taxes	35,777		25,509	118,900	112,862
Segment assets	1,426,121			1,426,121		$ 1,338,801
Piping Systems [Member]
Summary of segment information [Abstract]
Segment assets	855,036			855,036		811,343
Industrial Metals [Member]
Summary of segment information [Abstract]
Segment assets	160,413			160,413		153,102
Climate [Member]
Summary of segment information [Abstract]
Segment assets	61,713			61,713		61,672
General Corporate [Member]
Summary of segment information [Abstract]
Segment assets	348,959			348,959		$ 312,684
Operating Segments [Member] | Piping Systems [Member]
Summary of segment information [Abstract]
Net sales	351,557		367,892	1,109,109	1,109,124
Cost of goods sold	301,867		320,571	949,015	959,599
Depreciation and amortization	5,905		5,430	17,341	15,952
Selling, general, and administrative expense	16,647		16,469	51,497	50,021
Asset impairments	3,000			3,000	570
Gain on sale of assets					(15,376)
Severance					3,442
Operating income	24,138		25,422	88,256	94,916
Operating Segments [Member] | Industrial Metals [Member]
Summary of segment information [Abstract]
Net sales	131,350		139,472	393,608	435,736
Cost of goods sold	107,512		125,146	321,615	373,678
Depreciation and amortization	1,964		2,154	6,219	5,452
Selling, general, and administrative expense	3,125		3,044	9,989	8,044
Asset impairments	0			0	0
Gain on sale of assets					0
Severance					0
Operating income	18,749		9,128	55,785	48,562
Operating Segments [Member] | Climate [Member]
Summary of segment information [Abstract]
Net sales	30,003		28,494	92,068	85,803
Cost of goods sold	22,210		22,160	68,363	67,561
Depreciation and amortization	612		608	1,829	1,647
Selling, general, and administrative expense	2,357		2,283	7,336	6,637
Asset impairments	0			0	0
Gain on sale of assets					0
Severance					0
Operating income	4,824		3,443	14,540	9,958
Corporate and Eliminations [Member]
Summary of segment information [Abstract]
Net sales	(6,326)		(674)	(11,321)	(2,644)
Cost of goods sold	(6,921)		(710)	(11,623)	(2,472)
Depreciation and amortization	535		557	1,608	1,739
Selling, general, and administrative expense	10,284		10,445	33,885	33,220
Asset impairments	0			0	0
Gain on sale of assets					0
Severance					0
Operating income	$ (10,224)		$ (10,966)	$ (35,191)	$ (35,131)