Sales grew 20% year-over-year, driven by 21% residential sales growth and 11% non-residential sales growth as we continued to execute at both ADS and Infiltrator in a favorable demand environment.
Both ADS and Infiltrator residential market sales grew over 20% in the fourth quarter, driven by favorable dynamics in new home construction, repair/remodel and on-site septic, accelerated by our material conversion strategies at both businesses.
Residential market sales have increased to 39% of our domestic sales as compared to 23% prior to the Infiltrator acquisition.
ADS participates in the repair/remodel segment of the residential market through retail, which is about 40% of the legacy business' residential sales.
About two-thirds of our domestic allied product sales are in the non-residential markets, where sales increased 13% further, giving us confidence in the underlying market strength.
Sales in the agriculture market increased 50% this quarter, driven by strong demand as the spring selling season got off to a good start.
International sales also increased 49%, primarily driven by sales growth in our Canadian business which nearly doubled compared to last year.
Finally, Infiltrator continues to exceed expectations with 23% sales growth in the fourth quarter against a very tough comparison to the prior year and broad-based growth across the Infiltrator product portfolio.
Adjusted EBITDA margin increased 190 basis points.
The ADS legacy business grew sales at 7.7% CAGR, driven by the sales programs we laid out in November 2018.
And the plan laid out in November 2018 restated our intention to grow adjusted EBITDA margin to between 18% and 19%.
The legacy ADS business finished fiscal 2021 with a margin of 24.3%, significantly outperforming our plan.
The improvement in profitability as well as execution of our working capital initiatives and the acquisition of Infiltrator drove the improvement in free cash flow conversion to 66% of adjusted EBITDA, significantly better than the 45% in fiscal 2018 and above our target of at least 50%.
And since the acquisition of Infiltrator, we are more exposed to the residential construction market, which now represents nearly 40% of sales.
Our strong topline revenue growth of 20% was driven by both volume and pricing, with strong growth across our ADS and Infiltrator businesses as well as in each of our segments, markets and product applications.
The 31% growth in consolidated adjusted EBITDA was driven by strong topline growth in addition to favorable pricing, operational efficiency initiatives, as well as our synergy programs.
In addition, due to the strong results for fiscal 2021 and to reward the incredible service and dedication of our employees this past year, we decided to pay a one-time bonus to employees who were not part of our annual incentive compensation plans, resulting in approximately $4 million of additional compensation expense in the quarter.
Revenue this year increased 19% to $1.983 billion, coming in above the high end of our guidance range.
Our adjusted EBITDA increased $205 million to $567 million, driven by strong volume growth in both pipe and allied products, favorable pricing and material costs, and operational efficiency initiatives that offset inflationary cost pressures.
Infiltrator contributed an additional $88 million, driven by strong volume growth, favorable price/cost performance as well as continued benefits from our synergy programs.
Finally, our adjusted EBITDA margin increased 700 basis points to 28.6%, a Company record.
Our year-to-date free cash flow increased $134 million to $373 million as compared to $239 million in the prior year.
Our working capital decreased to approximately 18% of sales, down from 21% of sales last year.
Further, our trailing 12-month leverage ratio is now 1.1 times.
We ended the quarter in a favorable -- very favorable liquidity position with $195 million of cash and $339 million available under our revolving credit facility, bringing our total liquidity to $534 million.
Based on our performance to date, order activity, backlog and current market trends, we currently expect net sales to be in the range of $2.220 billion to $2.300 billion, representing growth of 12% to 16% over this past year, and adjusted EBITDA to be in the range of $635 million to $665 million, representing growth of 12% to 17% over this past year.
In fiscal 2022, we plan to spend between $130 million and $150 million on capital expenditures to support growth, recycling, innovation, productivity, and safety initiatives at both ADS and Infiltrator, basically doubling our commitment to capex year-over-year.
In addition to investing in the business through deploying capital organically and through M&A, we, today, announced a 22% increase in our quarterly dividend as well as a $250 million increase in our share repurchase program.
We previously had $42 million available under this program, and the increase announced today brings the total authorization to $292 million.

Summary:
Based on our performance to date, order activity, backlog and current market trends, we currently expect net sales to be in the range of $2.220 billion to $2.300 billion, representing growth of 12% to 16% over this past year, and adjusted EBITDA to be in the range of $635 million to $665 million, representing growth of 12% to 17% over this past year.