Commitments and Contingencies

Operating Leases

The Company occupies certain facilities and operates certain equipment and vehicles under non‑cancelable lease arrangements. Lease agreements may contain lease escalation clauses and purchase and renewal options. The Company recognizes scheduled lease escalation clauses over the course of the applicable lease term on a straight-line basis in the Consolidated Statement of Operations.

Total rent expense was $20,088, $18,864 and $15,267 for the years ended September 30, 2019, 2018 and 2017, respectively.

Future minimum aggregate rental payments under non-cancelable operating leases are as follows:



Year Ended September 30,
2020	$	15,994
2021	12,714
2022	8,554
2023	6,147
2024	4,073
Thereafter	8,765
Total	$	56,247

Capital Leases

The Company leases certain equipment under leases classified as capital leases. The leased equipment is depreciated on a straight line basis over the life of the lease and is included in depreciation expense on the Consolidated Statements of Operations.

The gross and net carrying values of the equipment under capital leases as of September 30, 2019 and 2018 was as follows:



	September 30, 2019		September 30, 2018
Gross carrying amount	$	69,760	$	52,314
Net carrying amount	36,337		31,116

The following is a schedule showing the future minimum lease payments under capital leases by years and the present value of the minimum lease payments as of September 30, 2019.



Year Ended September 30,
2020	$	13,663
2021	10,328
2022	7,628
2023	5,033
2024	2,987
Thereafter	1,957
Total	41,596
Less amount representing interest (at rates ranging from 1.71% to 9.71%)	5,451
Present value of net minimum capital lease payments	36,145
Less current installments of obligations under capital leases	17,859
Obligations under capital leases, excluding current installments	$	18,286

The current installments of obligations under capital leases are included in Accrued expenses and other liabilities on the Consolidated Balance Sheets. Obligations under capital leases, excluding current installments, are included in other non-current liabilities on the Consolidated Balance Sheets.

The Company is a lessor to multiple parties. The Company purchases equipment through internal funding or bank debt equal to the fair market value of the equipment. The equipment is then leased to customers for periods ranging from five to twenty years. As of September 30, 2019, future minimum lease payments receivable under operating leases are as follows:



Year Ended September 30,
2020	$	5,986
2021	5,044
2022	5,072
2023	4,090
2024	3,967
Thereafter	55,737
Future minimum lease payments	$	79,896

Guarantees

From time to time, the Company is required to provide letters of credit, bank guarantees, or surety bonds in support of its commitments and as part of the terms and conditions on water treatment projects. In addition, the Company is required to provide letters of credit or surety bonds to the department of environmental protection or equivalent in some states in order to maintain its licenses to handle toxic substances at certain of its water treatment facilities.

These financial instruments typically expire after all Company commitments have been met, a period typically ranging from twelve months to ten years, or more in some circumstances. The letters of credit, bank guarantees, or surety bonds are arranged through major banks or insurance companies. In the case of surety bonds, the Company generally indemnifies the issuer for all costs incurred if a claim is made against the bond.

As of September 30, 2019 and 2018 the Company had Revolving Credit capacity to issue of $45,000 with letters of credit outstanding of $12,956 and $11,777, respectively, and remaining available of $32,044 and $33,223, respectively, under the Company's credit arrangements. As of September 30, 2019 and 2018 the Company had Surety capacity from surety underwriters of $220,000 and $200,000 with surety issuance of $144,717 and $123,427 and remaining available of $75,283 and $76,573. Additionally, as of September 30, 2018, the Company had letters of credit and surety bonds totaling $857 and $2,469, respectively, outstanding under the Company's prior arrangement with Siemens. No such amounts were outstanding as of September 30, 2019. The longest maturity date of letters of credit and surety bonds in effect as of September 30, 2019 was March 26, 2029.

Litigation

From time to time, as a normal incident of the nature and kind of business in which the Company is engaged, various claims or charges are asserted and litigation commenced against it arising from or related to: product liability; personal injury; trademarks, trade secrets or other intellectual property; labor and employee disputes; commercial or contractual disputes; breach of warranty; or environmental matters. Claimed amounts may be substantial but may not bear any reasonable relationship to the merits of the claim or the extent of any real risk of court or arbitral awards. While it is not feasible to predict the outcome of these matters with certainty, and some lawsuits, claims or proceedings may be disposed or decided unfavorably, the Company does not expect that any asserted or un-asserted legal claims or proceedings, individually or in the aggregate, will have a material adverse effect on the results of operations, or financial conditi