Select Energy Services (WTTR) 10-K 2020 FY Annual report

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We have issued our reports dated February 24, 2021, with respect to the consolidated financial statements and internal control over financial reporting included in the Annual Report of Select Energy Services, Inc. on Form 10-K for the year ended December 31, 2020. We consent to the incorporation by reference of said reports in the Registration Statements of Select Energy Services, Inc. on Forms S-8 (File No. 333-217561, File No. 333-221282, File No. 333-222816, and File No. 333-241656) and Form S-3 (File No. 333-224956).

/s/ Grant Thornton LLP

Dallas, Texas

February 24, 2021