EX-5.1

SJW Group

April 25, 2018

Page 2

We have also examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company and such agreements, certificates and receipts of public officials, certificates of officers or other representatives of the Company and others, and such other documents as we have deemed necessary or appropriate as a basis for the opinion stated below.

In our examination, we have assumed the genuineness of all signatures, including endorsements, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as facsimile, electronic, certified or photostatic copies, and the authenticity of the originals of such copies. In making our examination of executed documents, we have assumed that the parties thereto, other than the Company, had the power, corporate or other, to enter into and perform all obligations thereunder and have also assumed the due authorization by all requisite action, corporate or other, and the execution and delivery by such parties of such documents and the validity and binding effect thereof on such parties. As to any facts relevant to the opinion stated herein that we did not independently establish or verify, we have relied upon statements and representations of officers and other representatives of the Company and others and of public officials.

In rendering the opinion stated herein, we have also assumed that (i) if issued in physical form, the certificates evidencing the Registered Shares will be signed by the authorized officers of the Company and registered by the transfer agent and registrar and will conform to the specimen certificate examined by us evidencing the Common Stock or, if issued in book-entry form, an appropriate account statement evidencing the Registered Shares credited to the recipient’s account maintained with said transfer agent has been issued by said transfer agent and (ii) the issuance of the Registered Shares will be properly recorded in the books and records of the Company.

We do not express any opinion with respect to the laws of any jurisdiction other than the General Corporation Law of the State of Delaware, and we do not express any opinion as to the effect of any other laws on the opinion stated herein.

Based upon the foregoing and subject to the qualifications and assumptions stated herein, we are of the opinion that when the Registration Statement becomes effective under the Securities Act, the stockholders of the Company approve of the issuance of the Issued Shares and the adoption of SJW’s Certificate of Incorporation Amendment, the Merger is consummated in accordance with the terms of the Merger Agreement, the SJW Certificate of Incorporation Amendment has been filed with the Secretary of State of the State of Delaware and such SJW Certificate of Incorporation Amendment becomes effective, and the Issued Shares have been delivered in accordance with the terms of the Merger Agreement and pursuant to the Registration Statement, the Issued Shares will be validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. We also consent to the reference to our firm under the caption “Legal Matters” in the Registration Statement. In giving this consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder. This opinion is expressed as of the date hereof unless otherwise expressly stated and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable law.

Very truly yours,

/s/ Skadden, Arps, Slate, Meagher & Flom LLP

LBK