Ken Tesh's stuff is pretty formulaic and good, plenty of content! https://www.amazon.com/Practice-Exams-Distribution-Operator-Certification/dp/1985652390/ref=sr_1_1?crid=2QURYR7HC101&keywords=Water+Distribution+Practice+Exams&qid=1660224091&sprefix=water+distribution+practice+exams%2Caps%2C129&sr...
I used this workbook and looked up each question I missed or guessed on. The math in this is harder than the exam so if you can master it then the exam is easy.
If you passed the treatment exam, you’ll pass the distribution one. I found the D2 was really easy in comparison to the T2 exam
Practice Exams - Water Distribution Operator Certification: Grades 1 and 2 https://smile.amazon.com/dp/1985652390/ref=cm_sw_r_cp_api_glt_fabc_C8SX2MD3270QTXDS5T7M
That book helped me a lot
Im studying for the D2 test and I’ve been using flash cards to help
https://quizlet.com/213710234/water-distribution-finale-study-guide-flash-cards/ Whatever I got wrong from here I would write them down on flash cards.
Also bought this practice exam book off amazon and made more flash cards based off the answers I got wrong. https://www.amazon.com/Practice-Exams-Distribution-Operator-Certification/dp/1985652390
I used this to pass my 2’s most of the stuff there I encountered on my exam. I’m also from CA too.
Practice Exams - Water Distribution Operator Certification: Grades 1 and 2 https://www.amazon.com/dp/1985652390/ref=cm_sw_r_cp_apip_isN8siHY1kYvv
That book will help before you take the exam