Alternative channels
Mail, text, and in-person payment instructions
Pay by text
Cal Water's PromisePay arrangement service at calwater.promise-pay.com can provide payment-plan reminders by text to residential customers with a past-due balance of at least $50, but the reviewed materials do not describe a general text-to-pay keyword or a standalone San Carlos text-payment enrollment flow. Customers should enroll through the official Cal Water assistance page or customer portal and confirm the sender before following a payment link. Regular bill payment is available through the portal or the automated phone number.
Mail-in address
California Water Service, P.O. Box 7229, San Francisco, CA 94120-7229. Include the Cal Water account number on the check or money order, use the payment stub when available, and do not send cash through the mail.
Counters, drop boxes, and office hours
The Bayshore district office serving San Carlos is at 341 North Delaware Street, San Mateo, CA 94401, with posted district hours Monday through Friday, 7:00 a.m. to 7:00 p.m.; Cal Water expressly states that in-person customer service is not available at that location. Customers can use the secure Cal Water office drop box where available, Walmart Bill Pay during the store's normal business hours, or a Western Union pay station. Walmart accepts cash or debit card for Cal Water Bill Pay, requires the full account number, uses WMBP same-day processing, and has a $1,500 transaction limit; Western Union availability and any fee should be confirmed at the location.