About Efficient Water Heaters, Inc.
The Navien Specialist Behind This Site: Joseph J. Castro
Owner-led water heater specialty work serving San Jose and the South Bay since 1997 — one trade, done by the person who answers the phone.
- Navien Service Specialist
- Rinnai PRO
- Noritz Certified
- CSLB #1008381
Who runs Efficient Water Heaters?
Joseph J. Castro is the owner and CEO of Efficient Water Heaters, Inc., a San Jose-born, certified Navien Service Specialist who has worked the Bay Area water heater trade since 1997. His company installs, services, and maintains Navien tankless water heaters across 19 South Bay and Peninsula cities, licensed under CSLB #1008381 and bonded and insured. Reach him directly at (408) 470-0191, open 24 hours a day, 7 days a week.
One trade, on purpose
Joseph was born in San Jose, and he built the company around a single promise: water heaters are the whole job, not one line item on a general plumbing menu. Since 1997 that has meant showing up for Bay Area homeowners and property managers with the parts, the training, and the answers for one category of equipment.
The narrow focus pays off in ordinary ways. Diagnosis moves faster because the failure patterns are familiar. Estimates can be quoted from photos, before anyone drives out. Installs come out cleaner because the venting, gas sizing, and mounting have been done hundreds of times. And when a repair is the smarter call, you hear that instead of a replacement pitch.
That experience spans the range of buildings the South Bay actually has: older San Jose houses with cramped utility closets, modern garages, ADUs behind the main house, multifamily buildings, restaurants, and commercial spaces where hot water outages stop the day.
Credentials you can check before we touch a gas line
Navien Service Specialist
Factory training on Navien diagnostics means the fault is traced to the actual part — igniter, flame rod, flow sensor, or scaled heat exchanger — instead of guessed at. Correct Navien parts and documented procedures also keep the manufacturer warranty intact.
Rinnai PRO
Rinnai training covers a second major tankless platform, so a Rinnai unit in the garage gets the same informed diagnosis rather than a shrug and a replacement quote.
Noritz Certified
Noritz certification rounds out the third of the big tankless brands installed across South Bay homes and small commercial buildings.
CSLB #1008381 · Bonded & Insured
The license is active, bonded, and insured, and you can confirm it yourself on the state contractor board's lookup before anyone touches a gas line.
Verify our license →Holding all three major tankless manufacturer credentials means the advice is brand-agnostic — we recommend what fits your home, not what we are limited to.
How we work
Photos first, phone estimate second
Send pictures of the unit, its data plate, and the connections, and most jobs can be scoped over the phone before anyone drives out.
The owner stays on the job
Joseph handles estimates, works installs, and answers the messages in between — the person quoting the job is the person accountable for it.
Permit-ready, code-correct work
Seismic strapping, venting runs, gas line sizing, and expansion tanks are sized and installed to pass inspection, not to pass a glance.
No high-pressure upsells
If a flush and a flame rod cleaning buys another five years, that is the recommendation you get. Replacement is proposed when the math supports it.
What customers said, in their words
“I asked a lot of questions about tankless. Joseph was quick in responding and the answers were unbiased and helpful. Marco helped us install the water heater. He is efficient, professional, and the job was very well done. Price is fair — I got the best quote comparing with 2 other vendors who have good reviews on Yelp. Highly recommend.”
“We were in a bind. Had no water and couldn't get ahold of anyone on the weekend. Joseph responded immediately. Scheduled an appointment the next day and gave us a beautiful new tankless hot water heater for the same price as the previous person quoted for a 40-gallon. His work was very nicely done and we are very happy with our new efficient water heater.”
“Had a great experience with the guys at Efficient Water Heaters. Joseph and his employee came out right on time, got to work with no fuss, and a little more than three or four hours later we had a brand new tankless installed in our house. They even swept up the garage cleaner than it was before they got there. Great communication before, during, and afterwards. Would definitely recommend them.”
“I'm so pleased with these guys. Very quick to pick up the phone, and got us scheduled right away for our new tankless water heater. The technician Marcos was super friendly and very receptive to some tough design challenges. It was important to me that the pipes were hidden in the walls, and he really went the distance to get it right, including working a very long day to install everything.”
“We texted EWH at 10pm and they called us right away! Our 10-year-old tankless water heater wasn't heating, and Marcus came out first thing the next morning. He had to order parts which came in the next day. He was back quickly to replace them and had our heater back to working. We are very impressed with this company — they are definitely very efficient and friendly too.”
“My new house had a tankless water heater without a descaling filter. Tried to call multiple places around but I did not get many responses back. Efficient Water Heaters had prompt and great communication, and I was able to book an appointment right away. Installation was done very quickly and professionally by Martin. I could not be happier!”
Reviews shown in customers' own words. We do not publish star ratings or aggregate ratings on this page.
Where Joseph works
Based in San Jose, the crew covers 19 cities from the South Bay up through the Peninsula.
San Jose + Santa Clara County
- San Jose
- Santa Clara
- Sunnyvale
- Cupertino
- Mountain View
- Milpitas
- Campbell
- Los Gatos
- Saratoga
- Los Altos
- Monte Sereno
- Palo Alto
San Mateo County / Peninsula
- Redwood City
- Menlo Park
- East Palo Alto
- Atherton
- Portola Valley
- Woodside
South Santa Clara County
- Morgan Hill
- Gilroy
- San Martin
Questions about the company
Talk to the specialist, not a call center.
Open 24/7 · Same-day service available · CSLB #1008381