Your water heater headquarters. Tank, tankless, gas, and electric repair, replacement, and maintenance by Navien-certified, veteran-owned technicians. Flat-rate pricing. No surprises.
Your Water Heater HQ
Whether your hot water ran out this morning, your unit is leaking, or you're ready to upgrade to a tankless system, O5 Plumbing handles it all. We're certified by Navien one of the leading tankless water heater manufacturers and we service every major brand of tank and electric system too.
San Antonio's hard water takes a toll on water heaters faster than most homeowners realize. Sediment builds up on heating elements, anode rods corrode, and efficiency drops often years before the system finally fails. We diagnose the real issue first, then give you options at a flat price.
Annual maintenance extends the average water heater lifespan by 3-5 years and maintains peak energy efficiency year-round.
Gas Water Heaters
Tank and tankless gas systems repair, replacement, and new installs
Electric Water Heaters
Element replacement, thermostat repair, and full replacements
Tankless / On-Demand
Navien-certified installs. Endless hot water, lower energy bills
Annual Maintenance
Flush, anode rod inspection, and efficiency check all brands
What We Do
No cold water when you need it most, discolored water, strange noises, or a puddle under the tank we diagnose it right, give you a flat quote, and fix it the same day when possible.
When repair isn't the right answer, we help you choose the best system for your household's hot water usage and budget conventional tank or tankless. Pro-grade units with manufacturer warranties.
Navien-certified installation of on-demand systems. Tankless units produce hot water only when needed no standby heat loss, no 40-gallon tank to run dry, and a significantly longer lifespan than conventional units.
Know Your Options
Not sure which is right for your home? We'll assess your household size, usage, and existing setup then give you a straight recommendation.
Why O5
O5 is the only Navien-certified plumber in the area you'll find that also does flat-rate pricing. That means you get the expertise of a manufacturer-trained technician and the assurance of knowing the number before we pick up a single tool.
We also don't sell you a new unit when a repair will do. If your water heater has life left in it, we'll tell you and fix it for less than a replacement.
Request a QuoteFactory-trained on the leading tankless systems proper sizing, install, and diagnostics.
Accountability and integrity on every job the same standards we held ourselves to in service.
After the scope is clear, you approve the quote before work begins. No hourly billing that climbs while we work.
Same-day service when available. When your hot water goes out, we don't make you wait until next week.
Current Offers
Current Offer
Install or replacement tank or tankless. Mention this offer when booking.
Claim OfferAvailable
Active duty, reservists, veterans, and military families. Thank you for your service.
Claim OfferAvailable
For senior citizens on any water heater service or installation. Restrictions apply.
Claim OfferCannot combine offers. One-time use. Subject to availability.
Customer Reviews
"Quick response on a Sunday morning when our water heater went out. They had a tech at the house within a couple of hours, replaced the unit, tested everything, and walked me through the warranty. Fair price for weekend work couldn't ask for more."
Steve P.
Cibolo • Water Heater Replacement
"Eric and his team installed our new water softener and tankless heater. They explained the sizing for our house, gave a straight number, and stuck to it. The workmanship is excellent you can tell they take pride in it."
Nancy B.
Garden Ridge • Tankless Install
"Called about a leaking water heater on a Tuesday morning. They gave me a quote over the phone after a few questions, showed up in the afternoon, and installed the replacement in about two hours. No mess left behind. Exactly the quoted price."
C. Rodriguez
Stone Oak • Tank Replacement
Common Questions
Ready?
Call us and we'll diagnose the issue, give you options, and get it handled often the same day. Ask about current offers and financing.
Mon-Fri 7:30 AM - 6:00 PM • Sat 8:00 AM - 5:00 PM • Same-day service when available
