A tankless water heater is one of the better long-term investments in a Santa Cruz home — lower energy bills, endless hot water, and a lifespan that can reach 20+ years when the unit is properly maintained. That last part is where most owners fall short. Tankless units need less maintenance than conventional tank heaters, but they do need maintenance, and in Santa Cruz’s water conditions, skipping it has real consequences.
This guide covers everything involved in maintaining a tankless water heater: what tasks matter, how to do them, how often, and which ones are DIY-appropriate versus worth handing to a professional.
Why Maintenance Matters More in Santa Cruz
The single biggest threat to a tankless water heater’s longevity is mineral scale buildup inside the heat exchanger. When hard water — water with elevated calcium and magnesium content — is heated, those dissolved minerals precipitate out of solution and deposit on the surfaces they contact. In a tankless unit, that means the interior of the heat exchanger: the component that transfers heat from the burner to the water flowing through the unit.
Scale is an insulator. As it builds up on the heat exchanger walls, the unit has to work harder and run longer to achieve the same water temperature. Energy efficiency drops, the burner runs hotter, and mechanical stress on components increases. Left unchecked, scale buildup is the most common cause of premature heat exchanger failure — the most expensive repair a tankless unit can require.
Santa Cruz County’s water supply has enough dissolved mineral content to make this a genuine annual concern, not a theoretical one. Homeowners in areas closer to the mountains (Felton, Boulder Creek, Scotts Valley) tend to deal with harder water than those in the city proper, but scale accumulation affects tankless units throughout the county. If you’ve ever noticed white or chalky deposits around faucet aerators or showerheads, your water is hard enough that annual descaling is not optional.
The Annual Descaling Flush
Flushing the heat exchanger with a descaling solution is the most important maintenance task for a tankless water heater, and the one that most directly extends the unit’s life. It should be done once a year in most Santa Cruz homes — or every six months if your water is particularly hard or your household uses significant hot water volume.
What You’ll Need
- White vinegar (food-grade) or a commercial descaling solution designed for tankless water heaters
- A small submersible pump (available at hardware stores for under $30)
- Two washing machine hoses or similar flexible hoses
- A 5-gallon bucket
- Isolation valves on the unit’s service ports (most modern tankless units have these; if yours doesn’t, a plumber can add them)
The Process
1. Shut off the gas or power supply to the unit. For a gas unit, turn the gas valve to the off position. For an electric unit, turn off the circuit breaker. Do not skip this step.
2. Close the cold water inlet valve and the hot water outlet valve. These are typically the main shutoffs on either side of the unit. Closing them isolates the heat exchanger from the rest of your plumbing system.
3. Open the service port valves (isolation valves). These are smaller valves — usually with a different handle style — that provide access to the heat exchanger loop. Connect hoses to the cold water service port and the hot water service port.
4. Set up the pump and bucket. Place both hose ends into the 5-gallon bucket. Fill the bucket with the descaling solution — either undiluted white vinegar or the commercial solution diluted per its instructions. Put the submersible pump in the bucket on the inlet side.
5. Run the pump. The pump circulates the descaling solution through the heat exchanger in a closed loop: from the bucket, through the cold water service port, through the heat exchanger, out the hot water service port, and back into the bucket. Run for 45 minutes to one hour. For a unit that hasn’t been descaled in several years, extend to 90 minutes.
6. Flush with clean water. Drain the descaling solution from the bucket and refill with clean water. Run the pump for another 5–10 minutes to flush residual solution from the heat exchanger.
7. Close service port valves, reconnect supply lines, reopen inlet and outlet valves. Restore gas or power. Run a hot water tap briefly to purge any air from the system before returning to normal use.
If your unit doesn’t have service ports: This procedure isn’t possible without them. A plumber can install isolation valve service ports during a maintenance visit, which makes future annual descaling straightforward. It’s a worthwhile one-time addition to any tankless unit that was installed without them.
When to Call a Professional Instead
DIY descaling is manageable for most homeowners, but there are situations where professional service makes more sense:
- The unit is throwing error codes related to flow rate or the heat exchanger
- It’s been more than two or three years since the last flush — heavily scaled units benefit from a professional assessment before and after cleaning
- You’re not comfortable working around gas connections or the unit’s plumbing
- The unit is a high-output commercial or whole-house model with more complex service requirements
A professional maintenance visit also typically includes the other checks covered below, which is an efficiency advantage over a DIY flush alone.
Inlet Filter Screen Cleaning
Most tankless water heaters have a small filter screen on the cold water inlet that catches sediment and debris before it enters the unit. In areas with older plumbing or any sediment in the water supply, this screen can restrict flow if not cleaned periodically.
Cleaning it is simple: close the cold water inlet valve, remove the screen (usually by unscrewing a cap or plug), rinse it under running water to clear debris, and reinstall. This takes about five minutes and should be done at least annually, or more often if you have older galvanized supply pipes that shed rust particles.
A clogged inlet screen reduces flow rate, which can trigger low-flow error codes on the unit and cause inconsistent water temperature.
Condensate Trap Cleaning (Condensing Units Only)
Condensing tankless water heaters — the high-efficiency models with two exhaust pipes — produce condensate as a byproduct of their combustion process. This acidic condensate drains through a trap to a floor drain or condensate line. The trap prevents sewer gas from entering the unit.
If you have a condensing unit, the condensate trap should be checked and cleaned annually. A clogged trap can back up condensate into the unit, causing error codes and potential damage. Cleaning involves removing the trap, flushing it with water, and reinstalling. Check your owner’s manual for the specific location on your model.
Venting Inspection
Gas tankless units vent combustion gases through a dedicated flue pipe, typically to the exterior through a side wall. The vent termination — the cap or cover on the outside of the house — should be visually inspected annually for blockage. Birds occasionally nest in or near vent terminations, and debris from nearby vegetation can accumulate.
A blocked vent is a safety issue, not just a maintenance one. Most units have sensors that will shut the unit down if a vent blockage is detected, but physically checking the exterior termination takes less than a minute and is worth doing.
Also visually inspect accessible sections of vent pipe inside the home for corrosion, gaps at joints, or signs of condensation dripping — all of which warrant a service call.
Exterior and Component Inspection
Once a year, give the unit a quick visual inspection:
Check all connections for moisture. Any dampness at water connections, the pressure relief valve outlet, or condensate drain points warrants investigation. Small drips at fittings are sometimes just loose connections, but corrosion at fittings on older units in coastal locations can indicate the beginning of a more significant problem.
Check the pressure relief valve. The T&P (temperature and pressure) relief valve is a safety device that releases pressure if the unit overheats or over-pressurizes. It should have a discharge pipe pointed down toward the floor. Inspect it visually for corrosion or dripping. A valve that’s dripping constantly is either faulty or responding to an actual pressure issue — either way, have it looked at.
Check for error codes. Most modern tankless units display diagnostic error codes when something is off. Note any codes and look them up in the owner’s manual, or mention them when scheduling service. Error codes caught and addressed early typically indicate minor issues; the same codes ignored for months can indicate escalating damage.
Annual Maintenance Schedule Summary
For most Santa Cruz homes with a tankless water heater:
Every year:
- Descaling flush (every 6 months if water is very hard or household use is high)
- Inlet filter screen cleaning
- Condensate trap cleaning (condensing units)
- Vent termination visual inspection
- Exterior and connection visual inspection
- Error code check
Every 3–5 years:
- Professional service inspection, including burner and igniter check, flow sensor test, and full system assessment
The 3–5 year professional visit catches the kinds of component wear that isn’t visible during a DIY maintenance pass — burner degradation, igniter wear, flow sensor drift — before they become failure events.
Signs Your Tankless Unit Needs Service Now
Beyond the scheduled maintenance tasks, these are signals that something needs attention regardless of where you are in the maintenance calendar:
Inconsistent water temperature. Water that fluctuates between hot and lukewarm, or takes longer than usual to reach temperature, often indicates scale buildup in the heat exchanger or a failing flow sensor.
Reduced flow rate from hot taps. A partially blocked inlet filter or scale-related flow restriction can reduce hot water pressure throughout the house.
Error codes on the display. Don’t ignore these. Most codes are documented in the owner’s manual with recommended actions.
Unusual sounds. Tankless units make some noise during operation — the burner igniting, the fan running — but knocking, clicking that doesn’t resolve on ignition, or sounds you haven’t heard before warrant a service call.
Unit failing to ignite. If the unit attempts to fire and fails — typically signaled by an error code and no hot water — the igniter, gas supply, or venting may be the cause. This is a professional call, not a DIY diagnosis.
Professional Tankless Service in Santa Cruz
Eco-Flow Plumbing Inc. services all major tankless water heater brands throughout Santa Cruz County — including Santa Cruz, Live Oak, Aptos, Capitola, Soquel, Scotts Valley, Seabright, Felton, Boulder Creek, and Watsonville. We handle annual maintenance visits, descaling, filter cleaning, and repairs — and we install isolation valve service ports on units that were set up without them.
For anything related to water heater repair and installation, we’re the local team.
Contact Eco-Flow Plumbing to schedule tankless water heater service. Or call directly: (831) 818-6331.
