Tankless descaling and annual flush in San Jose
Hard water scales a tankless heat exchanger faster than most owners expect, and a flush restores the flow and protects the unit.
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- Phelan Ave San Jose office
- Tank, tankless, heat pump
Perfect Tankless Plumbing, San Jose, CA
Tankless descaling in San Jose circulates a descaling solution through the heat exchanger for about an hour using the unit's isolation valves, then flushes it, cleans the inlet filter and checks the error history; San Jose water runs roughly 10 to 16 grains per gallon, so an annual flush is a sensible baseline.
Updated September 2026
Water Heaters
Why tankless units need descaling
When hard water is heated, calcium and magnesium drop out as scale. In a tankless unit that happens inside a narrow heat exchanger, where even a thin layer reduces heat transfer and flow. The symptoms are lukewarm water, temperature swings and eventually a scale or overheat error.
Descaling dissolves that layer. Done regularly, it keeps the unit running at its rated output and avoids the kind of scale damage that shortens a heat exchanger's life.
Included
What the annual service includes
- Heat exchanger descaling
- Inlet filter cleaning
- Error history review
- Burner and flame sensor check
- Air intake screen cleaning
- Venting and condensate inspection
- Outlet temperature test
Isolation valve retrofit
Flushing a tankless unit properly needs isolation valves with service ports on the hot and cold lines. Many older installations were done without them, which makes descaling awkward or impossible without cutting pipe. We retrofit a valve kit so the unit can be isolated and flushed in minutes, now and every year after. It is a one-time part that turns every future service into a short, clean job and lets the owner see exactly where the maintenance connects, which matters for anyone who wants to flush the unit themselves between our visits.
Inlet filter cleaning
Every tankless unit has a small screen on the cold water inlet that catches grit and scale flakes before they reach the heat exchanger. When it clogs, flow drops and the unit may not fire for small draws. We remove and clean it during each flush, check it for damage, and replace it if the mesh is torn. On homes with heavy sediment we may suggest a whole-house sediment filter so the screen does not clog between visits and restrict flow to the heater again within a few months.
Annual service visit
An annual visit covers more than the flush. We read the error history, check the burner and flame sensor, clean the air intake screen, inspect the venting and condensate line, confirm the gas pressure is within range, and test the outlet temperature. Small issues found early, a partly blocked condensate trap or a loose vent joint, are cheap to fix and prevent the no-hot-water call in the middle of winter. We leave a short written note of everything checked, so you have a service record if the manufacturer ever asks for one.
Local context
San Jose's hardness and tankless maintenance
Published guidance on San Jose water puts hardness at roughly 10 to 16 grains per gallon depending on the season and the blend of Sierra water and valley groundwater, which is firmly in the hard to very hard range. That seasonal swing is why two neighbors with the same unit can need descaling on different schedules. An annual flush is a sensible baseline here, and homes with a softener upstream can usually stretch it further.
How the job runs
How a descaling visit runs
- 1
Shut off and isolate
Power off, valves closed.
- 2
Connect the pump
Hoses on the service ports.
- 3
Circulate the solution
Through the heat exchanger for about an hour.
- 4
Flush clean
Fresh water until it runs clear.
- 5
Clean the inlet filter
Replace if damaged.
- 6
Restart and test
Temperature, flow and error history.
DIY or call
Tankless maintenance you can do
| Task | Reasonable to DIY | Call a plumber |
|---|---|---|
| Cleaning the inlet filter | Yes, with valves closed | If it is damaged |
| Descaling with a kit | Handy owners with service valves | No valves fitted |
| Clearing the air intake screen | Yes | If errors continue |
| Reading error codes | Yes | To diagnose them |
| Adjusting gas pressure | No | Always |
| Fixing venting | No | Always |
Cost factors
What a descaling visit costs depend on
We do not publish a local descaling price; whether valves are already fitted sets most of it.
- Isolation valves. already fitted or retrofitted
- Scale severity. heavy scale needs a longer cycle
- Filter condition. cleaned or replaced
- Annual checks. burner, venting and condensate
- Number of units. racked systems take longer
- Parts found worn. sensors or igniters
FAQ
Tankless Descaling and Flush questions from San Jose homeowners
Once a year is a sensible baseline with local hardness, less often with a softener.
Scale reduces flow and heat transfer, triggers errors and can damage the heat exchanger.
We retrofit a valve kit so it can be flushed now and every year after.
It reduces scale a lot, but an occasional flush and filter check is still worthwhile.
Usually around an hour and a half.
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From our guides: Read the guide on tankless goes cold, Hard Water and Your Water Heater in San Jose, CA, How Often to Flush a Tankless Water Heater in San Jose, Softener or conditioner, explained, Read the guide on rinnai error codes, Read the guide on navien error codes.
One number, any hour
Book your tankless flush
Call to schedule descaling and a full annual check.
