How often depends on your heater's manual. Bradford White's commercial gas manuals call for a monthly sediment drain, a tank cleanout every 3 months in hard water, and a yearly inspection by a qualified technician. That includes the relief valve, anode and vent. Maricopa County recommends annual service and manufacturer descaling.
The schedule in the manuals
Bradford White's gas-fired commercial manual has a maintenance section that lists intervals. It says a qualified service technician should perform the work "at the minimum periodic intervals suggested below," and that "in some installations, the maintenance interval may be more frequent depending on the amount of use and the operating conditions of the water heater." The list boils down to this:
| How often | Job |
|---|---|
| Monthly | "Drain off a gallon of water to remove silt and sediment." |
| Every 3 months, in hard water | Drain the tank and clean out the deposits through the cleanout opening |
| Every year | Check ignition systems, temperature controls and safety shut-off valves |
| Every year | Remove the burner rack and clean orifices and ports |
| Every year | Check the temperature and pressure relief valve for lime |
| Every year | Inspect the anode rod |
| Every year | Inspect the venting system for leakage |
The manual also says the heater "should be inspected at a minimum annually by a qualified service technician for damaged components and/or joints not sealed."
Bradford White's high efficiency commercial manual has a similar table. It lists a one-month interval for tank sediment removal ("drain off several gallons of water") and a one-year interval for the powered anode system, the relief valve function test, the vent and air intake system, the vent terminals and the combustion system. It says that "water heater maintenance includes monthly tank flushing and cleaning and removal of lime scale."
### What "hard water conditions" means
The cleanout step is tied to hard water. The manual says "if this water heater operates under hard water conditions, the following should be performed at least every 3 months." The steps are to drain the water heater and remove the cleanout jacket cover and tank cover. It adds a warning that matters: "care must be taken to avoid trying to break deposits loose as this could damage the glass lining and shorten the life of the water heater."
The City of Phoenix reports hardness of 10 to 17.6 grains per gallon, which Penn State Extension calls "very hard" above 10.5. Our page on how hard Phoenix water is explains the number. That puts a Phoenix heater in the range where the manual's hard water schedule applies. The county reaches the same view for the whole county. Its guide says "due to the hard water quality in Maricopa County, it is highly recommended that a water softener or water filter be installed to extend the life of a water heater unit."
How to tell when it needs cleaning
Manuals also give a way to measure the buildup instead of guessing. The high efficiency manual says "the depth of the buildup should be measured periodically." It says a tank has about 3 inches of lime when the level reaches the bottom of the cleanout opening, or about 1 inch if it has reached the drain valve opening. It adds that "a schedule for deliming should be set up, based on the amount of time it would take for a 1/2 in (1.3 cm) buildup of lime."
That is a better method than a calendar alone. Say the half-inch mark shows up after four months. Then the schedule is every four months. Lime "reduces the life of the equipment" and "reduces efficiency of the water heater and increases fuel consumption," according to the same manual. Our page on whether hard water ruins a hot water heater covers the damage in more detail.
What Maricopa County says
The county's Hot Water Supply Requirements guide is written for permitted food businesses. It is less specific than the manual. It says "it is highly encouraged that descaling and routine maintenance be performed as recommended by the manufacturer" and "consider installing water filters and/or softeners." In its buying advice, it adds: "it is recommended to have the water heater serviced annually by a qualified technician." So the county's schedule is the manufacturer's schedule plus a yearly technician visit.
### A softener changes the anode schedule
If the building has a softener, the anode needs closer watching. The gas-fired manual says "the use of a water softener may increase the speed of anode consumption. More frequent inspection of the anode is needed when using softened (or phosphate treated) water." The high efficiency manual adds that softening equipment "does not always remove all of the hardness (lime)," so "it is recommended that a regular schedule of deliming be maintained." Our page on whether salt-based softeners damage a water heater covers the anode check.
Who does which job
A manager can do the small, frequent job. A technician should do the rest.
- 1Monthly sediment drain. The manual gives one gallon or several gallons depending on the model. The water "may be HOT," so use a hose and keep people clear.
- 2Quarterly cleanout in hard water. This means opening the tank, so it is a technician's job. The manual asks for care not to damage the glass lining.
- 3Yearly inspection. The manual calls for a qualified service technician to check the controls, safety valves, burner, anode, relief valve and vent. Gas combustion and venting are safety items.
- 4Relief valve. The manual says to "lift the lever at the top of the valve several times until the valve seats properly without leaking." If it drips afterward, see our page on a leaking pressure relief valve.
- 5After a long shutdown. The manual warns that a heater left unused for "generally two weeks or more" can build up hydrogen gas. It recommends opening the hot water faucet "for several minutes" before using any electrical appliance on the hot water system, and keeping flames away from the faucet while it runs. That matters for a closed suite or a seasonal restroom.
Keep a log. Write down the date, who did the work and what was found. A log shows whether buildup is outrunning the schedule. It is also the first thing a technician will ask for. If a heater has no log, the first visit is a good time to start one and to note the tank's condition and the anode's state.
Tankless and other types
These schedules are for storage tank heaters. Tankless heaters have their own scale procedure. Bradford White's tankless manual has the unit flash an "LC" code when the heat exchanger needs flushing and says "failure to flush the water heater when 'LC' is flashing will cause damage to the heat exchanger." Our page on how often to descale a tankless heater in Phoenix covers that. For the wider picture, see what a commercial plumbing preventive maintenance plan includes and types of commercial water heaters.
HQ Plumbing & Air is licensed and insured, and can service your heater to the manual for your model and tell you what the tank looks like inside. We offer free estimates and upfront pricing.