A six-monthly relief valve check and an annual service, with a monthly temperature check. The operation and maintenance guidance in the plumbing standard has the temperature and pressure relief valve's easing lever lifted briefly every six months to confirm it flows and reseats, and a valve that weeps afterwards replaced. Once a year a licensed plumber (and gasfitter for gas units) services the unit: relief valve, thermostat, anode condition, flue and burner or element, tank flush. The sacrificial anode is replaced at three to five years per the manufacturer, and the relief valve is commonly replaced at five years. A monthly check that stored water is at 60 degrees or above, and the delivery temperature at the furthest outlet, is recommended practice as the Legionella control point for stored hot water.
The intervals
| Interval | What happens | Who |
|---|---|---|
| Monthly (recommended practice) | Storage temperature confirmed at 60 degrees or above, the Legionella control point for stored hot water, and delivery temperature at the furthest outlet; any leak or discharge from the relief drain noted. | Owner or staff |
| Six-monthly | The temperature and pressure relief valve's easing lever lifted briefly to confirm it flows and reseats; a valve that weeps afterwards is replaced. The step the plumbing standard's operation and maintenance guidance sets. | Owner or staff, or the plumber |
| Annual | Service by a licensed plumber (and gasfitter for gas units): relief valve, thermostat, anode condition, flue and burner or element, tank flush; tempering valve or TMV tested at the same visit. | Licensed plumber |
| Three to five years | Sacrificial anode replacement per the manufacturer; the relief valve commonly replaced at five years. | Licensed plumber |
Who does it and what to keep
A licensed plumber, with a gasfitter's licence for gas storage units and the TMV endorsement where the outlets are tempered. The record is the service report for each unit with the temperatures measured, the relief valve result, the anode condition and the parts replaced, kept with the unit's installation and warranty documents. Where the building is a care setting the temperatures go into the water safety plan. A unit that has never had its anode replaced is usually found when the tank fails, which is why the anode date belongs in the register.
The rule behind the interval
AS/NZS 3500.4 Plumbing and drainage, Part 4: Heated water services, is the installation standard; its operation and maintenance appendix sets the six-monthly relief valve check and the annual service as the maintenance routine. The 60 degree storage temperature and the 50 degree outlet limit (45 in some care settings) come from the same standard and the enHealth Legionella control guidance. The manufacturer's instructions set the anode and relief valve replacement intervals. Gas units are serviced under the gas installation rules by a licensed gasfitter.
Common questions
Why 60 degrees in the tank?
Legionella grows between about 20 and 45 degrees and is killed above 60. The tank is kept hot and the outlets are tempered down to 50 degrees (or lower in care settings) by a tempering valve or TMV, so the storage temperature and the outlet temperature are checked as two separate things.
What if the relief valve keeps discharging?
A relief valve that drips continuously is either failed or is doing its job against excess pressure or temperature. It is not capped or plugged; the plumber finds the cause and replaces the valve if it will not reseat.
Put it in the register
An interval only holds when the asset is listed with its tasks, its contractor and where the record lives. Standara's library carries this asset with the tasks above attached, so adding it to a site's register produces the year's schedule, the monthly to-do list and the completion record the auditor or insurer asks for. The fuller picture, with the neighbouring assets and the rule behind each interval, is in the Water systems testing schedule.
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- A worked example: one club's register, planner and records for a year
- All guides and answers