Water heating – water dripping from vent or overflow tray

Cause

Temperature and pressure relief valve that is continually dripping 

Repair

  • every hot water cylinder requires a method of pressure relief because water expands with heat, increasing pressure. Occasional dripping is not a cause for concern – it just shows the system is working. If you turn off the power supply to the cylinder for 10–15 minutes and the dripping stops, then what you have is normal expansion of hot water

  • if dripping is continuous and excessive then there is a problem. Gently open the test lever to allow a discharge of water and any gritty material or minerals that may be contributing to the problem

  • if water doesn’t come out of the tank during this test, call a licensed plumber immediately

  • if water comes out during the test but dripping continues after the lever is closed, the valve may be faulty or worn out and requires replacement. This is not a task that a homeowner can carry out – call in a licensed plumber. You can check whether someone is licensed here

  • valve manufacturers typically suggest that homeowners operate the test lever once a year

Cause

Thermostat is set too high

Repair

  • water in a storage cylinder must be heated to over 60°C at least once a day to prevent the growth of Legionella bacteria. Water temperatures higher than this, however, can lead to risks of water from taps being dangerously hot and/or a waste of energy

  • check that the thermostat is set to 60°C. Reduce to this temperature of it is set higher

  • if dripping persists, call a licensed plumber

Cause

Leak at heating element

Repair

  • homeowners are permitted to remove and replace water heater switches, thermostats and elements in their own homes so long as it does not involve work on a switchboard. (The details are in the Electricity Act 1992 sections 79 and 80, and NZECP 51:2004 New Zealand Electrical Code of Practice for Homeowner/Occupier’s Electrical Wiring Work in Domestic Installations.) Landlords/ business owners cannot carry out electrical work in their rental properties or workplaces unless they hold the relevant licence

  • homeowners should only make this repair themselves if they have the skills, experience and tools to be able to safely and competently complete the job. You are required by law to carry out the work “in a workmanlike manner” and in compliance with all the relevant laws and codes

  • most homeowners should call a licensed plumber

  • the leak may be the result of a loose connection or faulty or badly installed element seals or washer

  • turn the power off and the water heater off and tighten the heating element

  • if leaking continues, turn the water and power off, drain the cylinder then remove the heating element and replace. Ensure you replace the old element with a new one of equal wattage. If the original element was 2kW, then the replacement element should also be 2kW and no higher

  • with very old cylinders, be aware that changes in pressure in the cylinder that come about from switching off, draining, refilling and switching on a tank again may potentially lead to stresses and a leak elsewhere, for example in a welded seam. In cases where a repair by a plumber may cost a quarter or a third of the cost of installing a new cylinder, carefully consider repair vs replacement. Replacement with a new cylinder must be carried out by a licensed plumber