When a hot water system suddenly stops working, a lot of homeowners immediately assume the worst.
The system is dead. Time for a replacement.
Sometimes that’s true.
But plenty of hot water problems are caused by individual components, valves or electrical faults that can often be repaired without replacing the entire unit.
We recently attended a property with no hot water at all.
After testing the system and its components, we found the hot water unit itself wasn’t the problem.
The fault was with the off-peak load control equipment supplying power to the system, so Energex was brought in to rectify the issue.
The customer didn’t need a new hot water system.
They needed the actual fault diagnosed.
Here are some of the more common problems we find that don’t automatically mean the whole system needs replacing.
1. A Failed Heating Element
Electric storage hot water systems use one or more heating elements to heat the water inside the tank.
Like any electrical component, an element can eventually fail.
When that happens, you might notice:
- completely cold water
- water that never reaches full temperature
- much slower recovery after showers
- a system that seems to run out of hot water unusually quickly
If the tank itself is still in good condition, replacing a failed element can often restore the system without replacing the entire hot water unit.
2. A Faulty Thermostat
The thermostat controls the temperature of the water and tells the heating element when to turn on and off.
If the thermostat fails, the system may stop heating properly even though the tank and heating element are otherwise serviceable.
Symptoms can include:
- no hot water
- inconsistent water temperature
- water not getting hot enough
- the system failing to reheat after use
A thermostat is a replaceable component.
Finding that the thermostat has failed doesn’t necessarily mean the hot water system itself has reached the end of its life.
3. A Problem With the Off-Peak or Controlled-Load Supply
This was the problem on our recent no-hot-water job.
Many electric storage systems operate on a controlled-load or off-peak electricity supply.
Instead of receiving power continuously, the hot water circuit is energised during particular periods.
If there’s a fault with the load control equipment or network supply, the hot water system may simply stop receiving the electricity it needs to heat the tank.
From the homeowner’s point of view, it looks exactly like a failed hot water system.
You turn on the shower.
Cold water.
But replacing the tank wouldn’t solve anything.
On this job, we tested the hot water system and traced the problem back to the off-peak supply. Energex was then called to rectify their equipment.
That’s why testing matters.
4. A Faulty Tempering Valve
Sometimes the hot water system is producing plenty of hot water, but you’re not actually getting it at the taps.
A tempering valve mixes hot water from the storage system with cold water before it reaches certain fixtures, helping keep the delivered temperature within a safe range.
If the valve develops a fault, sticks or becomes restricted, it can cause problems such as:
- lukewarm water
- fluctuating temperature
- reduced hot water flow
- water that seems much colder than it should be
That can make it appear as though the hot water system isn’t heating properly when the real problem is happening after the water leaves the tank.
In many cases, the valve can be serviced or replaced without replacing the hot water system.
5. Pressure Relief Valve Problems
Storage hot water systems use safety valves to control pressure as the water heats and expands.
The pressure and temperature relief valve, often called the PTR valve, is an important safety component.
Some discharge from these valves during heating can be normal.
However, constant or excessive leaking can indicate a problem involving:
- the valve itself
- excessive water pressure
- thermal expansion
- another part of the plumbing system
A faulty valve doesn’t automatically mean there’s anything wrong with the tank.
The important thing is determining why the valve is discharging rather than simply assuming the entire system needs replacing.
6. Electrical Supply, Circuit Breaker or Isolator Faults
Sometimes the hot water unit is perfectly capable of heating water.
It just isn’t receiving power.
Possible causes can include problems with:
- circuit breakers
- safety switches
- isolators
- electrical connections
- wiring
- controlled-load circuits
This is another reason no-hot-water faults need proper testing.
If the problem is somewhere in the electrical supply, installing a new hot water system may leave you with exactly the same problem.
Depending on where the fault is located, a licensed electrician or the electricity network provider may need to become involved.
7. Gas Ignition or Gas Supply Problems
Gas hot water systems have their own set of components that can fail without requiring complete replacement.
Depending on the type of system, a no-hot-water problem may involve:
- ignition components
- gas supply
- regulators
- valves
- burners
- sensors
- flow detection
- control components
A continuous-flow gas unit, for example, needs to detect sufficient water flow before it fires.
If something prevents that sequence from occurring correctly, the system may fail to produce hot water even though the main heat exchanger and other major components are still usable.
Again, diagnosis comes before replacement.
8. Blocked Filters, Strainers or Restricted Water Flow
Not every hot water problem is actually a heating problem.
Restrictions in the water supply can interfere with how a hot water system operates.
Depending on the system, problems can arise from:
- blocked strainers
- sediment
- restricted pipework
- faulty valves
- inadequate water flow
- pressure issues
These faults can produce symptoms such as poor hot water pressure, inconsistent temperature or a continuous-flow system failing to activate properly.
A relatively small plumbing issue can sometimes make an otherwise functional hot water system appear faulty.
So When Does a Hot Water System Actually Need Replacing?
There absolutely are times when replacement is the right option.
A system may be approaching the end of its useful life if:
- the storage tank itself is leaking
- corrosion has significantly affected the tank
- several major components are failing
- repair costs are becoming uneconomical
- the system is badly undersized for the household
- parts are obsolete or difficult to obtain
- repeated faults are occurring
- a newer system would provide a worthwhile efficiency improvement
The important point is that age alone doesn’t diagnose the fault, and neither does the symptom “no hot water”.
A ten-year-old system with a failed thermostat is a different problem from a ten-year-old system with a leaking tank.
One may need a relatively straightforward repair.
The other may genuinely need replacing.
Why Proper Diagnosis Matters
Hot water systems contain several components that all have to work together.
When one part fails, the symptom at the tap can look very similar regardless of what’s actually gone wrong.
That’s why we don’t think “no hot water” should automatically translate into “new hot water system”.
On our recent job, the system was tested before anything was replaced.
The result?
The fault wasn’t with the hot water system at all.
It was the off-peak load control supply, and Energex was able to take care of the problem.
That’s a much better outcome than replacing equipment that wasn’t broken.
Got a Hot Water Problem?
If your hot water has disappeared, isn’t getting hot enough, keeps running out or isn’t behaving normally, RJT Plumbing & Gas can diagnose the system and work out what has actually failed.
Sometimes replacement is the right answer.
But plenty of faults can be repaired.
The first job is finding out which one you’ve actually got.
Frequently Asked Questions
Does no hot water always mean I need a new hot water system?
No. Many hot water faults can be repaired without replacing the entire system. Common causes include failed heating elements, faulty thermostats, tempering valve problems, electrical supply faults, controlled-load issues, gas ignition faults and restricted water flow.
Can a failed heating element be replaced?
Yes. In an electric storage hot water system, a failed heating element can often be replaced if the tank itself is still in good condition.
Can a faulty thermostat cause no hot water?
Yes. A faulty thermostat can prevent the heating element from operating correctly, resulting in no hot water, inconsistent temperatures or slow recovery.
Can an off-peak electricity fault stop my hot water system working?
Yes. Electric storage systems connected to a controlled-load or off-peak electricity supply can stop heating if there is a fault with the supply or load control equipment. In these cases, the hot water system itself may be working correctly.
What does a faulty tempering valve do?
A faulty tempering valve can cause lukewarm water, inconsistent temperatures or reduced hot water flow even when the storage tank is heating correctly.
Does a leaking relief valve mean the hot water system needs replacing?
Not necessarily. A pressure and temperature relief valve may leak because of a faulty valve, excessive pressure or thermal expansion. The cause should be diagnosed before deciding whether the system needs replacement.
Can electrical faults cause a hot water system to stop heating?
Yes. Circuit breakers, isolators, wiring, controlled-load circuits or other electrical supply faults can stop a hot water system receiving power even when the unit itself is serviceable.
Can gas hot water systems be repaired instead of replaced?
Often, yes. Gas hot water faults can involve ignition components, regulators, valves, sensors, burners, flow detection or gas supply issues. Whether repair is appropriate depends on the age, condition and fault.
When should a hot water system be replaced instead of repaired?
Replacement may be appropriate when the storage tank is leaking, corrosion is advanced, repair costs are uneconomical, major components are repeatedly failing, the system is badly undersized or replacement parts are no longer practical to obtain.
