Can hot water systems explode?

Fast read

Hot water system explosions are very rare nowaday but can be very dangerous, with the risk of causing serious injuries. However, there are several modern safety mechanisms inbuilt in your hot water tank to prevent such accidents.

The most common cause of issues in hot water systems is a faulty pressure relief valve, which regulates the pressure within the hot water tank. If the valve leaks, it is a sign that the valve is stuck or that the components cannot handle the internal pressure and needs professional attention. Sediment buildup in the tank and DIY jobs, especially on the thermometer can also cause problems that may lead to a hot water system rupture.

To avoid these issues, routine maintenance is important, and any signs of malfunction such as failing pressure relief valve, abnormal noises, brown water indicating internal decay should be checked by a professional plumber.

Should I be worried about my hot water system exploding?

Although hot water system explosions are very rare, when they do occur, they can be dangerous. The force released can break through walls, with scalding water sometimes causing severe injuries. Nevertheless, several modern-day safety mechanisms prevent serious damage, so that this type of accident is literally impossible. So, there’s no need to sit in your home and wonder whether you are at risk of being seriously hurt each minute of the day. 

While it is very rare nowadays, there are several reasons your hot water system could rupture. So, look out for the signs explored below to know if you need to get your system looked at. 

What could be the causes of a rupture? 

Faulty pressure relief valve

The most common cause of issues of pressure built up in a hot water system is a blocked pressure relief valve. As the name suggests, this valve regulates pressure within the hot water tank. As a result of the natural heating process and the creation of vapours/steam, pressure in the tank builds up. Should the pressure inside the tank becomes too high, the pressure relief valve will release a certain amount of boiling water. But if this valve is broken, the pressure can build up, potentially leading to an explosion.

If you notice that your pressure relief valve leaks all the time or very frequently, it is most likely a sign that the part has become stuck or become faulty. It is also advisable to test and operate the pressure relief valve every 6 months just to check that it works. It is a simple test that can be performed by anyone. 

How to test if the valve is working properly?

Go to your hot water tank; on the side, there is a copper pipe that looks like a spout, as it is open at the end. It usually finishes  10  to 20 cm above the ground if outside. Up the top, where the pipe leaves the tank, is the location of the pressure relief valve. On top of it is a little hook, which allows you to test the valve. Push the hook/handle backwards till you hear water leaving the tank and spilling onto the ground. Be careful the water will be hot. 

Then let the handle go, and the valve should snap back into the close position. If the water continues to run after you let go, the valve is faulty, and you to to get it replaced. A faulty pressure relief valve can waste a lot of water over time and becomes expensive in regard to electricity costs and wasted water.  So if you notice this valve leaking, it is recommended that you get it professionally looked at.

hot water tank on the road
Electric hot water tanks usually have a lifespan of 10-plus years

Sediment build-up

Another cause for concern is sediment build-up in your hot water tank. If your tank is not maintained correctly and your water inlet brings sand and mud into the tank, sediment will be built up.  If tank flushing via regular use is not undertaken, sediment from the minerals in the water can build up at the bottom of the tank. This becomes a form of insulation, forming a crusty layer at the bottom of the tank that water could become trapped within. This could impact the ability of the tank to heat water. This problem can usually be identified through a popping sound; the popping sound from your tank indicates that sediment is collecting at the bottom and there is a potential for overheating. Furthermore, sediment can cause problems with the pressure relief valve by blocking the valve itself, potentially causing an increase in pressure in the tank. 

DIY jobs

DIY jobs are another problem that can cause a hot water system to rupture or even explode. While some Australians may believe that a standard hot water tank problem isn’t a reasonable excuse to contact their plumber, many unsuspecting homeowners may be caught off guard by a gas leak or a malfunctioning pressure valve without realising it. Replacing this valve or attending to a tank leak without professional help is never recommended. Furthermore, if you work on the system yourself, your tank system warranty is voided. 

Faulty thermostat

Each electric hot water system has an inbuilt thermostat, usually at the bottom of the tank, behind a square inspection cover. While in older electric hot water systems, one could set the temperature close to the boiling point, modern hot water tanks, even if in the hottest position, will only heat the water to about 65 degrees Celsius in order to avoid scalding, via the hot water outlet, especially in children. A thermostat that is faulty and doesn’t accurately measure the water temperature could cause the water to become overheated, leading to a build-up of pressure and if the pressure relief valve is blocked as well, then the risk of a tank explosion could theoretically occur. 

Corrosion and rust in the tank due to age

If the tank or its parts are corroded, usually on the bottom, where sediments can build up, they can weaken the tunk structure and fail under pressure. This will, over time, lead to a rupture and is the most common reason for a tank failure, usually around years 8 to 12. If your water heater is old and showing signs of rust or corrosion via brown water leaving the tank and coming through the tap, it might be time to speak to a professional about replacing it.

burst water pipe
Water pressure and temperature together create a force which can cause a rupture of the equipment

High water pressure

 High water pressure entering the tank increases the overall pressure inside the tank. Without a properly functioning pressure valve to relieve this pressure, there is a risk of an explosion. In modern water supply, it is highly unlikely your water pressure could reach a point where it could cause such damage. 

How can I avoid a potential risk? 

When it comes to preventing a water heater explosion, routine maintenance is the greatest defence. Your local plumber will check the pressure relief valve, the venting system and ensure that all parts, including any sacrificial anodes, are changed in time. 

It is also worth regularly checking on the system yourself between visits from the plumber. As mentioned above, you can self-test the pressure relief valve, check if your hot water suddenly has become much hotter, and monitor for signs of rust or corrosion.

If your water supply is very mineral or sediment heavy, a plumber could drain the tank every 4-5 years to remove sediment. You can also ensure via the thermostat setting that you keep the temperature of your water heater set to between 49-51 degrees Celsius. Such a temperature will help to reduce the risk of higher temperatures causing the water tank to expand and reduces the risk of pressure build-up. The only issue with setting the tank temperature a little lower is that your hot water capacity overall has been reduced a little, causing the system potentially to run out of hot water a little faster, in the case your family has three persons having a shower on after the other. 

Meanwhile, keep an eye on your tank’s functionality and consistency.

Important indicators that something is wrong are:

  • A pressure relief valve that is blocked or run constantly
  • Noises from the tank that are out of the ordinary
  • Decay, such as rust, leaks or cracks

By following these safety precautions and taking preventative measures, you can be assured that your hot water tank is unlikely to explode.

Should you consider purchasing a hot water solution, solar, batteries, or other renewable energy products, including car chargers, we recommend engaging with a qualified local supplier or installer to provide you with extensive advice. To find the right partner try our company finder and ask our recommended experts to assist you. Using a Your Energy Answer Authorised Partner will give you a well-vetted, experienced, reliable, and trustworthy company to serve your needs.

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