Keeping your water heater in good condition isn’t hard when you know what causes too much pressure in a hot water heater. In this post, you will learn what causes high water heater pressure, what signs to look for, and what to do if you have too much pressure in your hot water heater. 

Works Plumbing is Pacifica’s expert water heater repair team. We are available 24 hours a day for emergency plumbing repair.

Indications of High Pressure 

It’s normal for pressure to build up in your hot water tank. As water heats up inside your water heater, it goes through thermal expansion. Hot water takes up more space than cool water. 

Pressure in your hot water heater builds as water experiences thermal expansion. If unreleased, your water heater may sustain damage. If you don’t know the signs of high pressure in your water heater, you won’t know when to take action.

Here are some indicators of high pressure:

Discolored water:  If your water doesn’t run clear, it could indicate a few things, including high pressure in your hot water heater. If you notice discolored water, observe your water heater for additional signs of high pressure.

New Noises: You know the sounds your hot water heater typically makes. If you notice new noises like popping or hissing, your water heater may have too much pressure.

Signs of Wear:  Examine your hot water heater. If you see any pooled water or signs of rust, your water heater needs attention from a qualified professional. Water leaking from your hot water heater can result in extensive water damage if left untreated.

Essential Parts of a Hot Water Heater

When you examine your water heater for signs of high pressure, you need to know what parts could contribute to the problem.

A typical water heater looks like a big metal canister with a heating element that heats the water stored inside the water heater. The thermostat communicates with the heating element to maintain the temperature. When the water reaches the determined temperature, the thermostat tells the heating element to discontinue heating.

The pressure relief valve detects the pressure level within the hot water heater and opens to release pressure as necessary. If any of the essential parts becomes damaged, it could contribute to a dangerously high level of pressure within your hot water heater.

Causes of High Pressure in a Hot Water Heater

Now that you know the signs to look for, we can determine what causes too much pressure in a hot water heater. Understanding the causes will help you determine when to call a professional plumber for maintenance. 

The Thermostat Is Too High

If the hot water heater thermostat is set too high, pressure will build up in the tank. Any temperature greater than 120 degrees can cause damage to your hot water heater. When you adjust the thermostat to a safe level, the hot water heater can function optimally. 


Your water supply contains a variety of sediment and minerals. Over time, these minerals, like calcium, stick to the inside of your water heater. As minerals build up, so does the pressure inside your tank. 

Flushing your hot water heater can remove mineral deposits and restore a safe pressure level in your hot water heater. If mineral buildup is a problem throughout your home, a professional plumber can install a filter to remove minerals as they enter your plumbing system.

Faulty Pressure Relief Valve

The pressure relief valve is responsible for releasing pressure from your hot water heater when it gets too high. If there is a problem with the pressure release valve and it does not open when it needs to, pressure will build up in your hot water heater. 

Water pooling around your hot water heater indicates a problem with the pressure release valve. To make sure your pressure release valve is always in working order, it needs regular maintenance. Without routine inspection and testing, the pressure relief valve could become damaged. 

You Have the Wrong Type of Water Tank for Your Plumbing System

If you have a closed plumbing system, your hot water heater should have an expansion tank to allow room for thermal expansion without causing pressure buildup in your hot water heater. 

All closed plumbing systems require an expansion tank. If you have a closed plumbing system and no expansion tank, your system was improperly installed. Call a professional plumber right away.

Damaged Heating Elements

If your thermostat is set too high, the heating elements may become damaged. You may notice inconsistencies with the water temperature as the heating elements surge and then short out. A qualified professional should complete any maintenance on the electrical components of your hot water heater.

Incoming Water Supply

Sometimes, pressure buildup in your hot water heater comes from a source outside your home. If your city’s water supply is high pressure, that can affect the pressure in your hot water heater.  

Your water heater could sustain damage from high city water pressure even if you do everything right. That’s why regular maintenance by a professional is essential in extending the life of your hot water heater.

The Dangers of Ignoring Pressure Buildup

The longer you put off water heater maintenance, the more damage high pressure can cause. Damage caused by pressure buildup can hurt your plumbing, your family, and your wallet.

Skyrocketing Energy Bills

When your hot water heater operates in a compromised state, you will see it reflected in your water and electric bills. A leaky water tank contributes to a high water bill, and damaged components will cause your water heater to use more electricity than normal as it heats the water. 

If you experience high utility bills because of a worn-out water heater, consider upgrading to an energy-efficient model. Newer hot water heater options require less electricity to operate than older water heaters.

Water Tank Failure

Ignoring high pressure in your hot water heater could end up damaging your water heater beyond repair. If addressed early, you can remedy high water pressure before it turns into an expensive repair or replacement bill. 

Plumbing Damage

High pressure in your water tank can affect your plumbing. If not addressed, high pressure can cause wear on your pipes; eventually, they may burst. A burst pipe can cause extensive water damage, and structural damage caused by a water leak is very expensive to repair. 


When pressure builds up due to a thermostat malfunction, your hot water heater cannot regulate the temperature of the water. Inconsistent water temperature could result in severe burns while showering or even washing your hands. Small children are especially at risk of sustaining burns due to water heater malfunction.


While uncommon, it is possible for a hot water heater to explode. The longer a water heater works under high pressure, the higher the chance of explosion. 

When You Notice High Pressure

If you notice signs of high pressure in your water heater, use extreme caution as you troubleshoot the cause of the high pressure. If you feel uncomfortable locating the cause of high pressure, call a professional plumber right away.

Unplug your hot water heater to allow some pressure to release while you inspect the hot water heater.  

The first thing you should do is check the pressure relief valve. If the pressure relief valve is leaking, that means the valve opened to release pressure, which is a good thing. Adjust the pressure relief valve carefully to lower the pressure in your hot water heater.

If the pressure relief valve opens often, you have ongoing high pressure and may have a problem elsewhere. If you release some pressure using the pressure relief valve, but high pressure is still a problem, check the thermostat to ensure the temperature is not set above 130 degrees. 

Keep in mind that attempting to repair any electrical appliance yourself is risky and could result in electrocution. The safest course of action is always to contact a professional plumber to schedule a maintenance appointment. 

Avoiding High Pressure

A variety of factors contribute to high pressure in your hot water heater. The older your water heater, the more likely you are to experience high pressure. Over time, parts of the water heater begin to wear and eventually need replacement. 

A professional plumber should inspect your hot water heater at least once per year. During the inspection, the technician will flush the buildup from inside the water heater, ensure all pipes are in working order, and check all components for damage.

Professional Maintenance

What causes too much pressure in a hot water heater is less of a question when you take good care of your water heater. If you enjoy home improvement projects, you can try flushing the water heater on your own. If you are uncomfortable with doing your own hot water heater maintenance, don’t hesitate to call a professional. 

Works Plumbing in Pacifica, CA, offers 24/7 service for all plumbing emergencies. Call our team today at 650-414-7261.

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