Can A Bad Water Heater Cause Low Water Pressure?

Low water pressure is an aggravating problem. Perhaps you climbed into your shower, hoping to take a toasty rinse under the powerful water stream to wash away the day’s troubles, only to be disappointed by poor water pressure. You might notice the problem persists only with the hot water (it can be with the cold water too), so you decide to consider the water heater as a culprit. 

Maybe it’s been a few years since the last service visit, so the heater has sat in the dark corner of a maintenance room, untouched for years on end. After all this time, there’s a possibility it’s giving you grief with the water pressure in your home. But, before you replace it with a new and improved heater, here’s what you should know.

Water Pressure vs. Water Flow

Many folks confuse water pressure and water flow rates. We get it – they’re similar, and both refer to the water streaming out of the fixtures and appliances in your home. However, while they both apply to water in your home, they’re not the same. 

Water pressure refers to the energy or force applied to the water to whisk it through the water lines. Many times, the amount of water pressure you have is the result of gravity at work. So, the pressure is how forcefully it comes out of the faucet. 

On the other hand, water flow is how much water flows through the pipe at a time. Generally, this is measured in gallons per minute (think of kitchen faucets, such as those with a 2.2 GPM flow rate). 

Sometimes, the flow rate is reduced, causing people to assume there’s a problem with the water pressure. In other cases, the water pressure is reduced, making people think there’s an issue with the flow rate. So, while these two are intertwined and directly impact the other, they’re not the same.  

Can A Water Heater Going Bad Cause Low Water Pressure?

A failing water heater can cause low water pressure issues in your home, but sometimes, the heater isn’t failing at all. Sometimes, it’s as simple as having the unit serviced (especially if it hasn’t been in a while). So, before you write off your water heater as faulty, have a professional plumber inspect and service the unit.

Sometimes, the water heater might be on its last leg, so a replacement is necessary in the near future. It might be reaching the end of its lifespan, but it could be a simple issue. 

What Causes A Water Heater To Fail?

Like any other home appliance, water heaters don’t last forever. Eventually, they give out, usually due to failed components in the system, such as the thermostat, temperature and pressure valve, or the gas control valve or heating coils.

The most common causes of failure in a water heater include:

  • Internal rust: Metal rods in your water heater help prevent corrosion, but these rods require replacement over time. If they’re not replaced periodically, rust can take over, causing issues with the system.
  • Buildup of sediment: Homes with hard water likely experience issues throughout, including problems with the water heater. Mineral deposits can build up in the tank, eventually settling to the bottom in thick sediment. This can cause issues with the heater, potentially causing it to fail. 
  • Corrosive fumes: For combustion to occur, water heaters require air intake. If the air quality is poor (such as corrosive air), it can eventually lead to unit failure. 
  • High water pressure: Excessive water pressure can damage various appliances in your home, including your water heater. If the pressure remains high for too long, this can overtax the system, causing it to fail. 
  • Improper sizing: If your water heater is too small, it’ll have to work overtime to keep up with demands. Eventually, this overtime will catch up to the unit, causing it to fail prematurely. 
  • Old age: After a while, the major components in the unit will begin to fail. While you might be able to replace specific parts, the larger elements will be more costly to fix. In some cases, fixing the unit might be more expensive than investing in a new one. 

Possible Reasons Behind Low Water Pressure Due To A Water Heater

Your water heater could be the culprit causing your water pressure issues. Generally, when the water heater is behind these problems, one of three things is going on. Here are the most common causes of low water pressure as a result of water heater issues:

Partially Closed Shut-Off Valve

On your water heater, you’ll find a shut-off valve. This valve might be partially closed in some cases, restricting water flow from the pipe. This can cause low water pressure, so it doesn’t hurt to check (especially since it’s a simple fix).

Sometimes, you might accidentally bump it when you’re in the maintenance room (or wherever your water heater is), or maybe your child bumped it while playing in the areas. Your plumber might’ve forgotten to open the valve all the way, too. 

Either way, the fix is simple. All you need to do is open the shut-off valve completely to allow an adequate flow of water through the pipe. 

Sediment Buildup

Calcium and other minerals can build up in your water heater as a result of hard water in your home. Eventually, these deposits build up in pipes leading from the tank and settle at the bottom of the tank as sediment. Sediment buildup can lead to water flow restrictions, causing low water pressure throughout your home. 

In many cases, the problem occurs slowly over time, eventually restricting and lowering the water pressure until you notice a difference. However, while sediment buildup can affect the water pressure in your home, it can also lead to other issues with the heater’s efficiency. 

If this is the problem, you’ll need to flush the system to remove sediment buildup. Since water heaters are highly pressurized, this job is best left to a professional. You’ll need to have the system flushed periodically to prevent buildup. 

Alternatively, you can invest in a water softener to solve your hard water issues throughout your home. However, this can be costly, so it might not be feasible in some situations. 

Pipe Problems

In some scenarios, water heaters are installed with a series of pipes with numerous twists and turns. These abrupt changes in direction can lower the amount of water pressure the pipes can deliver. 

This issue is common in homes where the basement layout doesn’t easily accommodate a water heater, requiring unusual placement to make it work. The solution problem can range in difficulty, as sometimes the problem is a simple fix, while a skilled plumber is necessary in other cases. 

In some cases, there isn’t a fix for the layout of your home and its lack of compatibility with a water heater, so you might want to consider a tankless water heater

Common Causes Of Low Water Pressure

Your water heater might not be the culprit causing low water pressure throughout your home. In some scenarios, the issue lies somewhere else in your home. Here are a few common causes of low water pressure (that aren’t associated with your water heater). 

Faulty Pressure Regulator

Pressure regulators are an essential part of your water system. They’re designed to maintain consistent water pressure throughout the entire water system. Generally, the manufacturer sets the regulator to around 45-60 psi, so adjustments aren’t necessary. 

However, sometimes you might need to adjust the regulator to improve water pressure issues. If the device is faulty, you’ll need to fix or replace the entire thing, which requires the assistance of a licensed plumber. 

Partially Closed Shut-Off Valve

As mentioned earlier, a partially closed shut-off valve can lead to reduced water pressure. However, instead of the shut-off valve on the water heater, this valve controls the flow throughout your entire home. 

This can occur after completing a plumbing project that requires turning off the water at the water main. Simply check the main shut-off valve (usually outside where the water system enters your home by the water meter) and ensure it’s completely open.

Plumbing Leaks

When your plumbing system isn’t receiving the water it needs, your home may experience low water pressure. Leaks and holes throughout your piping system allow moisture to escape as it passes. This can lead to reduced water pressure in certain areas of your home and severe water damage in the leak area. 


Oxidation within the pipe walls can restrict the path for the water to flow. While this problem isn’t a concern in certain plumbing materials (PEX, PVC, etc.), it can become an issue with older galvanized pipes. Corrosion can build up on the walls of the pipe, causing issues with water pressure, among other problems. 

Debris In Plumbing

Debris can build up in the pipes over time, causing reduced water pressure. Since there’s less space for the water to travel through due to the smaller water line, you may notice lower water pressure as the debris slowly builds up. 

Things like dirt, sand, food particles, solidified oil and grease, and foreign objects can create blockages, eventually leading to this issue. 

Water Supplier Problems

Sometimes, the problem goes beyond your home. For example, your neighbors nearby might be experiencing the same problem. Check with your neighbors to see if they’re noticing low water pressure in their homes as well. 

If they are, the problem may lie with the supplier or municipal water supply. Call your water supply company to check if there are ongoing issues and what the company is doing to fix them.

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