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How to Fix Low Water Pressure After Water Heater Replacement?

By Albert G. Croley
2K views 2 mins read

I never thought I was going to say this, but this winter was literally brutal.

But the urge to clean myself up wasn’t going anywhere.

So, I went to hit the shower, expecting my new heater to show me its magic.

But the water came out of the shower like someone was squeezing its throat.

Clearly, I had no other choice but to contact a professional, as I had no idea about how to fix low water pressure after water heater replacement.

I didn’t know that was going to make me regret it.

No, he did his job perfectly and didn’t forget to take in some solid cash too.

The regret part came in when I saw that knowing that basic thing could’ve saved me some thick bucks.

So, I made up my mind to know it all, and this guide is going to transfer it to you too. Keep reading if you’re planning to deal with that kind of troubleshooting all by yourself.

Key Takeaways:
Small leaks on pipes, clogged aerators, and faucet screens are things you can fix on your own. The remaining ones might need professional attention.
To prevent it from happening, inspect the plumbing regularly, get the right-sized heater, and handle valves carefully.

How to Fix Low Water Pressure After Water Heater Replacement: Reasons & Fixes

There are a ton of reasons why you can experience low water pressure.

But how to fix low water pressure after water heater replacement, specifically?

Well, here are the major reasons for that happening and also how to fix them in the first place:

Reason 1: Sediment and Debris

This is probably the most common cause you’ll see out there that causes low water pressure. And yes, this can happen after installing your new heater too.

Sediment and Debris
Sediment and Debris

The credit goes to the rust, debris, and minerals that restrict water flow by piling up. This mostly happens on parts like the faucet aerator and shower head. Not even internal faucet parts are free of this issue.


  • Check the faucet aerators and showerheads to see if there’s any visible debris. If you see the mesh of the aerator catching debris, clean it up gently with a soft brush.
  • If the aerator wasn’t causing the issue, check out the internal faucet parts. There’s a chance that sediment within the faucet is keeping the water pressure low. So, disassemble the parts and clean the components.
  • Find out the inlet screen if you have a tankless model. Give it a proper cleaning to get rid of any trapped sediment there.
  • Sometimes the built-up sediment goes beyond cleaning. In such cases, replace the old fixtures with new ones.

Reason 2: Low Pressure From Water Supply

It’s not always the fault of your heater or water pipes. Sometimes your city’s water supply can be the cause of low pressure too. This happens mostly when there’s an increased demand for water, issues with the main line, or issues with booster pumps.

Low Pressure From Water Supply
Low Pressure From Water Supply

To be sure about this particular issue, check if the whole house’s water pipes are getting low pressure. Plus, ask your neighbors if they’re facing the same issue or what.


  • Wait it out. Usually, this type of issue gets resolved within a short period of time.
  • Contact the water company in the first place. From their answers, you’ll understand what to do next.
  • If the issue keeps popping up regularly, consider installing a pressure booster pump to get adequate water pressure. For this, you’re going to need some professional help.

Reason 3: Leakage

It’s probably the water leaks that are stopping your plumbing setup from maintaining optimal water pressure. As leaks let water escape, the water pressure in the entire house can go down.


On top of that, they suck in air and create pockets that cause low pressure by blocking the water flow. Damp spots, mold around the water heater, and hot water pipes are the most common signs of leakage.


  • Identify the leak first. Look out for water stains and damp spots. If you’re not seeing any visible signs, try to listen to the hissing or gurgling noises.
  • Once you find the leak’s location, get your tools, including patching materials, wrenches, and pipe cement.
  • Find the shut-off valve for that leaked pipe and turn it off.
  • Use your patching materials on the leak. Tighten the loose connection if there’s any. Once you fix the problem, turn the water on again.

Reason 4: Corroded Pipes

You already know how minerals narrow a pipe’s diameter by building up inside it. Clearly, that’s enough to create a low-pressure problem. But when you’re installing a new heater, that can potentially trigger the corrosion issue, though not directly.

This basically happens due to the increased water dislodging the current corrosion flakes. As a result, the clogging issue takes place.

Plus, the heater changes the pressure level, which brings out the hidden corrosion. So, along with the low pressure, if you see uneven water flow and rusty or discolored water, probably the corrosion issue has kicked in.


First off, check out if it’s minor corrosion or major. If it’s a minor one, call in a plumber and ask him to fix the issue with the internal pipe lining, if possible. This will save you the cost of a complete replacement and fix the issue of water pressure in your home.

But if the case is severe, you’ve got no other choice but to replace the corroded pipes. Make sure you’re asking for a proper professional, whether it’s a matter of repairing or replacing.

Reason 5: Clogged Aerators & Faucet Screens

Clogged faucet screens and aerators also make water pressure low after installing a heater. The continuous flow of hot and cold water makes them catch debris later on, leading to reduced water pressure.

Corroded Pipes
Corroded Pipes

It’s mostly the mesh screen of the faucet tip that gathers minerals and debris over time. So, if you’re seeing weak water flow or the water stops running completely, unscrew the faucet and check what went wrong.


  • Unscrew the aerators first. Rotating it counterclockwise should be enough for that. Try using pliers if it’s stuck. This will keep the threads from getting damaged.
  • Clean up the screen with warm water and a toothbrush. Gently scrub the screen to get rid of the visible debris. But if the clogs are acting stubborn, soak them in white vinegar for the next 30 minutes.

Reason 6: PRV Issue

Though rare, pressure relief valve (PRV) issues can also be one of the causes of low water pressure. As a safety feature, the prime function of PRV is to release excessive pressure to protect the tank from ruptures.

PRV Issue
PRV Issue

But if it’s somehow adjusted wrongly while installing your heater, it can restrict water flow so much that the pressure can go down.


Adjust the PRV if possible. If your one has an adjustment screw, check the water heater manual and adjust it as instructed. But make sure you’re sure you have proper knowledge about this.

Otherwise, it’s better to get professional help, as overtightening will restrict the flow more. But if the PRV itself is faulty, replace it with a licensed plumber.

When Should You Call a Professional?

If you’re thinking about how to fix low water pressure after a water heater replacement without a plumbing professional, that’s great!

But that’s not always going to happen. Hence, the smart call is to know when you need to call for one:

Failed DIY Fixes

You’ve probably done everything you could, including checking for leaks and cleaning the faucet screens and aerators. But if the flow of water and pressure are still low, it’s better to let a professional handle this.

Pipe Issues

When you suspect serious pipe issues like rusty water or a continuous pressure drop, you should call a professional to check it out. It’s probably happening due to pipe corrosion or leaks.

Pressure Relief Valve Issue

Sometimes a faulty pressure relief valve can be the culprit too, leading to leaks and low pressure. In such cases, you need a professional for proper diagnosis and repair.

Complicated Leaks

You can’t see every leak in your pipe setup, especially when it’s in a concealed location. This is where you will need the professionals.

They come with the required tools and expertise to tackle every kind of situation.

Preventative Measures and Best Practices

Prevention is always better than cure. So, rather than doing the repair, try preventing it in the first place. All you have to do is the following:

Do a Plumbing Inspection

When it comes to old plumbing, it might come up with a few potential issues.

So, the best thing you can do before installing a new water heater is to ask a professional plumber to inspect your pipes. This will help you detect leaks, blockages, or corrosion, if there are any.

Get the Right Size Heater

Make sure your new heater is the perfect size for your hot water needs. After all, an oversized heater will do nothing but put extra strain on your plumbing system.

Handle the Valves Carefully

After installing the heater, check to see if both the cold and hot water shut-off valves are fully opened. Otherwise, the water flow will be restricted.

Lower the Disruption

You can’t always skip some displacement of sediment while installing your heater. But if you can carefully handle and flush the system, it shouldn’t be a problem to minimize the amount of debris released into your pipes.

Clean the Aerator Regularly

When you’re using hard water, make sure to keep the faucet aerators and showerheads clean on a regular basis. This will help you ensure good water flow while preventing mineral buildup at the same time.

Using Water Softener

If you’re not a fan of hard water, try using a water softener. This should lower the corrosion and sediment buildup. Clearly, that will take down the risk of water pressure issues later.

Final Words

I guess now you know how to fix low water pressure after water heater replacement.

At least you’re not clueless anymore about what’s going on with your new water heater. Here, I’ve tried to tell you about the potential causes and the fixes. And also, why and when you’re going to need a plumbing professional in the first place.

But the best thing you can do is prevent it from happening. So, I’ve added some tips on that too. Just make sure you follow them properly unless you want to irritate yourself with poor flow under the shower like me.

Frequently Asked Questions (FAQs)

How long to run water after a new water heater?

Once you’re done installing a new tankless heater, run hot water for the next 5–10 minutes. But if the heater is tank-style, keep it running for 20–30 minutes.

Does water heater temperature affect pressure?

Yes, a water heater can affect pressure. In fact, when the water gets heated, it expands. So, this raises the pressure within the tank. If the temperature goes too high (above 120°F), it can create issues with water pressure and potentially lead to leaks.

Can a water heater cause air in pipes?

Yes, it can. Basically, the tank’s internal rust creates hydrogen gas. Once it mixes with water, it turns into air bubbles. Plus, a faulty pressure valve and rapid filling can also be potential causes of air in pipes.

How do I check my hot water pressure?

Get a pressure gauge first. Attach the gauge to the faucet adapter after turning off the water line. Now fully open the hot water faucet. Check the gauge, and if it’s 40–60 psi, count it ideal. But if it’s below 30, it indicates low water pressure.

Can a water meter get clogged?

Though it’s a rare case, water meters can also get clogged. It can happen due to mineral buildup and debris in the meter strainer.

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