Curious to Know How Long Does It Take to Fill a 40-gallon Water Heater?

Pipeline in boiler room, independent heating system

Not everyone likes their bath water, cold. I, for instance, have times where I wake up and choose between either hot or cold. There are a lot of things that affect these choices, which include the weather or mood. Cold bath water is effortless to accomplish, but heating water takes a lot of effort to do so.

But before anything else, there are still some questions that need answers. For instance, “how long does it take to fill a hot water heater,” and “what type of heater should I get?” are some things we need to solve first.

What You’ll Get in This Tutorial

builder or plumber working indoors

If hot water heaters will serve one basic function, that is, to warm your bath water, then you’ll know it is a good product, right? But buying a product to depend on consistently is something worth giving much of my time.

As I sat down to list the features I would love my hot water heater to have, there’s something rather trivial to some, but for me, is an equally important thing to know, as much as performance and quality are concerned. How long does it take to fill a hot water heater? Here is a guide on electric tankless water heater reviews as we uncover some tips and tricks in choosing what will keep the biggest tank filled easily with heated water.

Look, during winter days, a hot bath is something I look forward to. So is every member of my family. Knowing how much time it takes for my 40-gallon water reservoir to be heated up is significant.

And knowing how long does it take to fill a hot water heater will not just benefit me with a hot bath every time I need it, but will also ensure that my electricity bill won’t shoot up too high during those times that the demand is high. And most importantly, I should know how to fill the hot water heater correctly and safely.

In this tutorial, I will discuss all you need to know about hot water heater filling performance, how-to, and safety:

  • How long does it take to fill a hot water heater?
  • Choosing the right hot water heater
  • How to get started on filling and using the hot water heater

Let’s get things moving now.

  • How long does it take to fill a hot water heater?

Refilling a 40-gallon water heater won’t take too much time if water pressure is high. Usually, it would only take 10-15 minutes to have the water ready for heating. It is not always required to fill it immediately, but it’s efficient to do so to start the water heating process.

The water heating process usually takes around 2-3 hours, depending on the type of water heater you have at home.

  • The Best Type of Water Heater for You

There are two main types of water heater widely available in the market. But before deciding what to buy, be sure to know how long does it take to fill a 40 gallon water heater. One uses natural gas, and the other uses electricity.

For a big family, it is recommended to get an electric powered heater to utilize the storage it offers.

For frequent use, we think that natural gas water heaters are best.

Let’s Get Started

Filling the Water Heater

Now let’s jump into the real deal.

We highly suggest that you proceed in this part if you have completely understood how long does it take to fill a hot water heater.

Filling a tank of water might sound easy for anyone, right? But water heater tanks are special snowflakes that require effort and knowledge to supply. It is also recommended to follow these steps to ensure safety.

Step 1: Turn off any electrical power connected to the heater.

It’s common sense, just like how you should be knowing how long does it take to fill a hot water heater.  But it seems like a lot of people forget this first and most crucial step. Water is a conductor of electricity, and it would be very harmful if anyone touches hot water infused with electricity. It is also suggested never to skip this step to save power and therefore cut cost for power consumption. For natural gas users, turning off the gas valve is enough.

Step 2: Drain the remaining water.

Close the cold-water valve to prepare for draining. Review and ask yourself how long does it take to fill a hot water heater before proceeding. Connect the hose to a drainage valve to drain the water to either outdoors or the drain. Draining the remaining water is very important to prevent any complications with the water supply and the water heater itself. Flushing the remaining water every time you use the item is also a good process and would improve the longevity of the device.

After doing so, close the drainage valve and carefully place the hose on its original place.

Step 3: Fill the heater with water from the cold-water valve.

Open the hot water faucet once above steps are done, and you are half-way to completion. At this point, asking ourselves how long does it take to fill a hot water heater has helped us so much.

Moving on, you may now start the water filling process. This one usually needs a waiting depending on the household’s available water pressure. Water needs to be clean to ensure the safety of the whole household. Be sure to run some checks and tests firsts before proceeding to fill everything. Unclean, filled water is waste, energy, and resource-wise. If it starts to have a steady and constant flow, quickly shut down the tap.

Step 4: Restore the power.

Now that the water heater has full water, it’s time to restore the electricity. Quickly check if our estimation is correct on how long does it take to fill a 40-gallon water heater. Plug-in all essential wires and plugs to start the restoration process. As aforementioned, it roughly takes 2-3 hours to heat the whole device, so it’s better for you to have something to do while waiting.

On the other hand, you can also do this whole process before going to sleep. In that way, you will have a hot water one you wake up. I do this a lot since I take a bath afterwards. I eat my breakfast. I don’t want to wait for several hours to have my water heater painstakingly. That’s why I’m always telling everyone to have their water pre-heated before they even think of using it.

Step 5: Check the drainage valve.

A lot of people, including me, forget a lot of things and this even includes our favorite question, “how long does it take to fill a hot water heater,” that’s why just like what I’m doing, I’m telling you guys out there to re-check your drainage valve once you restore power. You can also do this before connecting the electronic paraphernalia to ensure that everything runs smoothly.

It is also essential to have your drainage valve tightened to prevent leaks and other problems. To make sure that the lid is good to go, you can use several tools like, for instance, a wrench to aid for the tightening process. While you’re on it, why not check everything after all? It doesn’t take up a lot of your time, and it would save more time of yours if you prevent problems.


Knowing how long does it take to fill a 40-gallon water heater may not sound like the most challenging task, but it would be one if you don’t know what you’re doing. We’re pretty sure that after this tutorial, you would be able to fill a water heater 100% safely. It’s essential to take note the safety measures we indicated since a lot of people tend to forget them. We highly suggest making a checklist every time you do this task. I do this one too! So, there’s nothing to get ashamed about it.

The figures and durations we mentioned above, including the answers to questions like “how long does it take to fill a hot water heater?” are only pure, and all of them can change if some variables also change. That’s why researching and experience are significant to fully know what your water heater type or model can do. We suggest to monitor your water heater and observe its performance for a long time.

We’re highly sure that a water heater is a good investment. But before anything else, be sure to know the essentials, including how long does it take to fill a hot water heater. A lot of people are also giving their testimonies with it, so be sure to check them online. It can run for countless of times, and it is also very durable, and would probably last for some years before yearning for maintenance or replacement.

Well, I think that’s a wrap! We hope that you find this tutorial helpful and if you did so, don’t forget to share it to anyone interested in water heaters too! We really hope you learned a lot of things, including how long does it take to fill a hot water heater.

Wanna learn some more?

Recent Posts

Legal Disclaimer is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Additionally, also participates in other affiliate and advertising programs, such as AdSense, ShareASale, Awin, Etsy, and CJ among others, and is compensated for referring traffic and business to them.