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How Long Does It Take to Fill a Hot Tub?

By: Author Jeff Campbell

Posted on  - Last updated:

Categories Hot Tub Operational Tips

Hot tubs are great. However, it takes a while to fill them when you change the water. So I used to wonder, how long does it take to fill a hot tub?

The average 300 to 400-gallon hot tub will take around 90 minutes to 120 minutes to fill. But getting a garden hose with a larger than 3/4 opening on the filling end can speed that up. 

But that’s not the whole story. So let’s keep going.

The rest of this article will answer some essential questions about filling hot tubs:

  • Why some hot tubs take longer to fill than others
  • How long it takes to heat a hot tub with freshly filled water
  • The frequency you need to change the water in a hot tub
  • Should you turn the power off when filling a hot tub?

I even cover the 1 way you can drain your hot tub in less than 15 minutes without removing your siding!

How Long Does a Hot Tub Take to Fill Up?

While the average hot tub takes a couple of hours to fill up, no single number is accurate. Several factors will affect the amount of time it takes to fill up your hot tub. However, you’ll undoubtedly be able to use the tub the day that you set it up.

Below are a few factors that will impact how quickly your hot tub fills:

1. The size of the hose you’re using to fill it up

One of the main variables you must consider is the size of the hose that you’re using to fill the tub.

Some hoses have diameters of ½ of an inch, while others can be upwards of 1.5 inches in some instances. The standard size is usually ¾ of an inch, though.

2. The size of the hot tub

Hot tubs come in many different sizes. The average spa is about 300 gallons.

  • The average hot tub is 300 gallons
  • The smallest hot tubs are 150 gallons
  • The largest hot tubs are 700 gallons

Every hot tub tells you how many gallons you need to fill it up, so check your hot tub’s manual if you’re not sure. The larger the hot tub, the more time you’ll have to spend filling it up.

3. Water pressure

Your water pressure will have a significant impact on the time it takes to fill your hot tub. The higher the pressure, the quicker your hot tub will fill.

People who live out in the country and rely on well water sometimes get lower water pressure. In contrast, people who live in newer communities usually have higher water pressure.

Keep in mind that water pressure is also affected by the length and diameter of the hose you’re using. The smaller the opening of the hose, the higher the water pressure will be.

Not sure how often you should change your hot tub water?

In a recent article, I break down exactly how often that should happen. But I also cover how to do it quickly and easily!

I even tell you the 1 reason why it might be every 3 months for some people or every 6 months for others. Just click that link to read it on my site.

How Long Does It Take to Heat a Hot Tub With Freshly Changed Water?

The average hot tub takes anywhere from 3.5 to 8 hours to heat up.

Several key factors determine how long it takes to heat your hot tub. Keep in mind that your body temperature lowers the heat of the hot tub a bit, so don’t jump in until it’s at the temperature that you want.

I cover this in greater detail in a recent article (click to see it on my site).

I even cover some quick tips for speeding up the process so you don’t have to wait a whole day to take a plunge. So definitely click that link to get your water hotter faster!

But here are some factors that will affect the amount of time it takes to heat a hot tub with freshly changed water:

  • The weather and temperature. Rain, wind, and cold air can dramatically increase the amount of time it takes to heat a hot tub. Rain can also fill your hot tub with algae-causing phosphates, so try to cover the spa while it’s heating to retain as much warmth as much as possible.
  • The hot tub’s heater. There are a few different heater options out there, with 250K BTU and 150K BTU leading the pack. Bigger heaters use more power and will heat your hot tub much faster than a smaller, less powerful heater.
  • The size of the hot tub. A large body of water like a swimming pool will take a lot longer to heat than a hot tub. The same principle applies to hot tubs of varying sizes. You might find that a 600-gallon spa takes at least six hours, whereas a 300-gallon spa could heat up in only four to five hours on a sunny day – sometimes even less.

One reason you might need to drain a hot tub, and then refill it, is if you have a leak.

Hot tub leaks can be incredibly frustrating! They are hard to locate and where they are located if often hard to get to and work in.

Luckily, in a recent article, I break down every type of common hot tub leak AND how you can fix it yourself. In most cases, those fixes are quick, easy, and inexpensive too!

Just click that link to read it and bookmark it (trust me; you’ll need it eventually!)

How Often Do You Need to Change the Water in a Hot Tub?

If you don’t use your hot tub too often, you should change the water every three to four months. If you have several people using your hot tub every day, you should replace the water every one to two months.

Frequent changes are necessary because hot tubs are warm, which makes them ideal breeding grounds for bacteria.

Secondly, hot tubs are relatively small, which means they become contaminated much more quickly.

The other reason that you might have to change your spa water every few months is because of something known as TDS, or Total Dissolved Solids.

TDS occurs when too many solids enter a body of water; in this case, a hot tub.

When the water becomes too saturated, the solids can’t be absorbed. They become visible, and they also lower the effectiveness of chlorine, bromine, and other chemicals.

There are plenty of meters that you can use at home to check your TDS levels. If it’s too high, there’s no way to lower it other than a drain and refill process.

Some homeowners prefer to drain the tub halfway before refilling it to cut the TDS levels in half, which is an option if you notice that they’re rising too often.

However, a partial draining will still leave your hot tub contaminated, so it’s best to opt for a full drain whenever possible.

How do I empty the water in my hot tub before refilling?

With my last hot tub before the nicer, newer one we have now at our new house, I had to get out the cordless drill and remove the wood paneling.

Then I had to close one of the slice valves, remove the pipe, and point it away from the hot tub. Then and only then, could I start to drain it.

It was a pain in the you know what!

The hot tub we have now has plastic siding. With this one, I just take off 2 hand-screws on the corner and remove it to reveal a hose spigot.

Then I just attach a garden hose to the spigot and direct the hose away from the hot tub.

Your hot tub might be different from either of those. But most likely if it’s a newer tub, it will be like what I just described.

BUT, if you want to skip all that, do it the easy way, and get what I just got!

I got a submersible drain pump with a 25′ hose. No more siding to remove and no garden hoses to hook up.

Just drop this thing in your hot tub and see it drain in just minutes!

My hot tub takes an hour and a half to drain. But with this, I can drain it in 15 minutes!

It has great reviews on Amazon and comes with free shipping.

Just be aware, it has to be submerged under the water before it will power on. So don’t turn it on out of the water and think it’s broken.

There will, of course, be a little water left at the very bottom when it’s done, but that can easily be removed with a  wet-dry vac.

CLICK HERE to check the current prices on Amazon on the submersible drain pump.

Should I Turn the Power Off When Filling a Hot Tub?

You don’t need to and I never have.

After all, this thing is built around water. So if there’s an electrical issue, it will be there whether you’re filling it or not.

Now if your hose is likely to spray all over the place or pop out of the hot tub, there’s no harm in flipping the breaker to off.

Also, if the electrical line was not installed by a licensed electrician, it could be a good idea to turn it off.

As always, make sure your hands are dry before touching any live electrical equipment.

Typically hot tubs have a dedicated electrical panel on the side of the house located somewhere near the hot tub. Just lift the metal door up and flip the breaker off and you’ll be just fine.

Once you’ve filled the hot tub to the desired level, you can then proceed to plug it back in or turn the power back on.

Another bonus of turning it off is that when you’re filling a hot tub is that the jets should never run when the tub is dry. More modern tubs may have safeguards against this, but yours may not.

Running a pump without water can quickly strip the bearings inside of the pump, permanently damaging it.

So it’s your choice, but if you want to be extra cautious, go ahead and turn the power off.

Final Thoughts

In this article, we took a quick look at hot tubs refilling them. We explored how long it takes to fill them up. But we also looked at some of the reasons it might take longer.

Here are the takeaways from this article:

  • The average hot tub takes between 90 minutes and 120 minutes to fill up. The size of the hose, the size of the hot tub, and your water pressure will all affect the time needed.
  • It takes between three and a half hours and eight hours to heat a filled hot tub. The time depends on the size of the tub, the weather, and the strength of the heater.
  • If you’re using your hot tub infrequently, you should change the water every three to four months. If you use your hot tub daily, you should change it every one to two months. Changing your water is necessary to prevent bacterial growth.
  • It would be best if you turned the power off when filling up a hot tub. While it’s not strictly necessary, it’s best to be safe and avoid any risks.

Confused about hot tub chemicals?

Hot tub chemicals are confusing. How much should you add? Which ones should you buy, and are all of them really necessary?

I take ALL the confusion out of it in a recent article.

I not only get into exactly which chemicals you need but also the ones that are a waste of your hard-earned money.

Then I also examine which chemicals are best for sensitive skin and how to avoid the dreaded hot tub rash.

Just click the link to read that on my site.

As an Amazon Associate, I may earn a small commission from qualifying purchases if you click on Amazon from my site and choose to make a purchase. You can read my complete affiliate disclosure for more details.

Jeff Campbell
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