hot tub heating slowly

Hot tub owners all dread having to drain and refill their hot tubs. But, unfortunately, heating up a freshly-filled hot tub can take several hours, leaving many hot tub owners to wonder, “how can I make my hot tub heat up faster?”

Here’s what I know from owning 4 of them for over 15+ years:

To heat a hot tub faster, turn the jets and water features on, ensuring the water circulates through the entire tub eliminating cold pockets. And no matter the outside temperature, keep the lid securely closed. This will trap the heat and keep it in the water instead of allowing it to evaporate.

But that’s just a quick answer with 2 of the solutions to a slow-heating hot tub.

In this article, we’ll dive into all the things you can do to heat it up faster, including the one tip I’ll share that most hot tub owners never even think of.

Let’s get going!

Tuesday Tips — When heating or adding chemicals to your hot tub, be sure to turn off the air valves. This will allow the hot tub to heat up quickly and the chemicals will mix with the water faster.#westrockpools #hottub #spa #tuesdaytips #hottubmaintenance pic.twitter.com/In3FyaDnqv

— Westrock Pool & Spa (@Westrockpools50) January 23, 2018

How long does a hot tub take to heat up?

The average hot tub takes 4-8 hours to heat up entirely and heats between 3 and 6 degrees per hour. The water temperature from the hose and the power rating on the heater are the two biggest factors in the total heat time.

In a recent article, I went into some detail discussing the factors that affect the length of time it takes a hot tub to reach its optimum temperature, including the one thing I’m sure you’re probably doing right now that is slowing it down.

Just click on the link to read it here on my website.

One of the most significant factors that affect total heat time is the amount of water in the tub. An average four to six-person tub will contain up to 300 gallons of water, so that’s a lot to heat up to 100°F from cold.

You may be tempted to use hot water from your home but beware.

The temperature of the water coming out of your faucet can be as high as 130°. The maximum running temperature of your hot tub is usually set at 104° F (40° C).

So the higher temperature could damage the pipework and equipment, not to mention the shell, and you certainly would not be able to get in.

Ideally, to avoid any damage, use the water from your garden hose and let the heater, pump and jets do their job. In the summertime, the hose water temp is likely to be around 75° to 80° anyway.

We recently visited a hot tub where the PH was very high, causing the heating element to fail, so here are some helpful tips on keeping on top of your levels. #hottubtips #spafix #staycation #spafixtoptips pic.twitter.com/lfkWtMgIOB

— Spafix (@SpafixServices) October 30, 2020

Why is my hot tub heating up slowly?

A hot tub that is heating slower than normal may have a dirty filter, which slows down the flow of water into the heater. Additionally, the intake valves on the floor of the hot tub may be clogged.

So the first step should be to remove the filters and clean them thoroughly with a garden hose or kitchen sink sprayer. Unless you see debris in the water, assuming you’ve just refilled it, you’re also OK just removing the filters during the heating process.

There are actually several factors that affect the speed at which a hot tub heats up:

• The temperature of the water in the tub to begin with (avg range is 60-75 degrees F)
• The outside air temperature
• The amount of water to be heated
• The size of your heater
  
  

If you have a plug-n-play hot tub, it most likely runs off 110v, and this limits the size of your heater to around 1 to 1.2kW.

This will warm the water up much slower than a 4 or 6kW heater, which you find on most regular tubs. Besides, you cannot run the pump and heater simultaneously on most plug-n-play hot tubs.

Some plug-n-play hot tubs can be converted to 240v, which means the heater can be upgraded to a 2kW model. It also means you can run the heater while using it with the jets on full, but this will require modifications to your control box that you’ll need an electrician for.

You will need a 240v outlet on a dedicated 40amp circuit to hard-wire the tub into via a disconnect box, and I explained how to do this in a recent article. Click the link to read it on my site.

A 2kW heater will heat the water to 100° twice as quickly as a 1kW heater, so if speed is a factor, this might be worth considering.

Hot tub got warm much quicker than I expected so I’ll be here until it freezes over again. pic.twitter.com/32H5r9sILk

— Juliet Frost ❄️ (@polarbearjuliet) December 7, 2020

How long does it take a hot tub to heat up 5 degrees?

An hour to an hour and a half is how long it will take the average 200v hot tub to heat up by 5 degrees. A 4kW heater will raise the water temperature in a hot tub by 3° to 6° per hour. But a plug-in hot tub may take as much as 4 hours to go up 5 degrees.

The amount of water in your hot tub will also affect the warm-up time. These figures are based on an average 250 – 300 gallon hot tub. Larger tubs will take longer.

This is why it is a good idea to leave your hot tub running all the time—even in standby mode, the temperature will only drop by around 10 degrees, so the heater can get you back up to 100° in just a couple of hours.

The optimum temperature for a comfortable soak is between 98° and 104° F (36.6° to 40° C). In warmer weather, you could probably get away with a bit less.

So, setting your temperature at around 96° could chop 2 hours off the warm-up time.

I discussed using hot water to fill your tub in a recent article, which you might want to read before going any further. I know people who run a hose from their hot water heater. And even a few that get tempted to boil water on the stove in large containers to speed up the process.

But make sure you read my article before trying either of those.

Tip: Sometimes, a hot tub or spa heating problem is as simple as a faulty heating element. pic.twitter.com/YUewAjaELB

— Unlimited Spa (@UnlimitedSpaSVC) April 4, 2017

How to heat up an inflatable hot tub faster

To heat an inflatable hot tub faster, make sure the insulated ground cloth is under the hot tub, and the inflatable bladder that floats on the water is present and fully inflated. Then, ensure the cover is on and latched.

Unfortunately, there is not much else that can be done to heat an inflatable hot tub faster.

Inflatable hot tubs are a great introduction to the world of hot-tubbing or for those who only want the occasional soak in the summertime. The one big downside is that they don’t hold the heat in very well.

This is because the walls are made up of two skins of vinyl and around 8” of air, and the covers—if you get one with your tub—are not usually very well insulated.

With the small heaters used by inflatables (typically a 1 to 1.2kW heater), they rarely heat faster than 2 degrees per hour, and if the air temperature is at or below 40 degrees F, expect to only get 1 degree per hour.

If the water from your hose is 70 degrees F and you have it set to 100 degrees F, that means it will take 15 hours to fully heat if the air temp is over 40.

I will say that when I first got my Intex inflatable hot tub, it was lower than 40° F (4.4° C) and it took about 24 hours to heat up to 98° F. So patience is key if it’s cold where you live.

I’ve had enough of my kids today. It is cold and they can’t play outside, homework is behind a screen, markets are all over, and my work just keeps piling up. Cleaned the hot tub. Does pouring boiling hot water in make it heat up faster? #aksingformyself #ineedmultipledrinks pic.twitter.com/7foc2b0ht9

— Maaike (@BirnamPork) April 7, 2020

Does leaving the cover on heat a hot tub faster?

Always leave the cover on a hot tub when heating the water. The cover will trap the heat and cause it to get recirculated back into the water rather than evaporating into the air. Even if the air temperature is at or above 100 degrees F the hot tub will still heat faster with the cover on.

The water in your hot tub is passed through a heater, so the warmer the water as it passes through, the quicker it heats up to its optimum temperature of around 100°F.

A well-insulated and well-fitted cover will also keep the heat in, so your heater doesn’t have to work so hard to keep the water at a constant temperature.

It is always recommended to leave your hot tub running in between soaking, as this keeps the water warm, and it is a lot quicker to heat it by 5° than it is 35°, and uses less energy too.

Leaving the jets running while the water is heating up will also quicken the process. This agitates the water and makes sure there are no pockets of cooler water in the pipes or the corners of your tub.

A word of warning, do not turn on the heater or the jets until the water level is above the highest jet. Doing so could damage the plumbing and equipment.

Did I cover all you wanted to know about making your hot tub heat up faster?

Waiting for your hot tub to heat up can be very frustrating, particularly when you just got in from work and you want a long, relaxing soak. But there are ways you can speed things up.

First of all, don’t switch off or unplug your hot tub after every use—if you allow the temperature to drop by 25°, it can take anything from 5 to 20 hours to get back up to 100°, depending on the size of your heater.

Secondly, make sure you have a well-insulated tight-fitting cover. If you can, add extra insulation to the walls. The more heat you keep in, the less time and energy required to reach a comfortable temperature.

If there is anything I missed, just drop me a line—I am always happy to help, and don’t forget to check out those links to associated articles here on my website.