Hydro Flasks are meant to hold ice cold drinks for 24+ hours and apparently they aren't meant to sweat. I've noticed some sweating on mine around the top and I know other people have entire Hydro Flasks that sweat.
So I wanted to work out why is my Hydro Flask sweat and what should I do if it is?
I ran some of my own experiments with my Hydro Flasks and some other products and did a bunch of research into why your Hydro Flask might be sweating and here's what I found:
Some minor sweating around the top of your Hydro Flask is completely normal as this part has the least insulation. If your entire Hydro Flask is sweating chances are the vacuum insulation has lost it's seal and is broken. This is covered under Hydro Flask's lifetime warranty.
In this article we'll have a look at the different reasons why your Hydro Flask might be sweating so you can work out if it's within the normal scope of the product or if you have some issues.
I'll also show you how to check whether or not your vacuum insulation is broken if you think that your Hydro Flask is sweating more than it should.
Reasons Your Hydro Flask is Sweating
There are a few different reasons why your Hydro Flask may be sweating:
Loss of Vacuum Insulation
The most likely cause of your Hydro Flask bottle (or tumbler) sweating is a loss of the vacuum sealed insulation.
See Hydro Flasks are made of double walled stainless steel with a vacuum in between. The vacuum is actually what gives the cup it's amazing insulating ability and stops the Hydro Flask from sweating even when there is iced water inside.
However, sometimes the vacuum seal can break which leads the vacuum to fill up with air. Heat can transfer through air much easier than through a vacuum so when this happens heat (or cold) can move from the inside of the bottle to the outside.
When you have icy cold water inside your Hydro Flask and the vacuum seal is filled with air the ice in your bottle will cool down the outside of your Hydro Flask making it cold to touch.
Moisture in the air will then condense into water droplets on your Hydro Flask and that' what we call “sweating”.
So if your entire Hydro Flask bottle is sweating all over, and it isn't just happening on the rim near the top of the bottle, then your insulation is likely broken.
There are a few tests described below to confirm whether or not your Hydro Flask is actually broken but if it is you should get in contact with Hydro Flask for a replacement.
Sweating Around The Rim Is Normal
The neck of your Hydro Flask is the place where the inner and outer wall meets. This is the area where there is little to no vacuum insulation.
This means that the coldness inside your bottle can transfer from the inside to the outside at this point.
The cool metal then condenses the warmer outside air and water droplets start to form on the neck of your Hydro Flask.
The neck of your Yeti bottle or cup is where the inner and outer walls meet and also the area with the least vacuum insulation.
This means that heat and cold can more easily pass through this section and the iced cold drink inside your Yeti can cool the outside part of the metal.
The cool metal then condenses the warm outside air and water droplets form on your bottle or cup.
If only the top/neck of your Hydro Flask is sweating and not the body then this is completely normal and isn't cause for concern. It's also generally not enough sweating to cause any real issues.
I also found this to be the case on other brands also. In my article on do Hydro Flasks sweat I also discovered that they have a tendency to sweat towards the top of the bottle just like the Yeti bottle.
This Reddit user had issues with the neck of their Yeti sweating and contacted Yeti about it and here's what they said:
So I contacted yeti and condensation or “sweating” around the neck area is normal. The neck is the thinnest part of the bottle and is not part of the double walled and vacuum sealed portion. If the sweating was occurring around the body or anywhere below the neck, then that would indicate a vacuum seal issue and would be covered under the 5 year warranty! So you’ve got yourself an “A-OK” Rambler!
Been In The Fridge/Freezer
If you've placed your Hydro Flask bottle in the fridge or the freezer then the outside of the bottle will become cold.
When you take it out of the fridge or freezer the stainless steel can start to condense the warmer outside air and cause sweating all over your bottle.
However, this is different from sweating caused by broken insulation.
Sweating caused by the fridge/freeze will be short lived. It'll happen initially as you take it out but then the outside of your bottle will quickly warm up to room temperature and it will stop.
This sweating can also happen if you're taking your Hydro Flask from the cold outside and bringing it inside where it's much warmer. This is more likely to happen in winter compared to summer.
Why Do Regular Cups Sweat and Why Aren't Hydro Flasks Meant To Sweat?
Regular cups sweats due to condensation. You probably learned about this in school but if you've forgotten how it works that totally fine. I forgot too and had to look it up.
The reason non-insulated cups sweat is that air is full of water moisture in the form of gas. When this water moisture in the air comes into contact with the cold surface of your drink bottle or cup it turns the gas into a liquid and sticks to your bottle in the form of water droplets.
It's kind of like your cup or bottle is acting as a fridge and turning the warm gas into liquid.
Without some sort of insulation when you put a cold drink in a bottle the outside will also get cold causing condensation and sweating to happen.
However, with double wall vacuum insulated bottles like Hydro Flask the vacuum stops heat transfer.
This means the cold from your drink can't get through from the inside of your bottle to the outside. It can't cool down the outside of the bottle because there is a vacuum in the way.
This means the outside of the bottle stays at room temperature and condensation doesn't happen.
How To Test If Your Hydro Flask Has Lost It's Insulation
Before getting in contact with Hydro Flask about your bottle sweating you might want to first double check whether or not your bottle has lost it's insulation or if something else has happened.
There are a few easy ways to check whether or not your Hydro Flask's insulation is broken.
Fill it with boiling water
Boil some water and pour it into your Hydro Flask filling it to the top. Leave for a couple of minutes.
Now check the temperature on the outside of your Hydro Flask bottle.
If it's warm or hot to touch then your insulation is likely broken. If it still feels like it's a room temperature then your insulation is likely completely fine.
See if it floats
This is a bit of a random test but it works because Hydro Flasks actually sink when filled with water. This is because the vacuum ha no bouyancy.
However, if your insulation is actually broken then the inside of your Hydro Flask will be filled with air, which IS buoyant. This will cause your Hydro Flask to float.
Fill up a sink or a bath with water and take the lid off your Hydro Flask. Completely submerge it in water with the mouth of the bottle point up to ensure all air bubbles escape and the bottle completely fills up with water.
Now let go and see if it floats or sinks.
If it floats your insulation is likely broken, if it sinks it's likely still fine.
Test against other Hydro Flasks or insulated cups/bottles
If you have another Hydro Flask lying around (or if your friends or family have one) then do a side by side test with boiling water.
See which one gets colder faster.
To speed up the test put both bottles in the fridge with their lids on. But it's probably best not to put your Hydro Flask in the freezer in case you forget about it.
If you Hydro Flask performs significantly worse than another similar sized vacuum insulated bottle it's likely you have an issue with your insulation.
What Should I Do If My Hydro Flask Is Sweating?
If your Hydro Flask is sweating and you've checked that yes, the insulation is actually broken and has been compromised then you'll want to get in contact with Hydro Flask and let them know.
Hydro Flask have a limited lifetime warranty on their bottles and this covers the insulation failing (which is not completely uncommon).
They should be able to organise a replacement for you. You may need to send your bottle back to them first.
Alternatively if you don't want to go through that hassle or Hydro Flask refuse to replace your bottle then maybe you need to buy a new one.
Is Sweating Covered Under Hydro Flask's Warranty?
Hydro Flask bottles all come with a limited lifetime warranty against manufacturer defects.
While “sweating” is not talked about on their warranty page they do cover “Flasks that seem to have lost their insulating properties”.
The product needs to be purchased from an authorized dealer (learn more about how to spot a fake Hydro Flask) and you'll want to have your proof of purchase handy as they'll likely ask for this.
They also state:
YOU WILL BE REQUIRED TO SHIP YOUR WARRANTY PRODUCT BACK TO HYDRO FLASK FOR REVIEW PRIOR TO US SHIPPING YOU A WARRANTY REPLACEMENT PRODUCT.
But assuming your sweating Hydro Flask is covered under warranty you should get a replacement bottle free of charge.