Keeping tea in a stainless steel thermos, is it OK and how long?

I would try the tea fresh from the carafe. If it’s taste horrible already, then it could be the tea, the water, the carafe, or the way you make your tea. If your tea is fine from the carafe, then work down your list to find the culprit.

I tried this and it tasted very similar to the tea steeped in my mug. I’m beginning to think it’s a combination of boiling hot tea left in the vacuum flask for a long time. Tonight I made some tea in a large glass measuring cup and then let it cool for 5 mins. It was hot but not boiling and rather drinkable. I put it in the flask and will report on it’s taste tomorrow.

I can’t imagine it’s caused by the vacuum flask itself. After all that thing was made for this purpose, isn’t it? At work, we make tea in a similar way and have it for the entire workday, so that can get 7 hours old as well towards the end of the day. Cools a bit, but doesn’t otherwise change flavour or smell.

What else have you had in it though?

Does the carafe itself smell bad? Does it need cleaning? (What have you cleaned it with? Any risk of residue?)

Is there any difference between when you make it in the morning as opposed to the night before?

So I made my tea around midnight last night and tried it this morning around 9 am. It tasted a bit better than the last time when I put almost boiling hot tea in it, but it still smells the same. It’s a really gross smell, which smells something like Spaghetti-O’s. The only connection I can make is both my tea and Spaghetti-O’s are stored in metal containers. I will store my tea in glass out on the counter next time to see how it tastes in the morning. Maybe it’s the tea?

I have used dish soap and hot water and shook it vigorously. I’ll try baking soda and vinegar and see if that fixes it. Just mix them together?

I use several steel vacuum tumblers and something to check is the seal on the top lid, usually has a plastic ring of some sort on those things, and you literally have to scrub it in between uses sometimes if you let the tea sit in the thermos for a long period of time.
In addition to rinsing with natural cleaners like vinegar and/or baking soda, you have to be sure that you’re drying things thoroughly as well, or all the rinsing in the world won’t solve the problem. Each night I pop open the seal and run hot water through, but I also take a paper towel and wipe the plastic seal rings – there’s usually dust/coloring that rubs off even after the rinse, so if I weren’t being diligent with the drying, it would get funky very fast.

Well I ran both through the dish washer, the plastic cap doesn’t smell, but the grey rubber o-ring still does. Can you soak rubber in vinegar?

Try Klean Kanteen insulated water bottles! They’re good for hot and cold water, and they’re entirely stainless steel- no annoying rubber rings. I’ve had mine for two years, and never any problems- I’ve put both hot tea and water in it (although you should refrain from putting sugar/milk/anything else in it, which makes for funky smells :/)

Same smell for me. I got a Thermos brand stainless steel vacuum bottle 1L with black cap n white rubber gasket. The smell definitely comes from cap in contact with boiling water
Any probable fix to this issue? When pouring boiling water to CUP (inner is plastic / outer is stainless) smell is intensified. How do we clean plastic parts? Factory defect?

i came across this site while searching for information on my vaccum flask. I like stainless steel so of course my flasks, all four are from stainless steel. I noticed varying levels of odour when i open a the caps but just thought it was the steel reacting with the hot liquid.

Just yesterday i accidentally dropped one of my flask and the bottom came off. What i believed is the heating element or what keeps the heat, is covered with a hard red resin like material and it smells horrible.

I do believe this is what is causing the odour in my flask. Thr hotter the liquid the stronger the odour. This was quite frightening as i dont know what this resin like thing is or if it dangerous to my health.