Thermos bottle in the dishwasher? What you should know

Can a thermos bottle go in the dishwasher? The honest answer is: it depends on the model – and for many insulated bottles it's a no. For our two IZY thermos bottles, too, the manufacturer gives a clear recommendation: clean by hand, not in the dishwasher. In this guide you will learn why that is, how to tell what is allowed for your bottle, how hand washing works in just a few minutes and what you can do if the bottle has already been through the dishwasher.

Contents10

1. The short answer
2. Why many thermos bottles shouldn't go in the dishwasher
3. How to tell what is allowed for your bottle
4. Hand washing in five minutes
5. How to make hand washing a habit
6. The bottle went in the dishwasher after all – what now?
7. Does this also apply to the closure and accessories?
8. Our bottles
9. Conclusion
10. Frequently asked questions

The short answer

• The manufacturer's information counts: Whether a bottle is dishwasher-safe is stated in the care instructions or on the packaging. If there is no information, it's better to assume hand washing.
• Our IZY bottles: According to the product description, clean by hand with warm water and a little mild washing-up liquid, not in the dishwasher – so that the surface and the insulation stay protected.
• Even with “robust” models: Even if a bottle is considered suitable, hand washing is gentler on the design and seals.

Why many thermos bottles shouldn't go in the dishwasher

An insulated bottle is more than a simple container. It consists of two walls, a space in between, an often printed or coated exterior and a closure with a seal. In the dishwasher, several stresses act on all of this at once.

Heat and prolonged wetness

A dishwasher cycle works with hot water, steam and a warm drying phase. This combination often lasts an hour or longer. Not a problem for plates, but for a bottle with a space between its walls and seals, it is a much greater strain than a short hand wash. Consumer portals such as Öko-Test point out that a machine wash can damage the insulating ability of a vacuum flask.

Aggressive detergents

Dishwasher tablets and powders are much stronger than a drop of washing-up liquid. They are meant to dissolve baked-on residue. On coloured surfaces, lacquers and prints, they can lead to fading, dullness or flaking over time.

The design

Especially with bottles featuring an art motif, the surface is an essential part of the product. The colourful floral design of the Van Gogh bottle or the playful Pip Studio pattern of the “La Dolce Vita” are meant to stay beautiful for a long time. That is one reason for the manufacturer's advice to wash by hand.

Seals and plastic parts

Rubber and silicone parts age faster when they are frequently treated with heat and strong detergents. A hardened or deformed seal makes the closure leak.

Stress	Dishwasher	Hand wash
Temperature	hot, for a longer time, with steam	warm, only a few minutes
Detergent	strong, for baked-on residue	mild washing-up liquid
Surface, design	risk of fading and wear	gentle
Insulation	may suffer depending on the model	no particular strain
Cleaning effect inside	water jet often barely reaches into narrow necks	brush reaches the bottom and walls

The last point is often overlooked: with slim bottles with a narrow neck, the machine's spray doesn't really reach the bottom. Hand washing with a brush is actually more thorough there.

How to tell what is allowed for your bottle

• Care instructions or product description: This is where the binding information is.
• Symbol on the packaging or base: Dishwasher-safe products often carry a symbol showing glasses or plates under jets of water. If it's missing, that's no free pass.
• Look at the parts separately: Sometimes only the closure or only the cup is approved. Read carefully.
• If in doubt, ask: the retailer or manufacturer, before you try anything.

Hand washing in five minutes

Instead of the dishwasher, a short routine is enough, and after a few times it runs quite casually:

1. Unscrew the closure and treat both parts separately.
2. Put warm water with a drop of mild washing-up liquid into the bottle, about one third full.
3. Use a bottle brush to scrub the bottom, walls and neck.
4. Rinse the closure under warm water and go over the thread with a small brush.
5. Wipe the outside with a soft, damp cloth – no scratchy sponge side on the design.
6. Rinse clear until no more foam can be seen.
7. Drain briefly upside down, then let it dry open and separately from the closure.

That is entirely sufficient for daily care. Stubborn deposits, odours or limescale rings occasionally need a household remedy such as baking soda or citric acid – but that still remains a hand wash.

What belongs by the sink

• a bottle brush with soft bristles,
• a small brush or old toothbrush for the thread,
• mild washing-up liquid,
• a soft cloth for the outside.

How to make hand washing a habit

The appeal of the dishwasher is obvious: load it, done. To stop hand washing becoming a chore, a few little tricks help:

• Keep the brush within reach. If the bottle brush lies right next to the sink, the step is much smaller.
• Rinse immediately. If you swirl out coffee or tea with warm water right after emptying, there's hardly any work left in the evening.
• Combine it with the washing-up. Do the bottle together with the first pot while the water is still warm.
• Choose a fixed time. For example every evening before going to bed – then it stands dry and ready in the morning.
• Two bottles in rotation. If you're on the go every day, a second bottle means you always have a dry one to hand.

The bottle went in the dishwasher after all – what now?

It happens faster than you think, for example when someone else loads the machine. No reason to panic, but a reason for a quick check:

1. Look at the outside: Is the design still intact, are there matt spots, bubbles or flaking?
2. Check the seal: Does it still sit straight, is it elastic? A quick leak test with water over the sink shows whether the closure holds.
3. Watch how it keeps warm: Fill in hot water and touch the outer wall after a few minutes. If it becomes noticeably warm, the insulation is no longer working as usual.

If everything is fine, keep using the bottle as before – and wash it by hand from now on. A single cycle doesn't necessarily cause damage, but regular machine washing increases the risk considerably.

Does this also apply to the closure and accessories?

For our IZY bottles, the care recommendation refers to the bottle as a whole: hand wash. With other models, the manufacturer may classify individual parts differently. If in doubt, follow the relevant instructions.

Our bottles

Our two IZY thermos bottles hold 500 ml each and, according to the manufacturer, are double-walled, made of rust-free stainless steel, BPA-free and taste-neutral, with a leak-proof screw cap. They keep drinks hot for up to 12 hours and cold for up to 24 hours.

• IZY x Pip Studio “La Dolce Vita” thermos bottle – playful Pip Studio pattern, comes in a round gift tin.
• IZY Bottles Van Gogh Flowers thermos bottle – colourful floral design inspired by Vincent van Gogh.

You can find both in the IZY collection. How to keep your bottle cool for longer in summer is explained in water bottle in summer.

Related reading: How to clean a thermos bottle: routine, household remedies and common mistakes · Thermos bottle broken? Test the insulation in three steps · Lifespan of a thermos bottle: what determines it and how to extend it

Conclusion

Whether a thermos bottle can go in the dishwasher is decided by the manufacturer. For many insulated bottles – including our IZY models – the recommendation is hand washing, so that the surface, design and insulation last a long time. That's less effort than it sounds: warm water, mild washing-up liquid, a bottle brush and five minutes are enough. And for narrow bottle necks, the brush is more thorough than any spray jet anyway.

Frequently asked questions

Can IZY bottles go in the dishwasher?

No. According to the product description, both IZY bottles should be cleaned by hand with warm water and mild washing-up liquid, so that the surface and the insulation stay protected.

What happens if a thermos bottle goes in the dishwasher?

Depending on the model, the design can fade, the seal can age or the insulating ability can suffer. A single cycle doesn't have to cause damage, but regular machine washing increases the risk.

How can I tell whether my bottle is dishwasher-safe?

From the manufacturer's information in the instructions or on the packaging, often with a corresponding symbol. If there is no information, it's better to wash by hand.

Is hand washing hygienic enough?

Yes. With warm water, washing-up liquid, a brush and then drying open, a stainless steel bottle gets thoroughly clean – with a narrow neck even better than in the machine.

Can I at least put the closure in the machine?

That depends on the manufacturer. For our IZY bottles, the recommendation of hand washing applies to the whole bottle.

Shop IZY thermos bottles

Personally written by Martin – founder of BeachAndSteam and sauna operator at Lake Kulkwitz for more than 18 years.