It’s 2020, autumn, and the pandemic did not miraculously resolve after the election. For those of us who believe in science and value the health of others, the only safe way to socialize these days is to take our meetings outdoors.

I suffer more from the cold since developing an autoimmune disease, but November in New England isn’t traditionally known for sedentary al fresco activities. Even hale and hearty young people become uncomfortable sitting still as the mercury drops much below room* temperature.

And, of course, we got weather like this in October!

The first step to staying comfortable outdoors is wearing appropriate clothing. It is always wise to bring at least one layer† more than one thinks is necessary for extended jaunts on cool days. Wear a cap, and bring your gloves, too, of course. But if the sun sets, or the temperature drops below 60º F or so, the amount of clothing required—or the need for expensive, highly specialized gear in which you may not wish to invest—can become burdensome.

Why I use hot water bottles at home and outdoors

I send my child to outdoor classes—and welcome visitors to our yard for socially distanced visits—with a cheap, simple, classic, soothingly warm hot water bottle. Adding a source of radiating heat beneath a blanket or tucked into a jacket can add hours of comfort for anyone, and, as a bonus, it also helps ease pain for those of us with arthritis.

Unlike a heating pad, you aren’t tied to an electrical outlet with a hot water bottle. And, while I also use microwaveable “warm bags” —which I’ve heard friends call “rice sacks,” “heat pillows,” and also “heating pads”— the grain filled type weigh just as much, yet cool down relatively quickly compared with the long sustained warmth of water with its very high specific heat capacity.

My history with hot water bottles

Before I married my husband, I’d never even seen a hot water bottle in real life. I knew what they were from old novels and cartoons, but hadn’t noticed they were still sold in stores.

Quaint and old-fashioned hot water bottles may be, but I’ve become a convert. I’ve found them readily available in major chains and tiny Main Street Mom & Pop drug stores across America. Ask the pharmacist—or the oldest person on staff—at your local shop, and you will probably get what you need.

We had the old rubber hot water bottle DH brought to our marriage for a number of years, but I never thought to use it. When we had children, his parenting naturally followed that of his own folks. Sick little boys need a hot water bottle by their feet, it turns out; modern moms who cuddle those feverish babes discover for themselves that a hot water bottle in a cold bed is almost decadently delightful.

With child number two, and the inevitable swapping of germs, a second bottle was acquired for simultaneous soothing. They looked a lot alike—classic red latex rubber—but their tops were just different enough to fit in each others’ filler holes yet leak tiny drips even when tightened. The next bottle I bought locally was a clear plastic model by Fashy with a very different cap shape.

Sharpie markings help with problems like this, but matching at midnight when your kids are sick is a bleary eyed burden.

For this reason, when the stopper cracked in half on one of our two hot water bottles this September, I decided to order several new ones at once to ensure the same brand and interchangeable tops. I also discovered that—as with most other forms of consumerism—Amazon has a much wider array of hot water bottles available than any local store.

I could get one in my favorite color!

In addition to three Hometop bottles in traditional latex rubber, I decided to review a few other options for my readers. As always, I rely upon my large-ish household to make good use of my shopping excesses.

Having six hot water bottles instead of just two means never having to send anyone to bed with cold toes, even if you sent one outside with a guest earlier in the evening and have a great and terrible fear of fomites.

I’ve mentioned the two most common materials for hot water bottles—classic rubber and modern plastic—but there’s a new option on the scene: the silicone hot water bottle. The pink kitty and the small, grey hot air balloon design bottles in my photo are made of silicone.

Here are the four specific hot water bottles I bought in September 2020 from Amazon.com, including links to the same seller listing when possible:

• HomeTop Premium Classic Rubber Hot Water Bottle (2 Liter capacity) in Cream, Red, or Purple with a Foxy cover
• HomeTop Premium Rubber Long Hot Water Bottle w/Soft Gray Polka Dot Fleece Cover (2.25 Liter capacity)
• Pink silicone kitty hot water bottle maybe made by Mr. Strong (430 mL capacity measured by me) as the only Latin characters on the packaging say “Cookie Cat, Hot Water Bag, Excellent comfortable life!”
• Grey silicone hot air balloon** hot water bottle with cover (520 mL capacity stated by Amazon seller)

Buying advice for hot water bottle

Size & capacity dictate how long warmth lasts

Your first consideration is how long you’ll want the bottle to stay hot at a stretch. Traditional hot water bottles can’t be reheated; you refill them again with hot water after they’ve cooled.

Smaller silicone models like my kitty or balloon design are great for a coffee visit, or to take the chill off cold hands at outdoor school on a day that’s rapidly warming up, but they won’t last more than an hour or two.

Remember that the ambient temperature—how warm the air around you is, and whether you’ve tucked your bottle next to your warm body under some form of insulation like a jacket or blanket—will affect the length of time your water bottle stays hot.

Traditional 2 Liter bottles, by contrast with small silicone ones, will still be warmer than ambient temperature by morning if you sleep with one under your covers. If I place one by my feet while working at my desk, it will offer warmth for at least half a day when buffered against the cold hardwood with a rubber anti-fatigue mat and covered by the down throw blanket I drape over my lap.

My largest capacity bottle is the long, skinny HomeTop model which holds 2.25 Liters (80 fluid ounces.) This is my favorite style for warming a cold bed at night, but it is spectacularly tricky to fill at a sink and particularly unwieldy to use when moving around. For me, with arthritis in my hands, I require assistance to fill this bottle without dousing the outer fabric cover in the process.

On Amazon, I also noticed a brand called Peter Pan offering bottles that hold a whopping 90 (2.6 L) and 100 (2.8 L) fluid ounces of water. I was tempted, but both higher prices and skepticism about my ability to manage such a large filled bottle kept me from clicking Buy Now. If anyone has tried these behemoth bottles, I would love to hear a review in the comments!

More water means the bottle will warm you for longer.

Then again, water is heavy. One of my standard sized hot water bottles weighs 4 -1/2 pounds when full; even little miss pink kitty tips the scales at almost 1 -1/2 lbs. Filled, a hot water bottle is a bulky thing that requires some delicacy in handling. You shouldn’t sit on, step on, or sharply bend a filled one. Stabbing is right out of the question!

Balance your need for extended heat with your intended bottle’s size and weight.

Material matters

Rubber (latex)

Traditional rubber hot water bottles are made of latex. If you have an allergy, like I do, you won’t want to handle an uncovered bottle with bare hands. For me, a covered latex bottle does not trigger a reaction, but I get that itchy allergy feeling and develop a rash on my hands if I touch the bottle itself.

So why did I buy rubber bottles at all? Rubber hot water bottles are more flexible than PVC plastic, and I also strongly prefer not to consume any more plastic than absolutely necessary. Once a latex rubber bottle is in its cover, I find its squishy texture more comfortable touching my body than somewhat more rigid PVC plastic.

My research has also suggested that a rubber bottle is less likely to become brittle with age vs. a plastic one. Aging rubber might also eventually leak, but I believe an old rubber water bottle is less likely to burst and more likely to develop a slow leak. Since these bottles go to bed with members of my family, that difference is meaningful!

Note that I don’t have definitive facts to back up this conclusion, but it’s one I’ve come to gradually based upon living with a few bottles and reading other people’s experiences with them on the internet. Your mileage may vary!

Red rubber is the most typical color for the original modern hot water bottle. The fact that pencil erasers are also pinkish red makes me think there’s a reason this color is so common for rubber items, but a quick internet search hasn’t enlightened me. Rubber cannot be produced to be transparent, so, if you’re looking at a clear bottle of any color, it is plastic, not rubber.

I lumped my red, white, and purple HomeTop bottles into one “product” in my bullet list because they carry the same imprinted product ID number and appear identical in every way except color. Covers made and sold with one will work with any other bottle from this brand.

Never put a rubber hot water bottle in the microwave. Natural latex rubber bottles are refilled with hot water from a tap or kettle, not reheated directly!

Plastic (PVC)

My Fashy plastic bottle has outlasted at least two rubber bottles, mostly due to issues with or around the cap for the rubber models. The clear Fashy bottle has the largest fill hole diameter of any other hot water bottle I’ve tried by about 1/4 – 3/8″. If your hands shake or your eyesight is very poor, Fashy may make the best bottle for you to fill on your own due to its more generous opening.

After many years of use, there does appear to be a tiny stained area inside my clear plastic bottle. I think it’s a stain, not a mold, because it doesn’t change and isn’t growing, but being able to see what’s going on inside is another benefit to transparent plastic over rubber or silicone.

If you’re the type to forget to clean an item like a filled hot water bottle, plastic may be your ideal material due to the ability to view what could be growing inside.

Never put a plastic hot water bottle in the microwave. PVC plastic bottles are refilled with hot water from a tap or kettle, not reheated directly!

Silicone

The newest entrance into the hot water bottle market is flexible silicone. I’ve written about using silicone bakeware before, and I have lots of lunchbox organizers made of it, but this was my introduction to its use for hot water bottles. With more than a month of use, I’m a definite fan!

The greatest benefit to the silicone bottles is an ability to microwave them to reheat the water inside. Since all the silicone bottles I’ve found are relatively petite compared to the old 2 L standby, this attribute is more important‡ for them than it would be for a bigger model.

If you choose to reheat a silicone hot water bottle, take care to check your microwave’s wattage. Consider heating at less than 100% power, and start out with short increments of time while you figure out the best way to re-warm your new bottle.

I use 80% power on my 1000 Watt Oster microwave when heating pink kitty or grey balloons.

There are reports of people blowing up their silicone hot water bottles in home microwaves, but I suspect that is more often user error than manufacturing failure.

Silicone hot water bottles are the ONLY type you can heat in the microwave. Silicone bottles may ALSO be refilled with hot water from the tap or a kettle if that’s more convenient than reheating one directly.

How to fill hot water bottles

For the most part, I fill my hot water bottles about half- to 2/3- of the way with hot tap water (set to about 130° F or 54° C on my hot water heater), then I top them off with hotter (but well below boiling) water from my (boiler style) electric kettle.

My Zojirushi kettle has a temperature readout, so I can ensure I’m not about to melt my hot water bottle or burn myself.

I also tend to top off the kettle with fresh filtered water from the tap just before filling a water bottle, and that brings the temperature down, too, below my preferred hold temperature of 195° F. Combining tap water with this hot water probably results in a hot water bottle at around 160° F.

The ideal temperature for warm heat therapy is around 130° F, so why don’t I stick with straight tap water? It is really important never to fill a hot water bottle with water so hot it will burn its user!

First, because I have to run the water for a fairly long time before I get fully hot water at my 2nd floor kitchen tap.

Second, because I often end up puttering around the kitchen (or driving my kid to school) before the bag sees use anywhere near a human body. I make the hot water bottle warmer than I want it to be when I finally get around to using it because entropy.

Third, it’s actually rare for me to use any hot water bottle directly against my skin. Instead, I’m usually placing them alongside my warmly clad body draped in multiple layers of clothing. I keep my thermostat turned down and wear long johns and sweaters at home. I’m less worried about burns than I would be if I used a hot water bottle on bare flesh.

Finally, filling a bottle neatly at the sink can get a bit tricky, especially as the water level rises. My sink often has a few dirty dishes in it, so there are physical obstacles to the large bag hanging down into its void. Also, getting water all over the outside of the hot water bottle makes it harder to use, especially if going outside where wet means very, very cold if you’re wearing casual cotton.

Topping off a bottle at my particularly tall Zojirushi kettle means I can hold it hanging straight off the counter and clearly see the stream of very hot water flowing in.

To fill a hot water bottle without my beloved boiler style of electric kettle, you may want to try pouring water from a narrow spouted kettle of the gooseneck type used for coffee pour overs. Whatever you use—sink faucet or kettle spout—should be easy to aim. You want a precise stream of water that you can direct accurately into the sometimes small fill hole of your hot water bottle.

The hotter the water you choose to fill with, the more careful you should be to avoid splashes and spills when filling. Burns send nearly half a million Americans per year to the hospital, and thermal burns are the most common type.

Care & feeding of hot water bottles

We’ve had hot water bottles last at least a decade, and others have died within a few years. Most materials deteriorate when subjected to high heat—yet another reason to avoid boiling water in a hot water bottle!—and also from UV light degradation.

That said, my bottles live in front of a sunny kitchen window all winter, and they still seem to last fairly well. I do put them away in a dark drawer over the summer, however.

Avoid storing hot water bottles next to a radiator or the stove. High, direct heat is particularly bad for both natural rubber and plastic.

After use, empty the water from hot water bottles as soon as possible. I used this water on houseplants, or to rinse those dirty dishes awaiting my attention in the kitchen sink.

Allow your bottle to dry thoroughly, and store it with the cap off whenever possible. Try to store your bottle hanging upside down so every drop can drip out, or you may end up with a moldy, smelly object that’s impossible to clean.

Many hot water bottles and their caps have a hole for hanging them up. If your cap has a hole, consider tying a string to it and looping it around the bottle’s neck for storage when it isn’t in use. Without its cap, a hot water bottle is useless.

Tip: If using thread to attach your stopper or hang your bottle vs. thicker string or cord, use extra strong Button & Carpet or Craft thread for longevity.

I label my hot water bottles and their caps with a description or a number or even just a colored dot if the correct match isn’t drop dead obvious. (E.g., pink kitty water bottle is the only one with a pink cap, so I didn’t mark that one.) Using a stopper that almost—but doesn’t quite—fit your bottle can result in insidious leaks that might ruin your mattress or shorten your comfortable tenure outdoors.

Price is no object?

While admittedly I balked at the $30 – 40 price range for the Peter Pan line of hot water bottles, the vast majority will run between $10 – 20. Buying even the cutest, most environmentally friendly hot water bottle is unlikely to break the bank.

This is also a case where most bottles in that reasonable price range will perform absolutely identically. There’s no need to pay more for better performance. Figure out the size (or weight) of bottle that makes sense for your situation, and you should be able to select any right-sized bottle with good results.

I must admit that the two most expensive hot water bottles that I purchased in September have gotten the least use at my house. Pink “Cookie Cat” kitty ($17.80), while by far the most photogenic, is less convenient to hold than the comparatively dull grey balloon bottle. And the long, grey 2.25 L grey dots bottle ($19.99) is my favorite to sleep with, but often too much trouble to fill come bedtime.

Since I often have a standard bottle at the couch with me in the evening, I routinely carry that still-lukewarm one upstairs and use whatever warmth remains to pre-heat the chilly part of my bed where my aching feet are about to end up.

In spite of all that, the pink silicone kitty cat bottle sits next to my kitchen sink looking adorable all the time. I probably wouldn’t have purchased it just as a tchotchke, but it meets the brief. This Cookie Cat bottle was also by far the most beautifully packaged*** one that I bought, and it is eminently suitable for gift-giving.

For those whose budget won’t even stretch to a $12 standard bottle, I’ll point you to a travel-related post I wrote a few years ago. If you own a metal drinking water bottle, you might be able to make it work as a hand-warmer in lieu of purchasing anything new at all.

Covers for function & fun

Aside from the absolute need for a cover on a latex rubber bottle for those of us with contact allergies, you can choose to cover your hot water bottle or not when using on clothed skin. This may be the one area in which price will determine quality.

I don’t have a lot of acrylic fibers in my wardrobe. When my child dropped the hot air balloon design cover right onto a dirty dish in the kitchen, I threw the cover into the next load of laundry. That turned out to be a load of towels. The cover came out a little worse for wear. It still works, but the texture has changed (less soft and kind of “crispy”) and the shape is a somewhat distorted.

To be honest, I like the silicone bottle better without its cover, so it’s gone naked most of the time since it’s aggressive laundering.

The HomeTop grey “foxy” cover is also acrylic, but it feels much thicker and of higher quality. I haven’t needed to wash it yet, so I can’t speak to how it will hold up. I do plan to add Foxy to only delicate wash cycles with wool sweaters and socks, NOT to a load of towels for which I’ll use hot water or the Sanitize cycle. I’ve learned my lesson with the hot air balloon débâcle.

The HomeTop fleece “Dots” cover has the most agreeable texture to my touch. It feels like a high quality fleece. Again, I have yet to launder it, so I can’t say whether it will pill or stiffen later on, but I have high hopes for it.

As a rule, I try to treat covered hot water bottles as “clean” items, like I might my bed pillow. I don’t set them on soiled surfaces or expose them to the outdoors. I send hot water bottles outside wrapped in a simple kitchen towel that will be trivial to wash after use. A plain pillowcase, too, can be used to cover any bottle, and it will stay in place more readily than a folded towel.

Carrying hot water bottles out & about

Using an insulated tote to schlep your hot water bottle will gain you valuable minutes of soothing heat once you reach your chilly destination.

For traditional 2 L bottles, I carry mine in an old Pyrex Portables insulated carrier that came with a glass casserole dish. Made for safely bringing oven-hot meals to potluck suppers, this bag is uniquely well suited for the heat and weight of a full hot water bottle. Using the microwave hot pack that came with the Pyrex set further enhances heat retention while en route.

Smaller silicone hot water bottles travel to school in a traditional insulated lunch sack. If I’ve also packed hot tea or a warm meal in my child’s lunch, that flask will join the hot water bottle in one lunchbox while chilled food goes in another.

To prepare for COVID-19 era guests, I first pre-warm our smallest Igloo cooler—a 17 quart/16 L/24 can unit—by putting a microwaved heat pack or hot water bottle inside at room temperature. I.e., don’t leave your cooler in the cold garage for this step!

When our friends’ arrival is imminent, I fill a large hot water bottle for them, and I typically prepare a carafe of coffee or tea and throw in a few snacks for those who are willing to touch comestibles from someone else’s kitchen during a pandemic. The sturdy little hard-sided cooler keeps the hot water bottle and beverages warm until wanted, and it acts as a handy side table next to our camping chairs in the yard, socially distanced from our perch on the deck.

This particular size Igloo cooler is also perfectly sized to sit behind the seats in smaller cars, so it would be my choice for family outings if I wanted to bring hot water bottles for everyone on a car trip.

Warm wishes for cold bodies everywhere

If you’ve never tried a hot water bottle, now is a great time to give one a whirl as so many of us spend more hours meeting outside and working from home. A hot water bottle will definitely improve your comfort level while socializing outdoors this winter, and you may also find yourself able to lower your central heating bills by adding one to your work from home routine.

Best wishes for toasty toes and warm- and flexible- fingers to readers far and wide!

♦

* Roughly 68º F or 20º C if the Oxford English Dictionary is to be trusted as a source, which, speaking for myself, it generally is.

† A rookie mistake is to layer only on top. Yes, put on that jacket, but also consider a pair of long johns, tights, or leggings beneath your trousers, or add wind-resistant “rain pants” on top. Unless your overcoat reaches your ankles, it’s probably only warming the top 50% of your body.

** I bought my bottle from seller Xboun who now appears to have only a smaller size in stock. I’ve linked to a bottle that appears identical to mine from an alternate seller.

‡ Water holds heat well, but a larger volume of water is going to stay warm much longer than a smaller quantity can due to its greater mass. If you want to learn more about why this is true, start with the “Heat capacity and heats of vaporization and fusion” section of this Wikipedia page. The study of physics is not strictly required for the selection of a hot water bottle, however. 🙂

*** Though a sticker covered what I guess was a Japanese description of the item inside, a short English language page was included in the box. The outer carton was even designed to live on as a decorative tissue box. The exquisite attention to detail in the packaging is what makes me believe the product was made for the Japanese market.

And as a special treat (?) for those who read all the footnotes, perhaps you can guess what a teenage boy thought the pink kitty water bottle resembled most when viewed from above? Try covering the right half with your hand if it isn’t obvious. Sigh…