23 Sept 2015

How to fill a hot water bottle

Thanks to everyone for your messages about this #KnittingAhead series. I am glad you are enjoying all the ideas. I had a query about filling your hot water bottle, so here's the method my mother taught me, and mother's are always right eh?... (Well, that and the manufacturer's instructions of course!)

Firstly it is important that the bottle is emptied in the morning after it is finished, so we are starting now with a hot water bottle which is out of its cover and empty. So here's what to do:

#1: Fill a kettle with freshly-drawn cold water. Do not use hot water, as the hot water pipe often contains minerals that degrade the rubber of the bottle. If you don't have a kettle, then you can heat the water in a saucepan with a pouring lip, or in a microwave.

Heat the water until it is hand-hot (about 42ºC/108ºF). You do not need it to boil, and in fact if it does you then have to wait a long time for it to cool to an acceptable heat. Bottles can leak from time to time, so it is important that the water will never scald you if the rubber gives way. 

Many modern kettles have variable temperatures which allow you to start with a lower shut-off point. If you have an older-style kettle, then wait until the water is just starting to sound "noisy" and then immediately turn it off. 

Pour the water into a jug that pours well and add cold water until the temperature is right. You should be able to briefly put your hand into it without scalding. 

#2: Now hold the hot water bottle upright over a sink. Grasp it firmly by the top and carefully pour the water in until it is about 2/3rds full. 

#3: Hold the bottle at a slight angle and then gently lower it onto a flat surface until you see the water at the top. This expels all the air. Insert the stopper and close it firmly but without too much force. Press the bottle gently, then turn it upside down to check for leaks. 

Dry the opening around the stopper and any damp patches on the outside. Feel the bottle to make sure that it is not too hot. It should be comfortably warm, not too hot to hold at this point. If it feels a little too hot for comfort, then pour a little of the hot water out and run in some cold.

#4: Place it into its cover and prepare additional bottles if more are required.

Place two in each bed, one at the top with your PJ's wrapped around, and one for your feet. If you do this about 20-30 mins before you go to bed you'll be super comfortable when you snuggle under the duvet.

It is fine to gently hug your bottle while you are still awake, but don't press it too firmly or it could burst. For a child's bed, it is best to remove the bottle before they get in. 

#5: In the morning, take the bottles out of their covers and drain them completely. Hang them upside down to store and to drain further. It is a good idea for each stopper to be attached to its own bottle by a string around the neck, as different bottles can have slightly different threads and you want your stopper to be completely water-tight.

When they are not in use, store the bottles upside down in a dark, airy place. Always buy a good rubber bottle rather than the cheaper imitations and replace them every year or two. It's also a good idea to check the bottle really well before using them for the first time each season. Filling it with cold water and squeezing gently will soon show if any areas are compromised.

Hot water bottles come in all sorts of sizes and designs. You can use the Joules and Joulietta hot water bottle cover pattern for regular size and travelling size bottles, and also for microwave packs. I am not so keen on the microwave versions as they can get hot spots, but they do suit some people. However, don't place hot wheat packs into your bed as they can go on fire. These are great for sore necks and backs, but are not a substitute for a good old-fashioned hot water bottle.

I love hot water bottles and have fond memories of watching my mother go through the routine of filling them every night. I hope you enjoy yours too!

Happy Knitting!


  1. Thank you for posting this! I know it seems silly but everyone was saying don't use boiling water or hot tap water, but no one explained why not hot tap or what to do instead 😂

    1. Thank you so much! Glad that was helpful. Moira


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