Turn an Old Coffee Maker Into an On-demand Water Heater (nevermind)





Introduction: Turn an Old Coffee Maker Into an On-demand Water Heater (nevermind)

Update:  Nevermind this one.  Too many electrical shock risks to make it advisable even as an experiment.

Hey guys, this was a fun and novel idea I had but on retrospect, I don't think it's really something safe enough to recommend for people to try for realz, so I am deleting it...

Thank you for reading!

Step 1: Are You Forgetting Something?

Did you read all the safety warnings and follow them?

Are you sure you want to do this?

Did you feed the cat? 


Step 2: Bathtime

Fill up the tub as usual. 

The initial water temperature of the bath was 96 degrees.

Step 3: Enjoy a Long Soak

Read a book or watch all the Sketchup tutorial videos from the comfort of your nice warm bathtub.


Step 4: How Effective Is It?

Thank you and stay safe.


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    I actually made a homemade water heater using a coffee maker and some other supplies. I travel in a motor home and do not like using LP gas so I ripped out the gas heater and built a rather cheap but efficient water heater. All in all, I spent maybe $60 to build and took a day to construct. I made a supply list and step-by-step instructions but it's not letting me add photos. I made a 20 gallon tank and it takes about 6 to 8 hours to get around 110-130 degrees. The only problem I have had with it so far is if I use well water, I have to clean the water lines once a month as lime and calcium build up. I use vinegar to clean lines.

    1 reply

    Awesome, good to hear that this idea can actually work. I got so much flack for this one that I deleted most of the article. Maybe you will post an instructable that people will appreciate.

    Used this years back to heat a hot soaking tub for my wife. You don't need a pump just put the coffeemaker at the water level of the tub and add a siphon hose to put the water back in the coffeemaker tank, that will make the two water level stay equal. Works great except the pot would calcium up after about 2 months of continual use and have to be replaced. I've since gone to a 5 gal bucket heater and a waterbed thermostat teaked a bit to raise the temp to 110 degrees.

    1 reply

    Interesting approach. Reminds me of a guy I know that used the heating element from an electric hot water heater heater to achieve the same thing.

    As far as I know he is still alive.

    Well this is disappointing. Heck, quite a few things here are a 'bad idea if you don't understand the risks'.

    1 reply

    Yeah, I tried to delete this one, but it was in a contest, so I couldn't

    What is the aproxima GPM output of hot water? Thanks. I was just wondering how long i am going to have to wait for a tub to be filled. I have a small 100L tub i want to fill for my camping expiditions. due to the girlfriend not wanting to camp unless she has hot showers/baths everyday. Thanks

    Can someone say sketchy? Haha, don't kill yourself with a coffee maker next to a bathtub.

    So did I. Anyone want to loan me a cat so I can feed it and get past step 3?

    Why not READ the instructable before submitting a critical comment?

    "Not sure it wouldn't be easier just to turn on the hot water to re-heat the bath"

    The FIRST PARAGRAPH tells you why he does not do this.

    I have EXACTLY the same problem AND I have a spare (and gutted) coffemaker I was using as a distillery. I will be lounging in warm water all night!

    1 reply

    Sorry for overlooking that point, but I wasn't being critical. I love the idea.

    Of course! That's why we had to feed the cat! He's our TEST BATHER!

    You don't need to start a siphon the coffee maker already does that normally when you use it to make a pot of coffee. That is why the water in the tank in the back of the pot doesn't get hot and all the hot water ends up in the pot. The key is there is a ball valve inside the heating element so when the water heats up it expands and creates lower pressure on the hot side drawing in the cold water past the ball valve which in turn gets heated up. That is why you don't have a pump on the coffee maker in the first place.
    The ball valve is also the part that gets kludged up with lime and you have to clean it with vinegar or it gets too hot and you burn out that little heat fuse. I like the bike tire (cheap and easy) but it might be better with silicone tubing to withstand the heat hate to have the tube leak in the middle of a nice bath.

    Interesting project, but how big is your water heater? Unless it is teeny tiny, you should be getting a lot more hot water out of it. Perhaps a element is burned out or something.

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    It has just enough capacity to fill the tub once only. It requires a 30-40 minute wait to heat up all its water again.

    wow, that is quite small.

    Used hot water heaters really are not that expensive. As long as the tank is solid, the rest of the tank is pretty simple.

    I assume you mean the hot water outlet of the coffee maker and not the tub.