Using a L7 water cooled radiator to heat an outdoor shower

Few weeks ago I hooked up my L7 to a 20L drum to see how hot I could get it. After an hour it got to 50 degrees Celsius, however it slightly leaked around the cap because I 3D printed a cap with a venturi pump built into it, It leaked about 100ml I would guess so it was cool to to keep an eye on it and see how hot I could get it. I was very impressed with it getting to that temperature considering it was just connected to a 20L plastic drum. So I thought I might try hooking it up to an outdoor shower.

This is the shower, its $250 AUD

On the back you can see what looks like a 1 inch brass nozzle, only one source of water so with how it comes you dont have hot or cold taps, so I will make it so you can have hot/cold how you like

Blue lines is hose with cold water, red lines are hose with hot water

Something like this I want to use brass with thread tape so A. Doesn’t leak and B. doesn’t break. Dont want to cheap out and have water all over my miner or radiator, even though I will protect it from any possible water or have a pipe break and the miner run with no water.

The push in lock fittings are actually used on the radiator already and they have been very good so I have ordered more to do this, along with more hose.

-Tee piece from the garden tap. One side will go directly to the shower as cold water, the other side will go directly to the radiator to go into the miner as cold water. Theres either a 4mm or 6mm male cap at the top of the radiator to put water in, so I will get a male thread to put into that and make it join a 1/4 male thread. To keep the drum as hot as possible I will want water to come in to the radiator, enter the miner then go into the drum.

-Hot water enters the drum from the miner. At the bottom of the drum there’s a 19mm cap, so I can take the cap out and put another push lock fitting with a male thread there. I will try to put 2 push lock fittings into the cap of the drum, one will take hot water from the miner and the other will send water back to the radiator. This will require the drum to be full, so I will have to make sure the water that goes from the drum to the shower has less flow rate than the water coming from the garden tap.

-Hot water goes from the bottom of the drum to a second pump.

-Water from the second pump goes to the shower, first going through a tap, then a check valve to ensure no water can go back into the drum or through the other side, then into the tee piece. The ball valve tap for both the hot and cold side will control the flow rate which will also obviously control the pressure and temperature as both hot and cold water mix together and go through the shower.

-And that final tee piece will replace the nozzle at the bottom of the shower.

My only concern is even though fresh water will enter the drum through the miner first, how much cooler will it make the whole drum. Like if I run the shower for 5 minutes, will the water go from 50+ degrees to 40? Im not sure. Its only a 20L drum and the pumps run at 11L/min so I think that will effect it. If this is a success I will consider getting a 200L insulated tank which will help with fresh water entering the tank and keep the temp from dropping. When I get everything here I will post updates. Any suggestions welcome!


Well fancy that, my uncle ditched his old hot water tank and left it to be taken. Stars have aligned

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My push in plugs came today - good quality. My 200L tank I can’t use I think it’s had some nasty stuff in it.

So just hooked it up to the drum and put a ball valve tap at the bottom. I turned the fans down to make the miner 75 degrees and the drum is extremely hot, like want to take your hands off it hot. I opened the valve to let a bit of water out and see how hot it was and I’d say it’s slightly hotter then my preferred shower temperature. Not to mention it doesn’t take long to heat up. To me this is awesome because we are all talking about miners becoming obsolete, but I can leave this as a lottery miner. Probs won’t replace my hot water service with this, just make it a secondary one. I’ll post pictures of it with the shower when it all comes but I’m pretty confident in it. If I wanted I could push the miner to 80 but I prefer to keep it under 75.

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Video update Reddit - Dive into anything

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Ok so the max temps with cold water flowing directly through the miner into the tank and water leaving the tank out into the open the max water temp was 40 degrees. This isn’t surprising considering the tank is only 20L and the water kept cooling down to about 36 degrees before I turned it off.

This was the miner temps before I turned the tap on

This was the miner temps after I turned the tap on and let water out the tank

I also ran the miner for an hour with miner temps in the mid 70s and stuck my sensor in the drum and the temp stayed at 49 degrees

I then put the sensor in my shower in my house and turned it on 100% hot and put the sensor in a cup and put it as close to the shower head as I could and let it overflow, and the max temp was 43 degrees.

I am confident in making this work. I will get a 1000 litre shuttle, even though I will only fill it to 200-300 litres it will make it easy, I shouldn’t need a breather valve because the water level should sit much higher and fill the miner + radiator first, and those shuttles are heaps easy to put holes in and some top hat grommets in to stop leaking. When I get that working and test how long the temps last for per 200L of water and am happy with that then I’ll get the shower

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