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In-suit hot water system

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Jul 7, 2002
At CAFA`s hompage you can see Mandy-Rae wear somekind of a "in-suit hot water system". It`s an interesting idea. Does anybody have any information about this ?

I don't know what she's using, but I can tell you what I have used in the past.

There are a few companies that make electric heaters for diving- mostly scuba. I had one with a pad to go in the small of my back and ran off of a battery pack. This would warm up the water by my spine and every time I would move it would push warm water around through the rest of my suit.

I used it a few times with my wetsuit, but I had purchased it to use with my drysuit. It plugged in and heated up part of my underwear. Now, there are better systems, that plug into a full set of electric underwear, and run off of a battery pack. There are some rebreather divers that I know who are pulling 2+ hour run-times, to 320', in 40 degree water who are using them along with thinsulate and argon. They were doing some deep survey work and would stash extra batteries by their stage bottles in case of failure on the way up.

My system was made by a, now defunct, company called Reptative Diver. DUI is now making some systems, and there are others, whom I can't remember, as well. A quick search on the internet for 'electric drysuit heaters' should help you out.

For ice divng we keep coolers, and jugs, full of hot water around to pour into our suits as the day goes on- this would be the cheap way to do it.

Another, sometimes oily, way to do this, that I have seen some divers do, is to attach a hose to a boats hot water exhaust port, part of the engine cooling system, and run it down your suit.;)

Thanks Jon, but I was thinking more spesifically about the equipment Mandy-Rae is using in the pic of the week. Photo by Tom Lightfoot. Take a look.
I have used hot water suits/systems for commercial diving. Just wonder have one could use it for freediving.

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Luc rigged up the system last year and dusted it off for Mandy to use while training for a competition we had in late November. (insert teeth-chattering emoticon here) Next week's freedivecanada Pic of the Week should explain it a bit better.

This week's picture shows the tubes that go under the suit. The inlet is at the wrist and the tubes run down to a Y where hot water exits at the thighs. I think I'd be inclined to run the tubes to the armpits or back. Luc ran the tubes right down to his feet when he was using it because that's where he had the most problem with cold.

The source of the hot water is a big sytrofoam box filled with expanding foam. There's also a 3 litre container of hot water and a hand-cranked pump.

The system delivers heat as promised and the water does stay hot for a long time. The trouble is that the styrofoam box is pretty bulky and has a strong tendency to float away.

My own system which is hightly reliable and highly portable involves a cup or two of coffee in the morning and a bottle of dilute ribena just before suiting up. :)

There was another semi-local tech diver who made a hot water system a few years ago for some 300' + ice dives he was doing up in Lake Wazee.

It consisted of a portable hot water heater, like for a camper, and a pump system along with 300' of graden hose to pump 150 degree hot water down to him at depth. This allowed him to thaw frozen regs and run the hot water over the outside of his dry gloves to warm up his hands.

The whole system was huge, I actually have some pictures that I took of it buried in an old photo album somewhere.:confused: Since it just sat on the surface of the ice he didn't have to wrooy about moving it onto a boat.

What I had used was much smaller. It was battery operated, as opposed to a whole warm water pump system. You could leave the pad inside your suit and only plug it in to a surface battery while doing your breath-ups- it has wet puggable connectors.

They also make gloves and socks that attach into the underwear part of it- it's basically a nicrom wire stiched into whaterver type of heating pad you want.

Here's a link to a company that's still in business:


and here's a photo of it:

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Thank you for that info Tom.
Jon, that eletric heating system looks interesting. Can`t help dreaming about this system integrated into a wetsuit :)
Electric system

I seem to recall at our November competition that Eric was talking about developing an electric system with the heater wires integrated right into the wetsuit and with the batteries as weights. I don't know if he's made any further progress on this idea but it would certainly be a sweet system.

an electrical heating systems what we could use over here in switzerland... our const weight training lake has got 8° celsius now. at the surface... the best way to stay warm for me is to simply not letting any water into my suit. works fine with an opencell tailormade suit that fits well - until the first turn at depth... but the real problem zones are mostly hands and feet. i wanted to try chemical hand warming bags but haven't found in the stores yet. but this could be a good solution for the hands-and-feet-freezing-:(-problem...

yours pat
Has anyone used those chemical heat pads that Pat was referring to? I thought they were air activated and therefore wouldn't work underwater, but I've heard others refer to them as well.

I'm going diving tomorrow, water temp 33-34F... I'll give them a try!

For years we have been using 're-usable Sodium Acetate' heat packs under our wetsuits:


They will work well for about 20 'diving days' in cold water, then their power starts to fade a bit. I'm pretty sure I racked up 80 'diving days' on a pack, but by then it was getting really less effective. But, they're so cheap, just get more of 'em. You must shroud them in a cloth like bag otherwise they will burn you (54C). They start out as a liquid (in the plastic). You bend a metal disc inside, then the pack solidifies (crystallizes) and gets hot (54C). Once the pack has finished generating heat, just boil it for 1-2 hours and it will liquify again. Over and over.

They stay warm in icewater diving conditions for about 1-2 hours, depending on how much cold water you have flowing through your suit.

You really can't go wrong with the thermo-pads. My only complaint is that they can only really be used along your back or stomach or chest; they are too big for the hands and feet, unless you have HUGE three finger gloves.

Eric Fattah
BC, Canada
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Thanks Eric!

What sizes did you use? just the little 4"x4" ones, or bigger? I'm gonna get some of those for sure!

thanks eric - exactly what i was looking for. as it seems you have used these Sodium Acetate packs for a long time. i absolutely have to get some. i am simply wondering if there aren't smaller ones than you describe.

by the way: i have made good experiences with 3M cold/hot packs in static sessions. i apply a warm pack in the lower part of my back and wear a thinner suit and get the benefits of lower peripheral temperature without having the feeling of beeing cold.

in constant weight training though i mainly have troubles with freezing feet and hands. so i plan to apply thermo-pads to feet and hands. i hope i'll find small enough pads to fit in my socks and gloves.

yours pat
We use only the 8x8 and 8x16 heat packs. The 8x8 can be purchased with cloth covers (convenient), but so far we had to make our own covers for the 8x16, or, alternatively, use two cloth covers of the ready-made type.

Eric Fattah
BC, Canada
Their site offers 4x4 pads now specifically for hands and feet... woohoo! that'll work perfectly!
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