Home Made Hot Tub for the Football Tailgates!

While enjoy a few drinks at a football tailgate during the Fall of 2008 season I had one of those light bulbs light up over my head!  It seems a lot of my ideas show up while consuming beverage.    

Some Frat guys at another tailgate had a truck bed full of cold water...  They thought they were the smartest guys in the world.  So I decided I could out do the Frat guys.  Being that I live in Montana and the weather dips well below the 20's in November I had a challenge.  I started acquiring parts from all over the place.  I got a 150 gallon stock tank from a buddy out in Minnesota when I went to his wedding.  It measured  4ft Diameter and 2 Ft deep.  It fit about 3 people comfortably and 6 uncomfortably!!  We used this small hot tub the first year and upgraded this last season for a 9ft Diameter hot tub!  Go big or go home!  Enjoy!

My interview with the news station.

Step 1: Find a Trailer and Suitable Tank

Living in Montana has its perks.  One being friends that have farms and trailers you can borrow for free, and two, local Ranch supply stores that will let you buy and return 1000 gallon stock tanks!

The tank is a cattle stock tank.  We had maybe 750 gallons in it.  Don't over fill it or else it will overflow everywhere when people get in it.  We had to ratchet strap it down with lots of straps.  And to prevent to much sloshing during transportation we had to strap a few boards onto the front and back.

Step 2: Insulation Is Key!

Since I work Construction I was able to acquire lots of blue foam board for free.  Believe it or not this was all destined for the dump! 

We lined the top of the trailer with two inch thick foam boards.  Make sure everything fits snug underneath.  The weight of the hot tub and a big enough gap could lead to a crack in your tank

The 1x2 foot strips of foam we lined the outer edge of the hot tub with. We ran a ratchet strap around them to hold them in place.  

We also added some fiberglass insulation in a plastic sleeve around the bottom as well. 

The half circle is actually 2 half circles of 3/4 inch foam board.  This made an 8 foot Diameter circle.  We laid this on top of the water to insulate it.  In the end we actually threw all the extra foam we had on top to help insulate.

Insulate All PIPES!!!

Sorry there isn't a lot of pics... I decided to make this instructable 3 months after the project was over. 

Step 3: Pump and Heat Exchange

I picked up this pump at a pawn shop for $60.  This pump straight up screams!  No literally it is noisy as hell.  I wanted the inlet as big as possible.  The more surface area the less suction power.  Preventing toes from getting sucked up!  It is a 1/2 HP Wayne pump.  I put the4 way splitter on the outlet side.  this helped to lower the pressure so the water moved slower through the copper coils.

Key thing with the pump!!!!  Always push water through your heat exchanger never suck through it.  The water can get ridiculously hot sometimes.

Insulate everything as well.  All pipes and hoses should get insulated.  The more the merrier!

The BBQ grill I picked up on the side of the road for free.  It really is amazing the stuff you find on the side of the road in a college town.  I had to weld the hinges cause the bolts were loose but rusted tight.  I also welded a few chunks of angle Iron in to raise and strengthen the grill.  If you are going to run Charcoal make sure you have a lot of airflow.  You don't want to kill the fire buy using a gas grill.  And gas grills don't work... Tried it the first year.  It was very slow at the heat exchange.

There is 75 feet of 1/2 inch soft copper tubing in this grill.  I used a pot to slowly wrap the copper around.  Careful when doing this!!!  Soft Copper likes to kink. Run the copper out far enough from your grill so you don't melt whatever is attached to it. 

Turn your pump on first then, Fill the grill with Charcoal and set it ablaze!

Step 4: Sit Back and Relax!

Enjoy The 107 Degree water with friends!

It took about 1 day to raise the temperature from tap temp which was around 40 to 107. 
The temperature outside while this was heating up never went above 36.  So I would say things went fairly well!


****I would like to caution you as well to not stop the pump.  We had an accident and cracked the inlet line.  had to shut the pump down for a good 5 minutes.  When we turned it back on it flash boiled the water for about 15 seconds.  And all the copper was constricting with the extreme heat difference.  It could also cause a blow out in the copper.

**** Another side note... I feel dumb about this one!  When adding charcoal to the hot tub in your swim trunks... Don't slip on the Ice into the 400 deg BBQ... 2nd degree burns to the back!  Very painful!  Wasn't even that drunk... : )

Comments

[buck2217]

Madness -- but cool all the same

[SuziT9]

So awesome! I spotted this picture and thought, "That looks like Montana!" Then I saw you were all holding GO CATS thundersticks and knew you were here in Bozeman.

This project is awesome; is it still around? ~Hi from Bozeman, and Go Cats!

[Fitzcarraldo]

Why not up the ante next game season by adding bubbles to that tub?  In the same way that bubbles transform Plain Jane white wine into magical champagne, they can turn your tailgate lobster pot into a tingly, roiling cauldron of excitement.  For a stock tank as big around as yours you probably need the biggest wet/dry vac you can get and 2 inch hose to run around the wall of the tub and to reach the vac.  But hell, you're taking the vac back to Walmart after the game anyway, so who cares what it costs?  It would definitely cool your water down at a faster rate than without bubbles, but you can offset this somewhat by placing the vac inside the Burger King crown guy's car with the heat set to full blast.  Now you're blowing 95 degree air into the tub instead of 25 degree air.

[glen.relaxnation]

You should check out the Kiwi Tub www.kiwitub.com It's a great commercial version of this idea. Very portable and durable. I hope to get one myself one day

[Todd Harrison]

That looks like a ton of fun!

I have been heating my in-ground pool for over 5 years with a BBQ grill. It was slow so I build a "Cajun conversion" that use two 200,000 BTU Cajun propane burners and now it is much faster.
See details www.redneckpoolheater.com

My Cajun conversion is portable and would heat your hot tub in about 2 to 3 hours. Plus you can turn off the flames if you have to maintenance anything and not damage your pipes. It would be a lot safer and easier to work I would think.

You might want to also take a look at all the others that have built pool and hot tub heaters on my "other photos" page.

[Rainh2o]

i built a small version of this once...took me all day...how long did it take to build these? Thats a lot of sweating joints!

[Todd Harrison]

40 hours

[t.rohner]

Very cool
although it's not a very detailed instructable, it gives a general idea of how to do it. I was thinking of something like that for a while myself. Mine would be stationary though. Since it gets cold here as well, insulation will be important. I also want to be able to either heat it with wood/charcoal or with my military gasoline stove. (It's like a Colemans camping stove, just a lot bigger. It has some 20kW power.)
So i could fill some 3 gal of leadfree into the stove tank to preheat. Then while sitting in the tub, enjoy firing it with wood and even grill something on the fire. There is a design on instructables where the coil sits in a converted propane tank.

[CrLz]

Hot! _{no pun intended}

[wolfkeeper]

I was wondering if you could use the cooling loop of an engine; you could drain it down and plumb it straight in and then clean it up with clean water. The engine already has a heat exchanger and pump in it.

[pdxcascadian]

i wouldnt use any part of a radiator or heater from a car, theyre usually full of all kinds of residual gross/bad stuff. Lead, antifreeze and salts.

[oppie]

A friend made a portable shower to take to a motorcycle meet. (not all bikers are grungy). He made a heat exchanger connected to his truck cooling system. Basically the same as a marine engine heat exchanger, it was a tank that contained copper coils (marine units are all stainless steel). The tank was in the antifreeze engine loop and the coils heated the wash water. Was the only hot water in the area and he made lots of friends...

[s_phillips]

Someone who makes copper coils for beverage purposes once told me to keep the copper from kinking, you can cork one end and fill the tubing with sand. I would think you could use salt instead, then what didn't flush out would dissolve and keep sand out of the works.

[JeremyNYC]

another option, quite cool... www.dutchtub.com. you'd have to come up with a pretty cool transport solution though.

[spiceyweasel]

.......Is that a hot tub, or a still in disguise?

[freecell64]

Think you could use a in ground hot tub shell built in to a frame?

[jblessf]

Most in ground or framed hot tubs are made of acrylic.. When made of acrylic the tub has to be kept level and not moved, because it can be misshaped and then crack and come apart. So you have to use a material that will have some movement properties. This idea is great!!!

[spiceyweasel]

I would say you should take the advice of the good people of Bowling Green Kentucky who build Corvettes and "Wrap your ass in fiber glass" as the saying goes. Plenty of structural strength if you reinforce it with carbon fiber and metal strips and you can form it any way you like. I would suggest making it sit lower on the bed frame and make the wheel wells seating areas in the tub. It will greatly reduce the ride height and put less stress on your truck to tow it. You have inspired me to build one. I will make an instructable project out of it, too. Thanks.

[palmerpirate]

Needs a flux capacitor. Turn that baby into a time machine!

[patrickcleary]

I think you mean, "Needs more Chernobly!"