outdoor hot tub ? Brainteaser

[IleanasColors]

Hello All,
Not really sure where to post this one. Now before I start let me just give you some working guidelines. This is my Fathers idea ( i want no credit ),
and yes he is crazy. Thinking outside the box is a life long motto for him. And no matter what we say he will pursue this project!.
OK here is the brain twister:
1.He has a pond in north/western NJ.
2. he is going to build a outdoor under ground hot tub. figures if he digs it so bottom is below frost line water won't freeze. figures 3 1/2 ft. maybe 4 ft? with a unfrozen water line of 6" at the bottom.
3.He has no running water. but does have a well ( a bit close to pond for me but if your only rinsing cups and making coffee who could it hurt?)no power except large propane tank, and a decent generator.
4. figures he can run gas line under ground and heat tub from below.
5. is considering using heaviest possible sheet metal he can get for tub, with wooden benches to sit upon.
6. No whirlpool jets (at least he is slightly realistic about this ) .
Anybody up to the challenge of coming up with a CHEAP (did i mention cheap was another rule?) and better way to do this?

 

[Bob NH]

Anybody up to the challenge of coming up with a CHEAP (did i mention cheap was another rule?) and better way to do this?

Keep your eye open for someone trying to get rid of an old fiberglass one who wants to replace it with a fancier one, and needs to have someone haul the old one away.

I remember a gas or diesel fired immersion heater from my army days. If you could find one, that would be good for heating up the hot-tub.

 

[Sponsor]

 

[Wet_Boots]

Ever wonder why folks don't keep their (outdoor) swimming pool is use over the winter? Heated up and ready to go? "Cheap" and "Heated outdoor pool" (even a small one) are mutually exclusive. ~ Look for a PBS program on duplicating an old Roman bath house, using ancient construction techniques.

 

[hj]

tub

What good would a "hot" tub with 3' of frozen water above 6" of near freezing water be? ANY gas line to a remote location would be underground, but what does that have to do with heating the tub? A customer had a 30 gallon propane water heater, then he installed a swimming pool with a heater. The propane company brought out a tank the size of a mini railroad car and fired up the heater. The pool was nice and warm and the next day the propane people were back. He asked them why they were there and they told him, "because the tank is empty". He turned the pool heater off and just used propane for the water heater. For the couple of years the company came out periodically to see if the tank was light enough to move because they had other customers

 

[Leejosepho]

Anybody up to the challenge of coming up with a CHEAP (did i mention cheap was another rule?) and better way to do this?

How he will keep it warm and sanitary is surely going to be a huge challenge, but he might begin with a relatively inexpensive poly tank/tub from a place like TSC (Tractor Supply Company). I got my 8' round pool there for less than $200.00 a few years ago, and at least at that time they also had a nice hot-tub shape for about the same price.

Tell you dad I also like to think outside the box, but remind him that we free-thinkers also do occasionally need to remain inside the fence!

 

[Geniescience]

BTUs, kWHs, energy units

very funny. The dilemma is well designed.

Heat transfer, heating Mother Earth, rate of heat transfer, rate of heat loss.

Slowing down the heat loss, insulating. A big foam cup.

Putting foundations under this insulated vessel in a big pond.

If you hide it a bit, by having its sides only come up to the surface but not stick up through the surface, then how do you prevent relatively warmer water (i.e. light density water) from sliding into the rest of the pond?

Regardless of insulation, heat will escape fast enough to cost you roughly $1000 per year give or take 500. Even if you put a hot tub cover over it.


David

 

[Leejosepho]

Heat transfer, heating Mother Earth, rate of heat transfer, rate of heat loss.

Slowing down the heat loss, insulating. A big foam cup.

Putting foundations under this insulated vessel ...

Maybe you can help me here:

I have enough heating wire to heat a round, concrete pad for my 8' poly pool, and I plan to place that pool within a patio deck (built around it) that will eventually be enclosed on the back wall of our house.

How should I insulate and pour that pad?

 

[Geniescience]

Wedi is most of the solution

first you ensure structure of foundations; not my input here.

FYI, foam insulation can go underneath concrete slabs too. Foam. If you research this well, you will feel comfortable with a slab sitting on a heat break (foam) which prevents the slab from automatically "adopting" the same temperature as the ground under it. If your ground is dry, or wet, this has a big impact on slab heat loss.

Then i would install 2" Wedi (it's foam) or more, on top of the slab, using thinset as the cement glue to attach it to the slab. I would call Wedi too before doing anything, and tell them about the pool and the height of water. I might opt for spray foam after researching this, either with or without the Wedi. I might opt for spray foam as a first layer and as a glue, and then smoosh the Wedi down onto it. Wedi is my first choice to be the top layer of the insulation, because it is covered with a thin layer of fiberglass and cement, making it ready for thinset. (One can also thinset on raw foam...)

Then i would thinset the heat wires onto the Wedi surface.

I have read on the web that the foam inside the Wedi foam slabs is a high tech product made by Dow Corning, a joint venture subsidiary of both Owens Corning and Dow Chemical, and this foam is sold to Wedi and to ten or twenty of its competitors. For now the market in Europe is where the action is, as North American distribution keeps a wait and see approach since no immediate action is require to "cut off at the pass" anyone else doing anything else that would threaten their grip on the market.

David

 

[Bob NH]

Heat transfer considerations make heating the water the best solution. Any other solution causes more heat loss to the environment.

Put the heat in the water and then put as much insulation around it as you can.

The tub should be covered tightly when not in use to prevent evaporation. Every pound of water evaporated carries away 1000 BTUs. If you put some cetyl alcohol in the water it will form a molecular layer on the top which will retard evaporation. That is the function of those plastic chemical-containing fish that they put in some pools.

 

[Phil H2]

. . . yes he is crazy. . .

4. figures he can run gas line under ground and heat tub from below.
5. is considering using heaviest possible sheet metal he can get for tub, with wooden benches to sit upon.

Is he considering putting a propane burner directly under the hot tub like a pot on a stove

 

[IleanasColors]

Yes Phil2,
I believe he plans on doing just that!