Replies

1. 
   Tim_H | Mar 19, 2000 05:10am | #8

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   David
   was the hazmat at the wendys some of their chilli that spilled?
   neat ideas about portable hot tubs. just one question, are the car radiators used? i know that moonshiners that use radiators don't get much repeat buisness. yea i know i'm not supposed to drink out of a hot tub , but what about skin contact? what if my dog can't find a toilet and is forced to drink from the tub?
   i have some wonderful memories from soaking in a wood fired (snorkal) tub at 35 below and watching the norther light show.

   tim H north of DAvid in anchorage

2. 
   Guest_ | Mar 19, 2000 09:34am | #9

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   Tim: If you're in Anchorage, you probably know the Wendy's of which I spoke. While the old underground tanks put petroleum in the groundwater, the much greater health problem 2 months ago was airborne, particulate lead. Of the .38 caliber variety. For all the known cancinogens I've cleaned up at various West Coast sites, a Kevlar vest would still be more helpful than a carbon filter. 6 dead at a Sacramento site, 2 in Fresno and now one in Anchorage. "Can't we all just get along?" -R. King

   Yes, dissolved lead is a possibility, particularly in acidic water. I wouldn't install a radiator-powered hot tub in a home, but these hot tubs are in use for a few hours before the water is dumped out. And remember, all pre-1985 houses with copper pipe have lead joints, just like that radiator. -David

1. 
   Guest_ | Mar 19, 2000 08:03pm | #10

   *Steve: The guys in Alaska's "banana belt" probably still don't have to worry about the humidity you have to contend with. So, I would make a trip to a couple local athletic clubs. Look at their steam rooms and apply to your situation. Personally, I've seen two or three installations like what you describe. None of them had adequate barrier between the house and the tub room. After a few years lots of rot and general slime, not a very satisfactory condition. On the other hand, in your climate you may be able to put some power ventilation in the area that will solve most of the problems.

1. 
   Guest_ | Mar 19, 2000 11:13pm | #12

   *Steve Your note reminds me of a job i did about 15 years ago. We actually put the tub in a townhouse dining room. We set a liner under the tub and added a large vent fan, I mean very large. Will check my files in the next day or so and contact the owner to see how the set up is going, Or went. Will let You know the results Skip

3. 
   Guest_ | Mar 19, 2000 11:13pm | #11

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   A client has a hot tub on a 14' x 24' screen porch, and wishes for me to enclose the porch as a fully finished sun room. The hot tub will remain. The sun room will have a ceramic tile floor, will be heated and air conditioned, and will be fully enclosed with operable windows and a patio door to the deck. A sliding patio door will remain between the sun room and the main body of the house. The existing screen porch has a finished, insulated ceiling with "traditional" ventilation (i.e., soffit and gable end vents). Climate is Tidewater Virginia.

   I can see some humidity issues here, and would appreciate feedback as to whether this project is one I should pursue (and if so, any tips).

   Thanks in advance, Steve

1. 
   Guest_ | Mar 16, 2000 04:13am | #1

   *Steve: I see some humidity issues as well. They can be reduced by creating a tight cover for the top of the hot tub. I've found two layers work better than one. A closely trimmed layer of bubble-pack (the stiffer than packing material blue stuff) floating on the water and a rigid foam insulated cover with a perimeter gasket material to seal to the top of the hot tub. The rigid cover does most of the job, but the bubble-pack stuff helps because without it you get warm, very moist air just under the rigid cover - so any little defects in the rigid cover lose more moisture. There was a FHB article maybe 5 years ago that showed a turnable support for the hot tub cover - the thing must have been heavy. I would epoxy 1/8 mahogney plywood onto both sides of 2" blue foam and trim the edges in 1/4" or 3/8 hardwood plywood. Great insulation, really stiff, really light. Coat the bottom in epoxy for waterproofing and coat the top however you like. Back up the joints with a little fiberglass tape. I take my kayaks and paddles of that construction into iceberg infested water up here, land them on rocky beaches, and they hold up great. If you want the cover to be able to support a couple of adults, do what the surfboard builders do - put a few stringers of 1/8" or 1/4" plywood vertically within the foam.Can you spec radiant heat in that tile floor? Any spill will evaporate really quickly (less slip hazard) and the floor will be nice and warm to the barefooted naked bodies running around.You'll need some way to move air when the tub is in use. 20 square feet of 104F (40C) water and 4 to 10 sweating heavy breathers will fog the windows really quick. Once people have been a few minutes a cool breeze is very welcome, so consider a fan of some sort and cracking one of those operable windows. Windows on opposite sides might suffice if you've usually got prevailing breezes. If not, and you want to avoid the fan, have one window low and one window high on opposite corners of the room. If the outside air is colder (or warmer) you'll get a chimney effect (or negative chimney effect) to move air through the room.You'd better have double-pane windows on that sun space. And include a caveat in your contract that there WILL be high humidity in that room and that the homeowner must 1) actively work to reduce that (keep the cover in place and maintained), and 2) accpet that despite everyone's best efforts, there will still be more moisture in this room than desirable. Unless you go for a dedicated HRV and humidistat (hygrometer) controlled ventilation.Rule of thumb: a hot tub of D diameter (in feet) holds about D^2/2 very friendly people/Unitarians, D sociable people/Methodists, or 4 people in bathing suits/Catholics. I've had 17 naked backpackers in my 6-foot tub, but there wasn't water left when they all got out. -David Kenai, Alaska

1. 
   Guest_ | Mar 17, 2000 02:27am | #2

   *Nice to hear from you, David. Hope springtime is just around the corner for you up there.We have done two major projects for this client, and feel obliged to follow up on this one.The hot tub has a (very nice) factory cover, and the tub will see limited use since the client (really) is an ex-minister and hosts few naked backpackers. The cover is certainly not air-tight, and I can imagine the warm, moist air wafting out of it on a continuous basis... something like the vaporizer we used for our kids when they were ill. Perhaps if I tried temporary wrapping with poly around what is now the screen porch, I could demonstrate to the client what problems he will face.Thanks for your input, Steve

1. 
   Guest_ | Mar 17, 2000 08:15am | #3

   *If the factory cover is nice but imperfect, how about backing it up with a something like a hot tub shower cap (or hot tub condom, depending on your tastes)? A few yards of the lightest, waterproofed (urethane coated) nylon with an elastic band around the edge. Stretch it over the tub and then put the factory cover in place. Any backpacking tent repair shop could stitch that up for you. Check the waterproofness of fabrics by trying to breath through them while the fabric is tight to your open lips. If you can suck the fabric in without pulling air through, it is fairly waterproof. While not as visually pleasing as installing the top of the tub flush to the floor, installing the top of the tub a foot above the floor level is MUCH more functional and safer. Instead of trying to step down 15-18" to the seat (that's a tall step), you step over the tub rim to a seat that is about the same height as the floor. Alternately, if the tub rests on the floor, shorter legged people have trouble stepping in, unless there's a bench around at least one side. I prefer having a bench (or the floor a foot below the rim) on one side and a deck to the top of the tub on the other side. Then there's a place to sit with your legs dangling in when you get too warm.I've built several hot tubs from scratch, but the ones that got the most attention were the car-camping, backpacking, and snow camping versions. (Similar but with different weight limitations and heat outputs). -David

1. 
   Tim_H | Mar 18, 2000 01:29am | #4

   *please explain how you deal with the back-packing tub. which poses a bigger problem- the weight or the size (and i always complain about my sleeping bag being to big). while yer at it could you also enlighten me as to the car and snow models.hey are you the guy with the bad hambuger ads?

2. 
   Guest_ | Mar 18, 2000 03:13am | #5

   *Tim: I think it's unfortunate that Dave Thomas, father of Wendy, has been hawking his hamburgers personally. It has made me a little more insistent on "David" as opposed to "Dave". It is also unfortunate that it doesn't get me any free burgers. I was working at a Wendy's (because it was built on a toxic waste site - I'm an environmental engineer) and they thought I was kidding them. Made me show them me I.D.The backpacking hot tub (met my wife six years ago on its maiden voyage) is the lightest one, about 80 pounds total - other people help me carry it in. The tub consists of 6- to 10-mil polyethylene sheeting lining a hole in the ground. Easiest in a sand dune on the beach. The water source is a garden hose used to tap a stream uphill of the tub. The water then flows by gravity thru an automotive radiator (as a heat exchanger) with 6 backpacking stoves under it.While this is the lightest setup, it takes 4-5 hours to fill it because at 60,000 btu/hour gross and maybe 40,000 btu/hour net, you can't have a fast flow of water. If the water doesn't go in hot enough or you are trying to keep it warm, manual recirculation with 5-gallon buckets is necessary.The car-camping version adds a plywood frame - ten panels of 1/4" plywood each 18" wide by 18" tall and hinged by threading 1/4" thru holes on the edges or by gluing and stapling 4" nylon strap (trucker's straps) as a piano hinge. This 5-foot diameter frame is lined with plastic after a foot well has been dug, if possible. A 12-volt circulation pump move water from the tub to the radiator and back again. But the burner is now a 125,000 btu/hour propane cooker. Takes about 2 hours to come to temperature. With the higher heat output, a flame spreader of a steel plate or a flat rock helps avoid boiling hot spots within the radiator. Or a lower loop of 1/2 pipe with water circulating work very well. The automotive radiator is very efficient. You can look thru it at the red-hot burner, but place your hand on top of it. 2-core, smaller radiators (small Toyotas and Datsuns) work better than 4-core larger radiators from Cadillacs) The large size just overhangs the burner and wastes heat. The third and fourth cores don't capture much heat at all, they just steal flow from the lower two cores where it needs to be to keep the radiator cool.The snow camping version is smaller and meaner to get to temperature faster. The plywood frame is 4-foot in diameter (holds 6 friendly, naked people) and is lined with ensolite pads. The pump is a 2-stroke, 1-hp, 16-pound gasoline pump that move so much water thru the radiator that the propane burner can be run full-throttle. Comes to temperature in 40 minutes and even at idle, adds enough heat so we throw shovelful of snow in to keep the water down to 104-105F. Haven't tried it, but forming the tub in a snow bank should work well if lined completely with ensolite pads (they being lighter than plywood.As you go to larger burners and pumps, garden hose gets a little skimpy. Full-sized (not 1/2") is definitely needed, but short lengths of 1-inch tubing works much better.

3. 
   Guest_ | Mar 18, 2000 04:09pm | #6

   *David, thanks for your replies. Your hot tub projects are definitely more interesting than mine. Glad to hear you can fit "6 friendly, naked people" into your snow camping version. Sure wouldn't want to have 6 UNfriendly, naked people, though!I notice also that you have wisely avoided development of a "desert camping hot tub" that would involve portaging hundreds of gallons of water to the camp site. Knowing you, however, I can imagine you would find some way to condense moisture on the underside of a tarp and eventually fill the tub despite the desert environment... then you'd use the tarp in some way as a solar collector over the tub, right? The tarp could additionally serve as (a) a sunscreen, when needed, and (b) a "hot tub condom" to keep out scorpions, gila monsters and such.With appreciation, Steve

4. 
   Guest_ | Mar 18, 2000 05:52pm | #7

   *Steve: For a desert hot tub, I really like the natural hot springs in Saline Valley, NW of, and now part of Death Valley National Park, California. All winter long there's an ever chnging community of hippies (some originals from the 60's and some posers) who soak, share meals, and maintain a lending library. The military still practices there and I don't why they call it a steath plane. When supersonic, it's pretty obvious. Even if you're deaf, you can just look up and see a large very black plane.Hot Creek in Owen's Valley in California is also kind of interesting but the volunteer-improved natural hot-springs a few miles to the east and northeast are nicer and more private. In the winter, at 10F, you can lift your sweaty hair in the air for a minute and freeze various "hair horns" into place. -David