Wednesday, June 11, 2008

Hot Tub!

In my last post, I shared that we are parked right on the Snake River. In fact, the river is just 40 or 50 feet from our site. Interestingly, if we were dispersed camping, this spot would be considered "too close" to the water. But it's a developed site, and this is where they marked it. (Dispersed camping, BTW, is not allowed here, as is typical of Park Service managed property.)

One of the great things about this right-on-the-river spot is that we have the opportunity to use our "YachTub" portable hot tub. We spent an hour after our arrival between inflating it:

and getting the little electric pump set up down by the river. We carry 150' of water hose and 150' of extension cord for just this purpose (dispersed camping rules mandate camping at least 100' from water sources) , but we only needed a single hose here since we're so close to the water.

The pump is a small, general purpose unit we bought at Home Depot. Designed for draining water beds, cleaning up basement floods, and the like, it has about a 2.5gpm flow rate, depending on lift. It took about two hours to fill the tub, about 300 gallons or so.

The outside temperature has been in the 30s, but the water in the Snake is running at about 60° right now, as registered by our floating spa thermometer:

The tub is heated by our Webasto diesel-fired boiler, with which, at this writing, we're having some problems. So it's not surprising that we were not able to get the tub up to temperature last night. We had ridden our scooters over to Flagg Ranch for dinner, and so did not start the heating process until we returned (since the Webasto needs resetting every five minutes in its current state). Between the finicky Webasto and some known problems with our early-beta model tub control (we're promised a more robust production-model replacement, but getting around to swapping it has been low priority for us for, umm, three years now), we gave up about an hour into it.

Today is a different story
-- in spite of the bitter cold, we've been running the hot tub water (which is really murky -- the Snake is running high and muddy right now) through the heat exchanger all day while I fiddled with the Webasto fuel system.

We've needed the house heat anyway, so we're not really using that much additional diesel. At this writing the tub is up around 90°, from a starting point of about 57° (it dropped a few degrees over night), and I expect we'll have stew in another hour. With any luck, the pre-teen girl in the tent next door will be in for the night, and we'll zip outside in just our towels (Odyssey is between the tub and their site, anyway). In the snow, if current conditions continue.

Postscript: I wrote all the above yesterday, and it's taken us until now to get it all in order and all the photos uploaded. I'm happy to report that we had a great soak last night, with the tub right around 100° (102° would have been nice, but with the air temperature in the 30s, the system struggles with the heat losses just in the hoses and pumps). And yes, it did snow on us lightly, but we extended the awning, which kept it off our heads.

We covered the tub with a tarp when we were done, secured like a drumhead with a rope around the tub, and the water was still around 82° this morning when I checked -- not bad for a sub-freezing night. We're looking forward to another nice soak tonight, with somewhat less heat-up time required (and the Webasto, for unknown reasons, seems to be working normally today).

When we're done and ready to leave here, we'll use our hose to drain the tub right back into the Snake -- no muss, no fuss. Other than being just a few degrees warmer, the impact will be no different from having taken a swim (brrr!).


  1. Hi Sean,
    I have a suggestion for "testing & using" the wabasto until you are able to get it fixed correctly. Back when I was trucking, occassionally I would have a fuel problem with the reefer unit on my trailers. (sometimes it was an empty tank, and sometimes it would be something else! LOL!) But it only seemed to happen when I was on a "hot load" (meaning get there ASAP), so I kept a temporary fix in my tool box! I kept a roll of appropriate sized fuel line, several fittings a weighted fuel filter (fishing weights attached to the filter with hose clamps), and several clamps. I'd attach the filter on the long part of the hose and unroll enough to route to the truck fuel tank (with some safe slack of course) and drop it in the tank. Then I'd cover the openong of the tank with some plastic & duct tape. Then I'd duct tape the rest of the roll close to where it hooked up to the reefer units injection pump, & attach the loose end of the hose to the unit. Walla instant fuel to the reefer unit until I had the load delivered and had time to find and fix the problem! I'll bet yer "car quest source" could fix you right up with the same set up.After all you only use the wabasto while parked right? by leaving the hose on the roll it makes it easy to roll back up, for storage and re-use! Happy motoring, I'm headed into the scorcing heat of FL for a week! ;D BK ;D

  2. Oh SWEEEEEET! Magic Bus people, please come camp next to us, we'll be your best neighbors EVER!

  3. @busted knuckle: No place here to buy fuel hose -- I already tried. That will have to wait for our next major town, after Yellowstone.

    @liveworkdream: Hey, we did our best to try to hook up with you in Colorado! We did buy the 4-person tub, so we can have guests. But our tub is strictly "no suits" (unless there are minors involved)...

  4. Hot tub.

    Okay, now I've seen it all.


  5. @Raven:

    Not quite, because this is a G-rated website :-)

  6. Have you considered a solar based heating system for the hot tub?

    I've seen solar heated shower bags and this:

    Willing to brew up your own system?

  7. @mike -- While solar pool or spa heating systems are in use in some fixed dwellings, they are very large. Unlike those two or three gallon solar showers that you mentioned, it's just not feasible for us to use solar energy to heat our 350-gallon hot tub. The reason is simple physics:

    To heat just 300 gallons (how far we normally fill the tub) from 60° to 102° would require over 105,000 BTUs (one BTU is the amount of energy required to raise one pound of water one degree Fahrenheit, and a gallon of water weighs about 8.34 pounds).

    Now, on a perfectly clear day, at high noon, in the summer, with collectors aimed directly at the sun, you might see perhaps 300 BTU per square foot of incident solar energy. Even if you could make a 100% efficient collector, to heat the tub in, say, eight hours would require 44 square feet of collectors.

    Realistically, double that figure because you can't get midday sun for eight hours, no collector is 100% efficient, and conditions are seldom perfect, and now you're closer to 90 square feet of collectors. Even then, we'd have to keep aiming the collectors right at the sun -- otherwise, double it again: say 180 square feet. And then, we could only use the hot tub on perfectly sunny summer days, right at the end of the daylight, for only a few minutes.

    As soon as you start circulating water, especially with the temperatures in the 30s that we've had here, you start experiencing heat loss to the environment. Even with the cover on and no circulation, the tub has been dropping 20° over night -- call it ten hours, or 2° per hour.

    That translates to roughly 5,000 BTU/hr for our 300 gallons, just to keep up with the losses. That would add another ~60 square feet of collectors, which, again, would only work on a sunny day.

    Today is the first sunny day we've had since we arrived three days ago. So even with, say, 240 square feet of collectors, we would not have been able to use the tub at all until today.

    All of which is moot, since there is no place aboard Odyssey where we could store that many solar collectors, and they would weigh, conservatively, in the neighborhood of a ton (not counting the extra water to fill them). Nor could we find that much clear real estate to set them up in most places -- certainly not here in this camp site.

    By contrast, a single gallon of diesel fuel contains 139,000 BTUs -- more than enough to heat our tub from 60° to 102°. In practice, because of the way our system works (some of the heat goes elsewhere, such as making domestic hot water and heating the inside of the bus, and some is wasted in the combustion process), it takes three hours to heat the tub, using 1.2 gallons of diesel.

    Probably more than you wanted to know, but I hope that sufficiently explains why we are not considering brewing up a solar heating system.

    FWIW, all the spare real estate on the roof of the bus is occupied by solar panels -- the photovoltaic kind -- which supply part of our electricity requirements.


  8. Oops -- I meant to say "300 BTU per square foot per hour" when talking about incident solar energy.

    No way to edit comments on BlogSpot, or I would have just fixed it...

  9. Actually that *is* what I wanted to know. I knew that solar isn't very efficient, but it didn't expect to be that in-efficient.


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