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Getting in hot water

Sunroom diagram

After some brainstorming (and a lot of good thoughts from your comments on our sunroom and hot water posts), Mark and I have decided that:

  • The sunroom is a lower priority than hot water, and may wait until another year.  Part of this reasoning is based on the fact that Mark actually doesn't consider it a hardship to wash up outside in the winter --- I thought he did.  (Personally, I'm pretty content with our current bathing setup, although I might like to lounge in a real bathtub some days.)  That makes setting up a bathtub and shower much easier since we can just put it on the other side of the wall from the kitchen sink, allowing us to easily plumb directly into the graywater system and to get hot and cold water with minimal fuss.  (As a side note, I also changed my mind about where the potential sunroom should go --- you can see my current thoughts in the diagram at the top of this post.)
  • The solar hot water system and the backup electric hot water system don't necessarily need to connect together.  Since we use hot water almost entirely in the late afternoon, a batch-type solar hot water system could serve as collector and reservoir during the warm months.  I still haven't decided whether the best option is the trailer's old hot water heater, painted black and placed inside a glass-fronted box (would the insulation keep the tank from soaking up the sun's rays?) or a couple of hoses inside a similar box (or just up on the trailer roof).  Without the complication of a thermosyphon system, though, it definitely feels simple enough to build ourselves.
  • Water heaterOur best option for conventional hot water during the winter is probably a 19-gallon tank, which we'd turn on a few minutes before using just like Tom suggested they do in Mexico.  A point-of-use unit could be good, but has two potential problems in our unconventional circumstances --- it would need fancy wiring since it draws so much juice all at once, and it might not work with our low water pressure (we get 1 gpm, or possibly less, depending on how full our tank is).  You'll also notice that I increased the size of the reservoir we're looking at since I forgot that we currently use boiling water to mitigate water temperature, while a hot water heater (even set on high) is only going to raise the temperature of the water to 150 degrees Fahrenheit.  As such, my calculations suggest that we'd need a 19-gallon tank in the winter to raise water from around 40 degrees to 105 degrees to fill a 35 gallon tub.  Presumably, we'll learn to tweak how long we wait between turning on the heater and using the water so that we don't waste energy heating too much water during lower-water-use projects like showering and dishes.

Mark tells me we usually see a very slight lull in our workload in late July, so hopefully we'll have time to set up our bathing chamber, hot water heater, and solar hot water system then.  If not, it will definitely be our winter infrastructure-improvement project.  Now I'm off to research whether low-flow faucets and shower heads will work with already very low water pressure....

Our chicken waterer keeps hens happy with clean water.


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If you use an old water heater tank, you need to remove the insulation and outside cover.
Comment by Errol Sun Jun 30 08:54:10 2013

A solar collector won't be of use in the winter. Here at 51°26' N they've been in use for some time now. They tend to gather useful heat from April through to September. I've seen figures ranging from 10 MJ/day on a sunny day in April to 30 MJ/day on a sunny day in July. In these parts they tend to be used on combination with a large (500 L, 130 gallon) buffer tank to capture as much as possible on a sunny day and to account for less sunny days.

An electric boiler would be much more reliable in winter (as long as you have power) than a solar collector. Check with the manufacturer though if it would be suitable for a low-pressure water unfiltered supply like yours. You wouldn't want the tempaterure and pressure sensors to foul up. And especially not the pressure relief valve. Google for "boiler rocket". :-)

But seeing as you have a source of firewood, e.g. a water mantle around the stovepipe might be a goos source of hot water in the winter.

"would the insulation keep the tank from soaking up the sun's rays?"

Yes, definitely. But if you remove the insulation, the tank is more prone to losing heat as the sun goes away. And unlike a solar collector, a tank has a dismal area/volume ratio, meaning that it won't catch a lot of sun to begin with, nor wil it heat up the water quickly.

"the complication of a thermosyphon system"

Huh? A thermosiphon is one of the simplest heating devices there is. A typical solar collector setup we see here is much more complicated.

Comment by Roland_Smith Sun Jun 30 13:51:06 2013

The units in Mexico were smaller than 19 gal. I've searched for a long time and can't find anything.I'm thinking 6 or 10 gallons. And, I am sure they were 110 Volts single element.

If you've done the math, I can't argue with you about what you need though. In Mexico, it was shower only.

In my old hot tub, I find I can barely tolerate 105 degree water. 101 or 102 is most relaxing for a good soak. That's measured with a thermometer, not the indicated setting on the thermostat.

Comment by tom Sun Jun 30 16:04:36 2013
We have solar thermal hot water that was set up to pre-heat the water in an electric tank. We switched out the 50 gallon tank for a 19 gallon tank which runs on 120 instead of 240 volts and we leave the electric shut off.. When we don't have solar hot water, we turn on the electric (usually only a problem in Dec & Jan here in the NC mtns) - 19 gallons is plenty to take a couple of showers but I'm not sure it's enough to take a hot bath. It takes about 45 minutes to heat from around 80 degrees to 120 degrees so you have to plan ahead but it has worked great for us, in conjunction with the solar.
Comment by Katherine Sun Jun 30 22:23:42 2013

I'm not sure how you feel about propane, but the tankless hot water heater works great for us. I think you can also get en electric version. It only comes on when you turn on the water. We use this for an outdoor shower at the farm and it works great. The only issue would be figuring out how to keep it from freezing in the winter. http://www.amazon.com/Camp-Chef-Triton-Water-Heater/dp/B00A0M6HDM/ref=pd_sim_sbs_hi_1

Comment by Jackie Tue Jul 2 08:13:50 2013

I finally found a link to a picture of the outside of my apartment in Oaxaca, showing the small water heaters. http://tom2mexico.blog.com/page/5/

I tried to past the picture here, but couldn't. Must be text only. the heaters were real small though. The door is the same size as in USA for scale.

Of course, it was for shower only. SO the size in Mexico may be moot.

Comment by Tom Fri Jul 5 17:59:33 2013

One very unique homestead, $1,500 per acre, the opportunity of a lifetime