Wanted: Custom sewn cover for 10 gal Roadshower

[VanWaLife]

So just kind of spitballing here...pretty bummed that freezing temps can destroy the Roadshower. I've given some thought to solving this problem, and have a two-pronged approach in mind: attach a 12v electric heat pad to the Roadshower, and sew up an insulated cover for it.

As far as the heat pad goes, this is what I'm looking at:

Silicone Rubber Heater, 1" x 1", 12V, 5W, 6" leads

Silicone Rubber Heater, 1" x 1", 12V, 5W, 6" leads, available for online ordering from O.E.M. Heaters.

www.oemheaters.com

As far as the cover goes, I don't have any sewing skills. But basically I'm thinking a big tube shaped cover with a slit all the way down one long side, with velcro on either side of the slit. There would be a few velcro closure pieces to go between crossbars. Possibly holes with velcro flaps for the fill and charging ports. As far as cover material, I'm thinking space blanket type shell with an inner fabric insulation layer.

I think this is a pretty good idea, probably marketable to a great many Roadshower owners, maybe Yakima. The cover may be enough without the heater for a lot of situations, not sure how well the heater would work in lower temps.

So if you got sewing skills, especially in the PNW, let me know if this is a project you want to take on. I just want a cover, don't have any interest in commercialization of the idea myself.

If you have a Roadshower and also have considered this problem, let us know what your thoughts are, and what you think of this idea, and whether you'd be in the market for an insulated cover for your Roadshower.

 

[llamalander]

5 watts is going to take a long time to heat 10 gallons of water in an aluminum tube- about 25 hours to raise it 5º, assuming no heat loss from the tank- perfect insulation.
If the temp drops below freezing, it may add a few minutes to the freezing process, but not much more. Insulation will add some minutes and reduce the loss to wind, but not as much as you need.
Even if you fill it with boiling water, it will lose that heat in just a few hours on your roof in a freezing night.
Keeping it inside the heated portion of the vehicle in cold weather may be a better plan, even if it is kinda big and weighs over 100lbs.

 

[kwill]

Gotta agree with llamalander--no way 5W is going to help much. A better approach might be to drill a hole and insert a heating element. This one is 300W: https://www.amazon.com/DERNORD-Imme...ocphy=9028249&hvtargid=pla-323324380212&psc=1

 

[VanWaLife]

Seems presumptive to claim there's no way this will work without basic information like outside temp, water temp, r-value, etc, but you guys are certainly entitled to your opinions.

 

[kwill]

Seems presumptive to claim there's no way this will work without basic information like outside temp, water temp, r-value, etc, but you guys are certainly entitled to your opinions.

It's not presumptive; it's math. Heating 10 gallons of near freezing water just 5 degrees with 5w takes almost 25 hours. If the water is significantly colder than 32 degrees then I don't think you can ever get there.

 

[llamalander]

Physics is the law... Everything else is just a suggestion.

You laid out the situation above when you weren't asking for anyone's opinion.
Outside temp will be 32º or less if you are concerned about freezing.
The energy required to heat water is a constant, the max amount of water is a constant.
If your Roadshower can raise the temp of 50-60º water to 100-110º water in a few hours, it will loose that heat just as quickly, quicker still in any wind.
The R-value of an aluminum tube designed to absorb (and thus radiate) heat is zero.
No insulation exists that could be sewn into fabric that exceeds R-20/inch, most is 20% of that...
Insulation slows the transfer of heat, and that rate changes (for the worse) as the difference in temp between the outside and the inside grows.
5 watts is a very small amount of heat. A 1500 watt electric kettle will need 4-5 minutes to boil tap water, 5 watts would take about 4550 minutes to do the same thing.

Presuming all of that, it is safe to point out on the internet that the present proposition is probably unlikely to be worth the price of prototyping.

Looking at the problem critically, what is likely to be damaged by freezing?
The air-valve, the pressure cap and the hose spigot are the likely victims, the tank itself only if the expanding water will burst it.
If you wrapped the tank in cloth+insulation and opened the fill cap on a less-than full tank, you may prevent the worst of the damage.
If you spent that 5 watts or something equally minimal agitating the tank, you could probably prolong a hard freeze much longer than with a small heating element.
Knowing how cold your setup can get before risking damage would let you choose to keep the water or dump it on a cold night.
That might be worth investigating in something less expensive than a $600 water tank.

 

[DaveInDenver]

It's not presumptive; it's math. Heating 10 gallons of near freezing water just 5 degrees with 5w takes almost 25 hours. If the water is significantly colder than 32 degrees then I don't think you can ever get there.

In this house we obey the laws of thermodynamics!

It requires 24 watt-hours to change 10 gallons of water by 1°F, so a 5 watt heater probably can't keep this tank above the ambient temperature as it may be losing heat faster than you're putting back in if the air is cold enough for long enough.

The tank's transfer efficiency and the added insulation does play a factor in slowing down heat loss in the OP's theory so that's an unknown. Also coloring it black and having the Sun fall upon it would help. Although this won't be magic, on a long enough time scale the system will reach equilibrium.

So I'd prefer more than 5 watts. For comparison those all weather dog bowls use a 60 watt heater to keep 1.5 gallons from freezing. Of course they are fully exposed and work down into sub-zero air temperature so it's not completely apples-to-squirrels.

 

[VanWaLife]

OK well I went down the rabbit hole and figured I'd turn this thread into a write up of what I did. I started with a 12' long chunk of 8" ballistic nylon with velcro for about $170 (ouch), and a 50' roll of 24" foil backed insulation for $80 (ouch again).

Dura-Wrap Harsh Environment Seal - 8" Black

Even large wire bundles, multiple pipes and hoses, and piles of tubing can fit snugly into and out of this easy to use 6 inch Dura-Wrap Woven Nylon Sleeving.

www.wirecare.com

The sizes work out well so the insulation lays over the nylon without interfering with the velcro, and the nylon fits around the roadshower nicely laminated with two layers of insulation. I trimmed the nylon to fit around my roadshower supports, cauterized the cuts, and cut two layers of the insulation to match. Next I tried gluing the layers together, with the foil facing out using liquid nails Fuze-It:

The foil facing stuck to the nylon pretty well, but there was no gluing the polyethylene insulation back to back; turns out polyethylene is very hard to glue. At this point I called around to some upholstery shops and found a guy who sewed the three layers together for $100 (seemed really reasonable). It turned out great in my opinion, much better than gluing.

I mostly gave up on the idea of using electricity to prevent freezing, mainly because I already had a propane water heater, which is a much less controversial way to heat up the water. I purchased a Milwaukee M18 transfer pump for $229 (very painful) to circulate the water through the water heater. I also found some round foam pieces to insulate the ends of the tank.

https://www.homedepot.com/p/Milwaukee-M18-18-Volt-1-4-HP-Lithium-Ion-Cordless-Transfer-Pump-Tool-Only-2771-20/300510172

I've tested the system over the past two nights with and without the jacket on the tank. I have hose bibs at either end of the roadshower, so I used both to circulate hater through the tank, and I discovered I had to start with the tank pressurized to avoid collapsing a hose, although it's possible this could be avoided by moving the pump elsewhere in the system.

I'm pretty happy with the results. Temps were pretty consistently around 35 degrees over the two twelve hour tests (8pm to 8am). Each night I heated the water in the tank up to about 90 degrees (took about 5 minutes and the better part of a 5ah M18 battery). With the jacket on, the water was about 60 degrees the next morning. Without the jacket water was close to air temp of 35 degrees. I have no doubt this system would prevent damage to the tank overnight probably well into the teens. It seems like it would be possible to make the system automatic with a thermostat controlled 12v pump, possibly even turn it into a hydronic heating system. But for now I'm happy not having to worry about my water system in freezing temps. Also using the water heater by itself is a little frustrating (especially for showers) as it can be a little finicky. This system allows me to heat the water in the tank up and avoid the delayed heat and misbehavior of the tankless water heater.
All told I'm into the cover and pump close to $600 (would be grounds for divorce, if I were married), almost the cost of the roadshower itself. This could be done much cheaper with the same result by skipping the nylon and just bungeeing insulation around the roadshower. The transfer pump is fairly useful outside of overlanding, so there's that. And I have some extra ballistic nylon, insulation, and 7" craft foam circles, so there's that too. We'll see if it really pencils out for me. If I end up using the beejeezus out of the truck when overnight temps dip into the teens, it will have been worth it. One other drawback: the cover is fairly bulky removed.