Onboard air, water tanks.

[gwbuild]

Originally Posted by 1der

Nice tanks and a great price.

Re: roof mounted water tank and solar heating - not recommended.

Water storage on roof - 40 to 64 lbs of sloshing water will be felt. The water “pressure” will be gravity feed, filling the roof mounted tank is a pita.

Re heating via solar on the black painted tank - when the tank is 100% full and stationary you will heat up the water in the top 10% the tank, the bottom will not heat without introducing some circulation which will only make it take longer to heat water as it will now be exposed to the colder bottom of the tank which is pretty much ambient as it is in the shade.

Cold water sinks (or stays at the bottom of a vessel if heat is applied to the top) - I found this out with a PV solar panel fed electric element water heater I made up - literally (once) had steam at the top of a tank (and at the faucet) and luke warm at the bottom of the tank (took temperature with an infrared thermometer) and that was in a four gallon horizontal tank. This happened because the heating element was in the top 30% of the tank. Took a while (I am a wanna be engineer) to figure out what was going on when the 150 deg set thermostat would click off and the water coming out the tap would not be expected the hot. I repositioned the heating element to the bottom 30% which now created convection currents in the tank and it now works great ( as does the pressure release system which saved my van from a water heater explosion when it went to steam that one time)

I have found the best solar hot water heaters for the roof or rear box are the solar bag style water heaters which can get to scorching temps if left out all day. Easily filled and easy to place on the roof or hang from a ladder or tree and gravity is the water flow. But as far as black metal tanks on the roof for hot water - nope.

If you want your own proof, set one of your black tanks up on a couple of saw horses. Have your fill at the top and supply at the bottom. Try it with a 100% full and another time that is half full. I think you will find what I am describing.

Still wish I had a use hot one of those tanks!!

Thank you so much for the great information, you've probably saved me a lot of time and headache.

Maybe hang one next to the exhaust, keep the weight low in the van and pick up some residual heat.

[Cruzliife]

Hey I’m in mar vista myself! I live on Beethoven St. I have a Viar 2 gal set up inside my van but I’m itching to mount it under neath, I could maybe switch the tank out for one if yours. Any chance I can come by see what you’ve done.
Thx
Tito

[gwbuild]

Originally Posted by Cruzliife

Hey I’m in mar vista myself! I live on Beethoven St. I have a Viar 2 gal set up inside my van but I’m itching to mount it under neath, I could maybe switch the tank out for one if yours. Any chance I can come by see what you’ve done.
Thx
Tito

Hey Cruz, yeah walking distance for sure. I should be around the house Friday through Sunday, or not very far, if you'd like to come by, PM me and I'll get you my info.
I've got five tanks left if you need one.