Tank insulation

[cencerrita]

Has anyone used spay foam insulation on their grey and black water tanks? Does it stick well on plastic tanks?.
Thinking of doing the bottom and some sides accessible as apart from cold wind overnight when driving the chill factor will be low and not always possible to have empty.

[dave17352]

jjrbus wrote:
When I did a bus conversion I put waterbed heaters under the tanks. They require 3 inch of water in tanks at all times.

Very good point if the OP puts heaters on you definitely need to have the tanks 20 to 30 percent full keep the electric heaters on. Otherwise u might ruin the heaters.

[jjrbus]

When I did a bus conversion I put waterbed heaters under the tanks. They require 3 inch of water in tanks at all times.

[cencerrita]

Thanks for all the advice

[TurnThePage]

It's easier to glue foam board to the tanks, then spray foam the corners and gaps. Might not be a bad idea to install tank heaters first.

[dave17352]

I think if the tanks were cleaned well the spray foam would stick. Maybe afterwords you could wrap the tank with a heavy duty exterior fabric to help hold it in place. The wind may get the tank to the temperature outside quicker but will have nothing to do with freezing, If it is above 32 nothing is going to freeze no matter what. I believe if you insulate the exposed side completely and you have the top of the tanks exposed to the heat of the cabin you would help pretty substantially. You can buy a larger size tank of that spray foam from some big box stores that is used for insulating rim joists in construction. The stuff has a great R value and is some sticky poop. Also you could dump a little rock salt in the tanks as this will lower the freezing temp. We did that for years when we went ski camping. But if your talking real cold like 25 and below you better look into some tank heaters as another poster said. All though rock salt will work pretty darn good. JMHO

[westend]

Since there is very little mass of heat inside a water tank or waste tank and the tank may be located in an area at ambient temps, insulation will only slow the freezing process, not eliminate it. At cold temps without supplementary heat, the insulation will eventually reach ambient temperature, as will the tank.
I think the OP may be better served by installing tank heaters. They direct heat onto the tank surface and that heats anything inside the tank. Insulation between the tank heater and the outdoors is a good idea.

[profdant139]

Tanks that sit still will freeze overnight if it gets cold enough. Please don't ask me how I know this fact. While you are driving, it is less likely to freeze.

Folks have used a variety of methods to keep tanks from freezing. Spray foam helps (but is messy and expensive). My trailer has a layer of pink fiberglass, with a black vinyl sheet under it. I added Reflectix to the tanks -- it might help, but the R Value is fairly low.

Some folks have used sheets of styrofoam, supported by stringers.

[Calicajun]

corvettekent wrote:
Moving water does not freeze.

Is that why rivers and water falls never freeze? 🙂

[corvettekent]

Moving water does not freeze.