Is weight an issue for heat pads under water tank?

[csulli]

Hey everyone,

Just trying to safeguard my 62ga fresh water tank under the bus from freezing. I know the heating pads should be stuck to the underside of the tank, to be in direct contact with the water no matter the levels in the tank (unless it's empty in which case we wouldn't have the heating pads on at all). We have our tank sitting on a piece of 1/2in plywood for protection from road debris, so the heating pads would sit in between the plywood and the tank.

Does anyone think there will be a problem with having the weight of the tank pressing directly on the heating pads?

Thanks!

[MorningOwl]

I have the same question. Did you ever find out?

[Rwnielsen]

Heating pads that I've dealt with are usually just back and forth runs of Nichole or other resistance wire. Pressure as you describe shouldn't bother them at all

[Veloc]

In my mind, the bigger problem would be having a resistance heater pushed into flammable plywood by 500ish pounds of water and tank. Anything goes wrong and the plywould could go up, and if it did the fire would reach the rest of the bus before it burned through the tank. Others can correct me if I'm wrong, but I'm thinking you will want some fireproof insulation between the heater and the plywood. Insulation would be a good idea anyway, to keep the heat where it should be.

[headdownlow0624]

Originally Posted by Veloc

In my mind, the bigger problem would be having a resistance heater pushed into flammable plywood by 500ish pounds of water and tank. Anything goes wrong and the plywould could go up, and if it did the fire would reach the rest of the bus before it burned through the tank. Others can correct me if I'm wrong, but I'm thinking you will want some fireproof insulation between the heater and the plywood. Insulation would be a good idea anyway, to keep the heat where it should be.

That's a very good point! This one will take more research. Most of the tank heaters I've been shopping for cut off around 60°F (at the pad). This is significantly below the ignition point of wood, which Google claims the low end to be just over 200°F when constantly exposed to a heat source over multiple years. (Ref= https://www.warrenforensics.com/wp-c...tion_Wood-.pdf )

If the wood is not constantly exposed to heat, it won't ignite until closer to 500°F. I'd consider this low risk, but more questions... is the plywood getting heated by any other source? Exhaust pipes maybe?

What does the manufacturer of the heat pad say specifically about compressive strength? I'd be more worried about the weight of the tank slowly causing an "open circuit" in the pad, an issue you may not realize until the tank is already frozen. Maybe distribute the weight evenly with a bridge of leftover small diameter PEX pipes? Or some type of spacers, maybe Nylon? Any air gap between your tank and plywood will only help insulate it (If it's mostly enclosed). Not trying to hijack this thread, but I also have not decided on a solution yet. I see the OP is from March, any updates?

[turf]

i've used a few of the pad heaters on my bus and this is my 2 cents.

the pad heaters are short term solutions, if you get 2 years service out of them, you've exceeded my experience.

for that reason, i would not install them captive underneath a tank.

even brand new, maybe 2 or 3 of the 8 or so pads i have purchase from etrailer did not work on arrival.

read the description carefully, some have a tstat built in, some do not.

my fresh tank is inside and heated by the bus furnace. my waste tank is outside exposed and needs to be kept liquid so i can dump in the winter time.

the pads help thaw the tank, to a certain extent. if it gets colder than about 0, they wont thaw anymore. you'll need help from mother nature.

in the waste tank i use ice melt salt too, but thats not going to help a fresh tank.

generally, the tank is the last thing to freeze. any plastic fitting or brass elbow is probably more susceptable to damage than a tank.

when i lived in the mountains, i used a hammer on the side of the tank to judge whether or not to turn on the heat pads. 2 days of melt time made sure i could drain the tank at the dump.

[Jeff2010]

I’m not seeing anything around the use of tank heaters inside the tank itself?? is the use of agricultural tank heaters an option? Not trying to keep the water warm…just not freezing…also need to find one that fits into a tank