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KYAirstream 11-12-2013 09:21 PM

Alternatives to RV heat pads for tanks
 
Just curious if anyone has experimented with lesser priced alternative methods to heating the fresh and black/grey tanks. Anyone try larger reptile heating pads, or materials like this....?

https://www.amazon.com/Hydrofarm-MT10...bxgy_lg_text_y

https://www.amazon.com/Flex-Watt-Heat...=pd_sim_misc_2

Protagonist 11-13-2013 06:37 AM

Quote:

Originally Posted by KYAirstream (Post 1379275)
Just curious if anyone has experimented with lesser priced alternative methods to heating the fresh and black/grey tanks. Anyone try larger reptile heating pads, or materials like this....?

Amazon.com: Hydrofarm MT10006 9-by-19-1/2-Inch Seedling Heat Mat: Patio, Lawn & Garden

Amazon.com: Flex Watt Heat Tape - Flex Watt Heat Tape 11" Wide Tape (110V) (20 Watts per foot): Pet Supplies

It appears that thermostats are sold separately, and you'd definitely want one for each heated tank, set to about 40F.

A heat pad is a heat pad is a heat pad, and they'll all work more-or-less the same way. The main thing is, are they waterproof? If you get condensation on the outside of your tanks, or a leak, you don't want an electrical short catching your heat pad on fire. Though admittedly a burning heat pad will keep your tanks warm for a while!:lol:

And how do you plan to fasten them in place? In order to work properly, they have to be on the bottom of the tank (so you're heating the liquid, not the air at the top of the tank) and they have to make contact over the entire bottom of the tank, not sag away from the tank. But at the same time they can't be crushed by tank hangers or you're back to that whole short-circuit issue.

Not saying you can't do it. Just giving you a few things to consider to help make sure it's done right.

My Interstate has heated fresh and gray tanks; the black tank is above floor level and doesn't need heat pads because the furnace does the work for that one. Be advised that heat pads are energy hogs; if you try to run them off the inverter, they'll drain your batteries stony dead in four hours or less; only use them on shore power!

Skater 11-13-2013 08:18 AM

Interesting idea. In addition to what Protag said, the 'real' tank heaters are a much higher wattage - for example this one is 164.4 watts for 12"x20", while the reptile heater link you gave is 20 watts per foot - so about 30 watts for the same square footage. My guess is they wouldn't work well enough - the heat has to go through the plastic and warm the liquid inside, while being in a cold environment itself...

It's one of those things - if it works, GREAT you've saved a bunch of money. If it falls short, well, that purpose-built tank heater probably would've been much cheaper than repairing/replacing the tanks might be.

Protagonist 11-13-2013 09:01 AM

Skater brings up an excellent point. You have to test the heaters with the tanks completely full. If the heat pads can heat a full tank, they can heat a partial tank just as well.

But if you test it and fail, you've got a ruptured (or at least leaking) tank that will have to be repaired or replaced, and a cold wet mess to clean up.

So get a heat pad for one tank, your largest, and fill it with clean water even if the largest tank is a waste tank. Even better, remove the tank from the airstream in order to install and test the heat pad, so that even if the tank ruptures it doesn't affect the trailer. If it doesn't work, you've only paid for one heat pad, not two or three, and the leaking tank is already out where it can be fixed or replaced easily.

If it does work, then you can reinstall the tank and the heat pad, and get pads for the other tanks that need them.

Skater 11-13-2013 09:46 AM

Though I have to say, looking again, those purpose built tank heaters are rather expensive. It's not so bad until you realize you need three of them... Hmm.

There's quite a few variables involved in figuring out what would be sufficient for a given camping experience - for example, if you knew you'd never camp below 0 degrees F, then in theory you could calculate how much energy you'd need to transfer to the water to keep it from freezing (assuming sitting still at a campsite, with a full tank). But you definitely lose heat to the plastic tank itself, and probably also lose heat to the air around the heater, and the belly pan, and I don't know how to figure all of that in. In short, it's going to be hard to figure out how much power you really need and whether the cheaper versions would be enough or not.

arodriguez60 11-13-2013 12:11 PM

have you thought about a waterbed heater? https://www.walmart.com/ip/Solid-Stat...eater/11018026

robwok 11-13-2013 12:29 PM

love this thread. About to instal my custom tanks here soon.

MySovereign 11-13-2013 01:04 PM

Quote:

Originally Posted by arodriguez60 (Post 1379535)

Great idea! However, there are WB heaters for "hardside" and "softside" waterbeds. Wonder which would be best for a black water tank?

Ditter 11-13-2013 02:03 PM

This may help with sizing wattage requirements
 
Since 1 watt hour will generate 3.412 BTU (1 BTU will raise 1 Lb. of water 1 deg. F). Therefore 1 gal of water weighs 8.35 which would require 2.44 watt hours to raise 1 deg. If you had a 50 gal fresh water tank you would need 122.3 watt heater to raise tank 1 deg. in 1 hour this would not include heat loss from outside.
Amp draw at 120 volt would be 122.3/120= 1.01 Amp

perryg114 11-13-2013 03:37 PM

Where are you camping that you need this amount of tank heating? I would think you would be ok in KY most winters. Do you have a working furnace? I would think that just keeping the trailer warm inside would do the trick till you get down below 20F for several hours. If you are stationary you can add some insulation between the tanks and the ground or put a skirt of some sort around the tank area. I expect adding some RV antifreeze to the sewer tanks would gain you a few more degrees of protection. You can run the fan on the furnace to circulate some air down there.

Perry

KYAirstream 11-13-2013 06:48 PM

I use my trailer year round and try to minimize propane use by using ceramic heaters, so am just curious about alternative methods of keeping the tanks warm for future years ahead. I happened to notice those reptile heat pads and other heat tape on Amazon and was just curious if anyone had success with alternatives to the RV heat pads. Those RV heat pads seem expensive for what they are, and considering how many are needed per tank, the cost really adds up.

Interesting idea with the waterbed heater. Anyone have experience with them?

KYAirstream 11-13-2013 06:58 PM

Quote:

Originally Posted by perryg114 (Post 1379610)
Where are you camping that you need this amount of tank heating? I would think you would be ok in KY most winters. Do you have a working furnace? I would think that just keeping the trailer warm inside would do the trick till you get down below 20F for several hours. If you are stationary you can add some insulation between the tanks and the ground or put a skirt of some sort around the tank area. I expect adding some RV antifreeze to the sewer tanks would gain you a few more degrees of protection. You can run the fan on the furnace to circulate some air down there. Perry

That's not a bad idea...simply layering fiberglass insulation between the tanks and the ground. A few unfaced faced bats would easily fill the void between the bottom of the tanks and the ground. Perhaps a tarp on the ground first to serve as a moisture barrier. Or better yet, the fiberglass bats enclosed in plastic. That would certainly be an inexpensive method and would be easy to do. Great idea!

KYAirstream 11-13-2013 07:08 PM

Quote:

Originally Posted by Skater (Post 1379421)
Interesting idea. In addition to what Protag said, the 'real' tank heaters are a much higher wattage - for example this one is 164.4 watts for 12"x20", while the reptile heater link you gave is 20 watts per foot - so about 30 watts for the same square footage. My guess is they wouldn't work well enough - the heat has to go through the plastic and warm the liquid inside, while being in a cold environment itself... It's one of those things - if it works, GREAT you've saved a bunch of money. If it falls short, well, that purpose-built tank heater probably would've been much cheaper than repairing/replacing the tanks might be.

The link you provided actually has pretty reasonable prices on these pads, even for the 120/12v pads. Other places I had looked were about the same price, but 3 pads would have been needed for an average size tank. Thanks for the link.

Skater 11-14-2013 08:22 AM

Quote:

Originally Posted by KYAirstream (Post 1379685)
That's not a bad idea...simply layering fiberglass insulation between the tanks and the ground. A few unfaced faced bats would easily fill the void between the bottom of the tanks and the ground. Perhaps a tarp on the ground first to serve as a moisture barrier. Or better yet, the fiberglass bats enclosed in plastic. That would certainly be an inexpensive method and would be easy to do. Great idea!

I haven't had our belly pan removed yet, but I thought there already was insulation in there. Probably not to the extent you're describing, though.

Quote:

Originally Posted by KYAirstream (Post 1379692)
The link you provided actually has pretty reasonable prices on these pads, even for the 120/12v pads. Other places I had looked were about the same price, but 3 pads would have been needed for an average size tank. Thanks for the link.

My idea is to install the tank pads, then re-route the furnace ductwork that's down there now back into the camper (with the possible exception of the one heating the dump valves). More heat in the camper should mean less furnace time, saving propane.

As someone else said, though, be sure you need them. Our B190 didn't have tank heaters for the gray/black tanks at all, and they were outside, underneath the camper, exposed (the fresh water tank was inside the camper). After multiple trips in freezing weather (with temperatures down to 17 degrees F), only once did we have any sort of problem - and that was that the dump valve froze. It takes a long time for a tank to freeze, and the temperature has to stay below freezing for it to happen, and any sort of movement of the water in the tank is going to slow that process down even further. We probably don't need the heaters for the tanks in our trailer given our usage pattern, but I'd like to have them just to be safe. (I'm making the assumption we'll be camping in cold weather with access to shore power - we just took a trip where that wasn't true, but it also wasn't cold enough to freeze tanks overnight.)

KYAirstream 11-14-2013 10:22 AM

Good points. Worst case scenario, as longer as the tanks aren't completely full, what's the worst that would happen? Frozen dump valve? I suppose the tank itself isn't likely to crack unless it is completely full....

Protagonist 11-14-2013 10:26 AM

Quote:

Originally Posted by KYAirstream (Post 1379938)
I suppose the tank itself isn't likely to crack unless it is completely full....

Half full is best for that. Assuming that the tank walls are straight up and down, then at half full they have the most flex if they do bulge from ice expansion, and are less likely to crack at a seam.

KYAirstream 11-14-2013 10:26 AM

A quick google search and it appears water typically expands 9%. That's not much, so I suppose unless a tank is full, the likelihood of real problems is minimal.

KYAirstream 11-14-2013 10:30 AM

With a 25 gallon tank, at half full at 12.5 gallons it might expand 1.125 gallons. That's not much--why would even 80% full be an issue when there would be plenty of room along the top of the tank for expansion?

Protagonist 11-14-2013 10:34 AM

Quote:

Originally Posted by KYAirstream (Post 1379943)
With a 25 gallon tank, at half full at 12.5 gallons it might expand 1.125 gallons. That's not much--why would even 80% full be an issue when there would be plenty of room along the top half of the tank for expansion?

Ice doesn't just expand up; it expands out to the sides, too.

wahoonc 11-14-2013 11:17 AM

Quote:

Originally Posted by KYAirstream (Post 1379941)
A quick google search and it appears water typically expands 9%. That's not much, so I suppose unless a tank is full, the likelihood of real problems is minimal.

You also have water in the pipes and fittings which will crack very easily under freezing conditions. I have had to replace more than my fair share of silcocks that have frozen in relatively mild conditions because they were either not drained or covered.

If your trailer still has the duct work from the original furnace still in it, I don't see why you couldn't add a small duct with a fan to carry heat from a near by ceramic heater into the tank area, bound to be cheaper than the tank pads, or having to replace a tank or fittings due to freezing.

Aaron :cool:


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