Are Electric Holding Tank Heaters standard equipment?

Most RV Manufacturer's in North America still offer UltraHeat systems as either standard equipment or a stand-alone option. Some offer them as a part of a Four-Season package upgrade option. Many European Manufacturers of leisure vehicles also offer UltraHeat, or similarly branded as "TankBlanket™" in some Euro Markets. Before you purchase your New RV or Leisure Vehicle, ask your dealer if the holding tanks have either of these anti-icing brands as O.E.M. standard equipment or in an upgrade option. Just having "Heating Pads" installed doesn't mean they are UltraHeat products. Because we're so popular, we have been flattered with overseas knockoffs that some RV Manufacturers are willing to use. These knockoffs have even gone as far as copying and using our same part numbers and label wording that we have always used, making them look just like ours in most every way. They cost less, and are less effective because they produce a much smaller amount of heat or BTUs. They spout un-tested claims of anti-freeze protection in greater sub-zero temperatures than UltraHeat products to get the sale. In most all case scenarios it will take two or even three of these other heat panels to perform with the same results of just one of our UltraHeat RV heat panels. We have been put to the test in RV’s since the 1980’s and have seen all types of Winters, if you have experienced cold weather RVing with our products installed, you know they work ! Manufacturers using these knockoffs are still able to advertise and charge the same amount of dollars for these “Heated Tanks" options and four season packages, compared to ones using our UltraHeat original version. In most cases, they are covered up within enclosed underbellies, were you can't easily inspect and identify them. They think you'll never know the difference, until you need them and it's too late, your frozen up and you own it! The big question is this, if they are willing to cut corners on something in a up-sell feature they are charging you for, where else are they cutting corners? And "NO" the cost of damage repair due to freezing isn't covered under their Warrantee! Every winter we have a great many phone conversations with RVer’s asking about upgrading to UltraHeat system products because what they have installed hasn’t worked like the Manufacture’s Dealer or advertisements said it would. Far too many are frozen up solid, stranded somewhere due to the damage that has consequently occurred and finding they have to cover the unexpected cost and repairs that can run into the thousand dollars. Even RVs that have OEM installed UltraHeat Holding Tank Heaters may still require additional heat panels in order to completely protect their system during cold weather use. To reduce costs in a competitive market, almost all RV OEMs overlook protecting the below floor fresh water supply lines and drain pipes that are located between the holding tanks and gate valves even though these areas will generally freeze first and render your systems unusable. By offering “Heated Tanks” using UltraHeat products, the OEM is supplying the end user with the best “basic” system on the market, which can be further improved upon depending on individual needs and usage. For this reason, we always recommend to familiarize yourself with your unit’s design and consider how you plan on using your RV. Where needed, add additional heat pads and other modifications to insure the desired performance in the cold weather conditions you plan on using your RV. It still is a “Buyer Beware” market; insist on UltraHeat by name and in writing! Educate yourself, ask a lot of questions, and understand what you’re getting and will it fit your needs before you purchase. UltraHeat products are proudly “Made in the U.S.A.”, by an American Company, supporting the American Worker and Supply Chains!

Can I use this RV year round (summer, spring, fall & winter)?

Consider where you live, travel, and in what climates you plan on using your RV prior to buying a new or used Model. Look at the fresh water line routings, are they running straight up into the cabin or across and below the floor? Anything below floor will freeze if not protected when using an RV in cold weather, and long fresh water basement runs may get to be cost prohibitive and hard to guard against freezing. Consider double pane windows, and look at the "R" rating of the side walls, floor and ceiling. Just like your home, a poorly insulated unit will take more to heat or cool, and will be less comfortable when used in weather extremes. Ask if the refrigerator has a winter package installed to keep it working in colder weather. Did the Manufacture consider and design this Unit for possible four seasons of use; does this unit come equipped with a cold/hot weather up-grade option? You’ll need UltraHeat electrically heated holding tank and pipe heaters installed on your drainage system to ensure use of your plumbing in cold weather. For extended use in cold weather seasons, other upgrades may have to be added based on Model and Manufacture of the unit. Educate yourself on what's available, look at the RVing blogs; visit other sites like this one. Very few models are designed with cold weather in mind, and some that are do it better than others. An informed buyer is a smart one! Getting an RV that meets your needs or one that can easily be retro-fitted to do so, will be far less expensive and more gratifying in the long run.

The RV I'm looking at has an enclosed underbelly with air from the furnace blowing into the area around the holding tanks in place of Electric Heat Panels. Do I still need to use UltraHeat RV Holding Tank and Pipe Heaters?

This is commonly called “Ducted Heat”, only effective when the furnace is continuously running, and only effective down to temperatures around the mid 20's°F (-6°C). RV's that try to use forced air to heat the underbelly will typically use a 2" or 4" flexible duct directly under the furnace to heat the entire underbelly. This would be like trying to heat the bedroom of your RV with the door shut and the only heat vent located in the living room. Air movement within a force air heating system will take the path of least resistance. Blowing air into an un-vented chamber is like blowing up a balloon, once back pressure is achieved, air will no-longer be easily driven into it. The temperature control for the furnace is located in the cabin, not below the floor in the basement, once the better insulated and protected cabin space is warmed up to the desired heat the furnace shuts off. Who knows what the temperature is around the holding tanks, was it enough to stop a freeze-up, and how long will the heat last down there with the furnace off? What if you are using Electric Space Heaters in cabin, not Propane to conserve fuel and the cost of it like many do? Many times electric is included with rent, or at the minimum is less expensive to use. How do you heat the Holding Tanks and Drainage then? Something else for you to consider; forcing moist heat from the propane furnace into a cold, dark and poorly vented area of the enclosed basement will produce condensation (look at your cabin windows As an example). This is the perfect environment to eventually develop the mold organism, and create an odor and allergy possibilities. Does this common problem sound like a healthy influence to you? “Heated tanks using Ducted Heat” is a Sales Decoy; someone coined the term many years ago in order to eliminate the cost to actually protect the systems, believing that most RVer’s would never use their units in colder climates. And if they did, the sale was already made and too late for the Consumer, hence the phrase “Buyer Beware” These are just a few of the many reasons why UltraHeat RV Heat Panels are still necessary! Giving your RV's system of holding tanks, pipes and gate valves the proven performance and protecting from freezing down to -11°F (-24°C) just by themselves and even lower with additional modifications. UltraHeat, the right heat, right where it's needed!

What needs to be protected from freezing in the RV when it is used in cold weather?

• Fresh Water Tank (potable drinking water) plus exposed water lines below floor.

• Gray Water Tank(s) (kitchen and/or Bathroom sink, Galley, shower water) plus straight pipes and elbows between tank and termination valve (gate valve).

• Black or Sewage Tank (bathroom waste) plus straight pipes and elbows between tank and termination valve (gate valve).

• Discharge Gate Valves.

One of my panels is peeling back a little, can I get some glue to reattach, or what should I use?

The adhesives use in our products are of a proprietary formula, designed not to breakdown and even increase its adhesion properties in the ageing process. The method in which our adhesive is applied gives it a stronger molecular concentration, giving it a far superior adhesion capabilities than others used by most other look-a-like products, which frequently just dry out and release. The most common scenario in which our adhesive will start to release and have a panel peel away is when the mounting surface is not cleaned or impropriety prepared prior to installation of the heat panel. In the event a panel may start to come loose, we have tested a wide array of aftermarket adhesives, and have compiled a list of ones that can be commonly found almost anywhere that will work to reattach our UltraHeat products. Click Here to review this list.

Can these panels be installed on a metal tank?

The standard UltraHeat heat panels are designed for use on an RV meeting the Codes and Standards of that Industry, code dictates a tank constructed of Poly, which is why these particular heaters can only be installed on Poly tanks. The good news is that we offer a variety and variations of heat panels to an array of other Industries that would include installation directly to metal. Recently we have also added the opportunely to custom order this upgrade online at any time on certain standard models for the RV Industry. (Click here) to review these models.

Why can't I just use RV Antifreeze to keep my tanks from freezing?

<h5 class="font_5">Originally Posted by Camco in their FAQ, from this PDF page:</h5> <h5 class="font_5"> </h5>

"Q. How much water should I add to your -50 RV Antifreeze to achieve a -25 burst protection?"

"A. Camco -50 RV Antifreeze should not be diluted. It is a pre-diluted solution that is designed to be used full strength. Additional water dramatically alters the expansion properties of the solution, making an adequate burst protection difficult to achieve."

How many UltraHeat Tank Heaters will be needed to protect my recreational vehicle (RV)?

One (1) UltraHeat tank heater (sized properly) per holding tank (up to a 75 gal (284 L) maximum). On larger volume holding tanks, multiple heating panels can be used in combination, wired in parallel or independently controlled. The average RV produced in North American has three holding tanks however there could be as many as five tanks and each tank that is located below the floor would require a heat panel. Each Tank Heater Panel is rated for the maximum RV holding tank capacity it will protect against freezing down to our testing and design bench mark of -11°F (-23.9°C) with only the heat panel itself. Much lower temperatures like -40°F (-40°C) can be sustained with additional installation modifications and insulation.  When reviewing your overall system, also consider heating the drainage piping between the waste holding tanks and termination valve (gate valve), these locations are the are the first to fill and freeze due to being the low points within the system. Also consider the fresh water supply lines between the tank and unit floor.

Can I connect these heat panels directly to the battery bank of my RV?

We wouldn’t recommend doing so, and this is why. Pulling power directly from the battery bank will of course in time drain down the batteries, and could drain power so low to a point of permanent damage to the battery. Running the 12 Volt heat panels power through an onboard converter is much safer for your onboard electrical system. When operating off of the batteries alone, the converters today have a built-in safety function that prevents draining down the batteries to the point of damage, shutting down the 12 Volt systems prior to this point. When running off shore power or a generator, power is stepped down to the 12 volt system from 120VAC and divided up and supplied to the systems using 12 VDC, the converter just sends a smaller trickle charge to the battery bank to either maintain or recharge. This trickle charge is not enough to keep up with the amp draw of a series of heat panels, or any other items that would be drawing directly from the battery bank and would in the long run drain down the batteries, even though you have a 120 Volt supply and are charging the batteries. Like filling a swimming pool with a garden hose, and pumping the water out with a fire hose at the same time, not enough to keep up with it.

What is the lowest temperature the UltraHeat heat panels are good to?

While each RV or Leisure Vehicle is different, our overall product design benchmark and testing is -11°F (-23.9°C). This is on an RV holding tank (with the properly sized heat panel), mounted below the floor and totally exposed to the elements. Lower temperatures can be achieved by additional modifications to the RV, once the UltraHeat system is installed and tested; these are some of the suggested ways to improve the performance:

• Enclosing the underbelly or just the area around the Plumbing Systems.
• Adding any type of insulation around and covering the plumbing system. (This is not mandatory, as a cautionary measure and to meet the Federal Vehicle Safety Standards, if you do use insulation we recommend using a type designed for high heat applications and/or carries a Class A or Class 1 fire rating).
• On extended stays, skirting the unit.
• It’s OK to oversize the holding tank heater; install one rated for a maximum of 75 gal. (227L), on a 40 or 55 gal. (151.4 - 208L) capacity tanks, this allows more heat to be applied.

When should the UltraHeat RV Holding Tank Heaters be turned "ON"?

Only when fluids are present within the holding tanks and drainage pipes, and the outside temperature approaches freezing and remains below. If either of these criteria is not present, heat panels associated within either the entire system or independent sections must be powered or switched ‘OFF” Failure to observe either, could result in damage to your system.

When do you turn "off" the Heat Panels or the entire system?

• OFF - when there is NO liquid in the tanks or pipes

• OFF - when the outside temperature remains above freezing.

• OFF - when the black and gray holding tanks and drain pipes are being dumped.

• OFF - when the fresh water holding tanks and supply pipes are being drained for storage or empty.
• OFF - when the RV is connected to city sewer and the gate valves are open (free draining is never recommended, especially in cold weather RVing) .

Is there any maintenance on these heaters?

Inspect your unit periodically for damage, loose wires, etc.. UltraHeat heat panels are designed to function and have a proven track record of 12 plus years of operation and use. Realistically, we’ve witnessed our heat panels that were installed decades ago, still hanging onto the bottom of an RV and functioning thus far today! We build in quality, not obsolescence! With this in mind, we now have extended our limited warranty for RV related heat panels to Lifetime.

I have something else I’d like to apply heat to, I think that one of your panels may do the job; can I use your panels for something else besides an RV?

The UltraHeat brand of RV Heat Panels we talk about on this site are designed just for use in Recreational or Leisure Vehicles, intended for a particular usage and to meet the codes and standards of this Industry. However, these are not the only types of heat panels we produce, or the only Industry we service. If you have a unique application, a question or just want to talk about what you are trying to do, send us an e-mail or give us a call. As the Manufacture, we know that we’ll have a possible solution for you. (Contact Us)

How can I test our Tank Heater to see if it’s working?

This is the most common and easiest way to test the operation of a UltraHeat RV tank heater, you must have direct access to the heat panel itself due to a built-in sensor that controls the panel based on the fluid temperature of the contents within the tank itself. Once power is applied, this sensor basically switches ‘on’ the heat panel when tank fluid temperatures drop below approximately 44°F (6.6°C), and ‘off’ once tank fluid temperatures rise above approximately 64°F (17.8°C). In order to test the operation, you have to fool the sensor into thinking the fluid temperature is below the 44°F (6.6°C) threshold, thus completing the circuit and allowing electricity to flow through the panel to heat. To perform this test, first find where the power leads enter the back of the panel, near to this point you will find a small hard lump about ¾” (1.9cm) long and ¼” (0.6cm) wide, this is the sensor. Place a Ziploc baggie full of crushed ice over this area and temporary secure it in place with something like duct tape, supply power to the panel and wait for the ice to fool the sensor, this may take some time to complete (20 – 30 min is not uncommon in warmer weather). Once the sensor has reset, the panel will start to warm, and you will be able to feel this change through the panel’s backing. Once this is confirmed, turn ‘off’ the power and remove the bag of ice, etc. For normal operation of your tank heating system, please follow the instructions found under "The Basics" on this page. Please note; there should be some fluids within the tank prior to preforming this function as a safety measure to prevent damage in the event that the heat panel is allowed to remain powered ‘on’ for a longer period of time than needed for this test.

How do the Gate Valve Heaters work, and when should they be turned on?

When we talk about gate valve heaters, we ask you to think about the “Spare Tire for your car or truck”. You don’t use it all the time, however when you need it, you’re glad you have it! Gate Valve Heaters are thought of in much the same way, rarely ever used except when the valve is frozen closed and you’re trying to vacate your systems. These are what we call “Hot” heat panels, designed to rapidly penetrate the thicker plastic with enough heat to thaw the frozen tracks for the gate valve. Intended to work primarily with “Valterra” gate values (the most commonly used within the Industry), or similar models with a smooth and level flat surfaces on the exterior three sides of the gate body itself. The gate valve heaters should be controlled independently from all the other heaters, with a separate on/off switch just for the gate valves. We recommend installing the switch inside a compartment close to the dump valves, covenant and away from the other Heat Panels manual control switching. If needed, turn the Gate Valve heater "ON" for approximately 5 to 7 minutes, or until the valve is freed. Turn “off” the switch and evacuate the tanks as you normally would. These heat panels are designed for short term use, and only in freezing cold weather where the gate valve has been frozen closed.

How does the Model 3600 (dual voltage) Tank Heater work?

The Model 3600 Tank Heater is actually two separate tank heaters in one, a 12 Volt (13.5 VDC) heating element and an isolated 120 Volt (AC) heating element. Each heating element operates independent of the other. Both are rated for holding tank volumes of 40 gal maximum (151 L).

After I've installed the UltraHeat panel, can I put some insulation over it, and in direct contact with the panel?

Yes, insulation will only improve the performance of our heat panels. It’s like dressing yourself in cold weather, the warmer you dress, the less body heat you lose. Reducing how fast the tanks and drain pipes loose heat, decreases the need for the sensor in the tank heaters to activate themselves "on", and conserves energy consumption. It also will aid you in achieving use of your Unit in much lower temperatures. Our panels are design to direct heat towards the mounting surface; the backing only gets a little warm. (This is not mandatory, as a cautionary measure and to meet the Federal Vehicle Safety Standards, if you do use insulation we recommend using a type designed for high heat applications and/or carries a Class A or Class 1 fire rating).

My holding tank is sitting on a plate or platform, can I sandwich the heat panel between the tank and the plywood platform?

Yes, pressure applied to the heat panel itself will not damage the panel. There are some precautions that do have to be made: The built-in sensor may be affected by the pressure, we do require that were the sensor is located against the platform, a valley is carved or a hold drilled out in the platform to relieve the pressure against the sensor when the tank is full. The sensor is easy to find on the tank heater panel, were the power leads entering the heat panel you’ll feel a hard lump approx. 0.25” X 0.75” (6.35mm X 19.05mm), that’s the sensor. We also recommend that between the heat panel and the platform, you place something like a sheet of Styrofoam, something to cushion against friction, vibration and rubbing when the RV is bouncing down the road

My holding tank has a metal strap holding it up, right where I would place the tank heater, can is install the holding tank heater over the metal strap?

Our heat panels designed for RV, Caravan or Leisure Vehicle use are not designed for direct installation to an electrically conductive surface, so the answer is NO, this would most likely short out the heating element and cause the heat panel not to work. We recommend that you temporary drop the strap away from the tank (please ensure that the tank is empty prior to doing this), install the heat panel, and re-install the metal strap over the top of the heat panel. A couple of things to keep in mind, when deciding where to place the heat panel, make sure that the sensor (hard lump approx. 0.25” X 0.75” (6.35mm X 19.05mm) were the power leads enter the heat panel) is not going to be under the metal strap when you’ve completed the project. We also recommend that you place something like a thick rubber strip between the metal strap and the heat panel, something to reduce the friction and possible cutting into the heat panel by the metal strip from vibration when traveling down the road.

Do UltraHeat Pipe and Pipe Elbow Heaters work with sensors?

Pipe and Pipe Elbow Heaters do not have a built-in sensor to control when they activate and deactivate once powered “on” like the tank heater models. They are either “on” or “off” all the time. Pipes have smaller volumes of fluid, and changes in temperature will occur much faster and many more times within a shorter period than in a large volume holding tank. They would be turning "on/off" all the time, with no advantage in the energy savings we see in our RV Tank Models. As the temperature drops, testing has proven that it's best to just throw continuous heat at the pipes. If you are concerned about energy conservation, while it will not eliminate the need for a manual “on/off” switch, consider our “Ambient Temperature Master Power Control Kit”. It will only activate the entire system when outside temperatures drop to 35°F (1.7°C) and deactivate the system once it recognizes a rise to 45°F (7.2°C). (For info – Click here)

Are 120 Volt (AC) UltraHeat Pipe and Pipe Elbow Heaters available?

All UltraHeat Pipe and Pipe Elbow Heaters are only powered with 13.5 VDC (12 Volt). Frankly we haven't found much of a sales market for 120 or 240 VAC pipe and Pipe elbow heat panels in the RV Industry. And there is also the safety aspect, drain pipes often hang very low and are more accessible to small children and animals, ‘Higher Voltage’ heating panels could be dangerous when installed in these areas.

What does the Ambient Temperature Master Power Control Kit do, and do we need it?

This kit was developed by us to basically take the guess work out of when to power "on" and "off" the UltraHeat heat panels. It uses an electronic sensor to monitor the air temperature either outside the RV or can be mounted within an enclosed underbelly. Once the air temperature drops to 35°F (1.7°C), the sensor will activate a power contact relay(s), and complete the circuit and supply power from the source to the total UltraHeat system. Power will remain “on” to the system until this sensor monitors a rise in ambient air temperature to 45°F (7.2°C), at which time it de-activates power to the relay(s) and the UltraHeat system is turned “off”. Please note that is Kit does not eliminate the need to independently switch each plumbing system (i.e. gray, black or fresh). If one or more are void of fluids they each must still have the ability to be manually switched “off” or separated from this system, and “on” or added back to the system as the utilities have been used. This master control kit gives you the peace-of-mind that the entire system will be automatically powered “on/off” when it needs to be, based on outside temperature, keeping the UltraHeat system working just outside the freezing zone. Great if on occasion you are away from your unit for extended lengths of time, looking for added control over energy consumption or just don’t want to be bothered continuously monitoring the outside temperature and manually powering “on/off” the system. This Kit is a recommended option to any new UltraHeat system, and can be easily added to an existing one.

Is the Ambient Temperature Master Power Control Kit only for 12 VDC systems, or can it be used with the 120 VAC models?

The way we’ve designed this control kit it can work with either voltage or both at the same time. The electronic sensor itself only operates on 12 VDC, however it controls one or more power relays, the built-in contact switches of the relays are each rated for 30 Amps at 120/277 VAC or 20 Amps at 12 VDC. Each relay has two independent set of contacts, one can be used for 12 VDC and the other for 120 VAC, both for 12 VDC or both for 120 VAC. You can add another relay (or more if needed) by wiring the relay coils in parallel and add more sets of switched contacts to wire in any combination. This kit only controls the main power feeds to the overall UltraHeat system from the power source, powering it “on/off” based on the ambient temperature. In does not replace the need to independently switch each plumbing system (i.e. fresh, gray and black), and also separating each voltage type 12 VDC and 120 VAC, with a “on/off” you can manually switch to remove any section out of the controlled system by switching them “off”. Example: You are using the Model 3600, dual voltage and dual element holding tank heaters. One side of the heat panel is 12 VDC and the other is 120 VAC, your RV is parked and attached to 120 VAC shore power and there is some fluids in all your holding tanks, you only want to use the 120 VAC sides of the tank panels. Manually switch “off” the 12 VDC switches independently controlling each tank, and switch “on” each 120 VAC switch associated with the same. When the temperature drops and the sensor activates the relays, only the heat panels that are manually switched to “on” will allow power continue through and flow to them. You’re hitting the road again and disconnecting from 120 VAC shore power, manually switch “off” each 120 VAC plumbing system and switch “on” the 12 VDC as needed (only if fluids are present). Example: You are hitting the road, all waste holding tank systems are empty, but your fresh water tank is full. Manually switch “off” all waste storage systems and keep the potable fresh water “on”. With this master control kit integrated into the wiring system, once the Ambient Air Temperature around the electronic sensor drops to 35°F (1.7°C), it will power up the entire system and activate only those independent systems (gray, black, fresh) that have their manual power switches in the “on” position. Once Ambient Air rises to 45°F (7.2°C), the master control will power down ( turn off) the entire system.

Why do the 12 Volt Heaters draw so many amps?

We work within two scientific areas of rules that can't change, Ohm’s Law (basic laws of Electricity) and General Physics. In Physical Science it takes ‘X’ amount of heat to heat ‘X’ amount of water to a temperature so it won’t freeze. In order to produce this amount of heat needed to realize this down to our sustainable intercompany benchmark of -11°F (-23.9°C) and lower, it takes ‘X’ amount of energy or in our case, electricity and amperes . Ohm’s law teaches that when producing this amount of electrical energy or power, as you reduce the amount of force used (i.e. voltage); you have to increase the amount of flow or amps to retain the same amount of energy output. Basically, to accomplish the same heat output; the lower the voltage the higher the amps, and vice versa. This is why we consider how we use voltage and consume amps, and one reason why our Tank Heaters (our largest Amp draw items) are sensor controlled. Once powered “on”, the built-in sensor will power cycle the tank heat panel “on/off” based on the temperature of the tank’s fluid contents. The sensor will cycle “on” once the fluids drop to approx. 44°F (6.7°C), heating up the contents up to approx. 64°F (17.8°C), then cycling “off” and allowing the volume of fluids to slowly loose temperature back down to approx. 44°F (6.7°C), limiting the amount of time they are drawing power. There are many variables that will determine how long this temperature drop will take; amount of fluids present, ambient temperature, and most important is the rate of heat loss. If you are looking to conserve energy, there are a couple of common sense ways we would recommend.

• First, reduce the rate of heat lost by enclosing and insulating your plumbing systems after installing and testing the UltraHeat system.
• Wait to vacate your waste holding tanks until they are almost full, larger volumes of fluid take longer to change in temperature than lower volumes do.
• Then you’re sure the ambient temperature will remain above freezing, power “off” the system as soon as you can. (We suggest you look at our ambient master power control kit to automate this function)
• With extended stays in one location, consider skirting your unit in some way, this will reduce the wind blowing under your unit. This will reduce heat lost to both your plumbing and the Cabin floor, also greatly diminish temperature cycling within your units living interior space. Talk to a local awing or boat cover producer about making something custom for your unit that can easily snap or turnbuckle on and in place when stationary. You and others will like the look; the cost offset is either in energy savings or added value when it comes time to re-sell the unit. You may find yourself using it more than just in cold weather, as many we’ve talked to have.

I want to retrofit my RV with your products, but my 12 volt power converter doesn’t have enough unused fuses.

You would have a couple of options,

• You could use the M3600 tank heaters, discussed in more detail within this FAQ page.

Will the UltraHeat Heaters damage the holding tank if no liquid is in the tank when the Tank Heater is "ON"?

If the holding tank or heated drainage pipes are completely empty and the heat panels are powered ‘on’, there is a possibility that damage could occur, especially if the ambient temperature is above freezing. When there is liquid in the tank and piping it absorbs and distributes heat away from the heater and mounting surface, drawing the heat into itself, acting like a Heat-sink (much like placing a pot of water onto the stove). There needs to be just enough fluid within the tank or piping to cover the bottom or the heating element, in most cases a gallon or two. Without liquid present, it would be like putting an empty pot on your stove top and turning on the burner, the pot will get hot and scorch or possibly burn if left unattended. To ensure proper operation, Always follow the instructions found in “The Basics” section of this page on when to turn ‘on’ and ‘off’ your UltraHeat system.