Aqua-Hot Service

Aqua-Hot hydronic heating uses tubing to run hot liquid into heat exchangers that disperse heated air into living areas. An Aqua-Hot heating system makes your RV more comfortable by offering a quiet system that produces even, moist, fume-free heat and continuous, on-demand hot water.

Master Tech RV stocks 98% of all of the Aqua-hot parts for your Hydronic Heating System.

Never be without Heat or Water!



Annual Service?

Is your Aqua-hot coming up for it's annual service? Click the button below to get your service scheduled!

I Want Service!

Click Below for Aqua-Hot Parts!



Our Exclusive Elite annual 32-point service has been proven to be the best way to keep your Aqua-Hot/ Hydro-Hot in top operating condition. We service your unit and do a thorough  inspection of all components which lowers risk of unexpected failure.
Scroll down for our pricing!

Aqua-Hot Benefits

  • Even Heating – no hot or cold spots
  • Instant Hot Water – hot water with zero recovery time
  • Quiet Heating – system is whisper quiet when running
  • Fume Free Heating – low emissions technology for odorless heat
  • Added Value – thousands of dollars of value added for resale

When Should I Turn Off My Aqua-Hot?

  • When refueling the vehicle.
  • Prior to cleaning or servicing the system, all power supplies must be disconnected.
  • When the system is winterized.


Winterizing the Aqua-Hot system will prevent damage to the domestic hot water loop. This copper tubing must be completely drained of water prior to storing the heater in freezing temperatures. To winterize the Aqua-Hot system, the domestic water storage tank must be fully drained and the demand water pump’s suction line must be disconnected. Using a piece of hose, one end of the hose is attached to the suction side of the demand water pump and the other end of the hose is placed into two gallons of RV antifreeze. Each interior and exterior faucet should be opened and closed, one at a time, until only antifreeze is present. The hose is then removed and the demand pump’s suction line is reconnected. All power supplies are then disconnected.

Monthly Maintenance

Monthly maintenance consists of visually checking the coolant levels in the expansion tank.

The 67/33 solution of water and antifreeze should stay at an appropriate level use a refractometer to determine your boiler antifreeze to water ratio. This inspection should only be performed when the Aqua-Hot system is heated. Adding solution to a cold tank will result in overflow as the Aqua-Hot heats up. Operating the diesel burner or electric RV heating element without the water and antifreeze solution will cause serious damage to the heater.

Service Personnel should clean and inspect all components for wear and tear.

Annual Maintenance

  • Annual maintenance should consist of a complete tune up of the diesel burner.
  • The fuel nozzle and filter should be replaced annually.
  • Connections to the fuel line need to be inspected and tightened, if necessary.
  • The combustion chamber can be gently scrubbed with a wire brush.
  • There is a flame sensor (photocell) which monitors the flame of the diesel burner.
  • During annual maintenance the photocell should be cleaned with a rag to remove any carbon deposits that may have built up.

Preventative Maintenance

  • For preventative maintenance the Aqua-Hot system should be operated monthly on the diesel burner for at least 10-15 minutes, unless the unit has been winterized. Keep in mind that running the system requires 12-Volts DC.
  • Different qualities of water can cause scaling problems and create less flow. Have the mixing valve inspected and cleaned once a year.
  • The copper tubing of the Aqua-Hot system is designed for fresh water and winterizing solution.
  • Periodic flushing with chlorine bleach, or other concentrated chlorine bearing chemicals, can cause failure to the domestic water loop if not completely rinsed and allowed to remain inside of the piping for extended periods of time.

Our Elite 15 Point Service Check List

Shop Side Access Elite Service


Yearly Per Service, not including parts
  • INSPECT NOZZEL, PHOTO DISK, ELECTRODES & PHOTO EYE *replace if neccessary, parts additional 
  • check voltage
  • clean unit
  • perform fuel pressure check 
  • inspect fuel lines & fittings
  • inspect wire harness
  • grommets & seals *replace if neccessary, parts additional 
  • clean combustion chamber tube & chamber
  • float switch inspection & test
  • inspect & test all water lines
  • inspect & test all pumps
  • inspect incoming connections 
  • Check antifreeze level *Add if needed 
  • Test fire for proper operation
  • any parts needed for service are not included in price above
Schedule Your Annual Service Today!

Special Rally Pricing

Center Access Elite Rally Service


Annual Service at Rally
  • Same Check list as above
  • Catch Us at a upcoming rally
  • This is Rally Pricing for Center Access Aqua-hot
Buy Now!

Side Access Elite Rally Service


Annual Service at rally
  • Same Check list as above
  • Catch Us at an upcoming rally
  • This is Rally Pricing for Side Access Aqua-hot
Buy Now!

What is Hydronic Heating?

  • Endless Hot Water, you'll never run out!
  • Quiet, interior Heating, no turning up volume on your TV!
  • Uniform Interior Heat Distribution, no hot and cold pockets.
  • Engine Preheating, for easier starting in cold weather (standard feature on the Aqua-Hot)

More Info on Hydronic Heating

Designed specifically for diesel-powered motorhomes, our RV heating systems are diesel-fired which frees you from the hassle of propane.

Our electric RV heating element provides heat in moderate, ambient temperatures. Because our RV heating systems use hot water to provide heat to the interior of your motorhome, independent heating zones achieve uniform interior comfort; you are able to put the heat where you need it only. Therefore, you can maintain the temperature in your bedroom at a comfortable 65º while maintaining your living room at 75º and your bathroom can be 80º.

Hydronic heat means heating with liquid. Operating similar to a thermos, the Aqua-Hot RV heating system holds water, heats it with liquid and keeps it hot for hours. This innovative heating method combines a water heater and furnace into one element, making it easier than ever to tackle the harsh weather conditions of winter camping, or merely take the chill off an early summer morning. The Aqua-Hot heating system is capable of handling all the coach’s heating needs out of one box, including bay heating.

The core of the Aqua-Hot heating system is a sixteen-gallon heat tank which contains a solution of 2 quarts water and 1 quart antifreeze. An internal coil wrapped around the tank heats the domestic water. This tank is thermostatically maintained at approximately 200ºF. The Aqua-Hot system is equipped with a mixer valve to prevent excessively hot water from flowing through the faucets.

Maintaining the temperature of the solution can be achieved by two separate heat sources — the diesel burner or the electric heating element.

When initially running the system, the diesel burner will heat in 10-20 minutes. On start-up, the electric heating element takes about two hours to heat.

Due to its efficiency, the diesel burner is the main heating source of the Aqua-Hot system. A thermostatic switch, set to cycle on and off according to an internal thermostat, controls the diesel burner. The amount of diesel used by the Aqua-Hot system is one to three gallons in a twenty-four hour period. However, a properly operating RV heating system will not continuously burn for that long.

A factory-set internal thermostat controls the electric heating element. Electrical power is about one-tenth the heating capability of the diesel burner and can be used in moderate temperatures when there is a low demand for domestic hot water. Both the diesel burner and the electric heating element can be used at the same time for automatic convenience.

In addition to the diesel burner and electric heating element, a third feature provides engine preheating as a supplemental RV heating source to reduce the operating hours of the diesel burner. While the vehicle is being driven, the engine’s heated coolant automatically passes through an engine preheat loop to transfer heat into the Aqua-Hot heat tank.

Once the heat tank is up to normal operating temperature, the heated solution of water and antifreeze passes through separate interior heating zones.

A series of plastic piping connected within the coach makes up a zone. Each zone is regulated by a thermistor located within the wall thermostats. The middle zone has a separate wall thermistor. It is by this method that the Aqua-Hot system puts controlled heat inside the coach. When a wall thermostat calls for heat, the chosen zone circulation pumps and the heat exchanger fans are activated. The heat exchanger fans operate on 12-Volts DC. Individual zones can be designated for heat to eliminate hot air from a furnace blasting throughout the entire coach. Heat introduced by the Aqua-Hot system will not dry out the air. Why? Because it does not “super heat” and remove any moisture content the air may have.

The Aqua-Hot system heats fresh domestic hot water automatically. Whenever a hot tap is activated, water is pulled from the coach’s domestic water storage tank and sent to the selected faucet. Since the internal coil surrounds the heat tank, the Aqua-Hot system is continuously heating domestic water on demand. The bay thermostat is set between 45 and 50 degrees Fahrenheit to prevent freezing of the domestic water system located within the coach’s bay area.


Aqua-Hot Engine Preheat Feature

Engine coolant can be preheated in cold weather by activating the Engine Preheat switch located on the dash panel. This will propel the Engine Preheat circulation pump to move the engine’s coolant through the Aqua-Hot’s engine preheat loop and warm the engine for easy starting. In colder temperatures the engine preheat feature should run for a couple of hours or more. This pump can be left on overnight if it would be beneficial to do so. The Aqua-Hot system will not overheat the engine. However, the Engine Preheat switch should be off when engine preheating is not necessary. When driving the coach, the preheat circulating pump must be off.

Prepare System For Use

To flush out the antifreeze and prepare the system for use, the fresh water tank is filled, the demand water pump is turned on and all faucets, interior and exterior, are turned on, one at a time, until clear water is present.


If the diesel burner fails to operate, try the following troubleshooting tips: First, check to insure that the burner’s indicator light is glowing. If not, turn the burner control switch off and then on again to reactivate. If the light still fails to come on, the diesel burner has malfunctioned, or the bulb is burned out.

Listen for the motor (located under the Aqua-Hot service cover) to determine if it is running. Determine if any air is exiting the Aqua-Hot exhaust pipe by placing a hand roughly six inches from the pipe. If the motor can’t be heard running, or hot air is felt from the exhaust pipe, inspect for blown fuses, loose wire connections or loose plug connectors. Now that you know the Aqua-Hot system, you can use it to obtain virtually unlimited hot water, controlled RV heating and preheating during any season of the year.