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What Is Aqua-Hot or Hydro-Hot in an RV?

What Is Aqua-Hot or Hydro-Hot in an RV?

The addition of an Aqua-Hot or hydronic heating system to your RV is a valuable one. While they are usually factory additions, they could add around $7,000 to the value of your vehicle. Working with this system is excellent once you understand how it functions. If you are considering whether to invest in this upgrade for your RV, you’re in the right place.

Let’s dive into the Aqua-Hot or Hydro-Hot system now. 

What Is Aqua-Hot? 

What is an Aqua-Hot system? It may be complex, but it’s fascinating how the whole process works. The system provides heat and hot water inside your RV, no matter where you are parked. 

These are boiler-based systems that use a special antifreeze solution to circulate heat into the coach.

In addition to heating the air in the coach, the system also heats the water. With this setup, you could wash the dishes and take a hot shower without waiting for the water to heat up again. Aqua-Hot is the icing on the cake when you’re into “glamping.” 

aquahot control panel
Hydronic heating systems have multiple heating options

The Aqua-Hot system will also preheat your diesel engine when you’re traveling in cold climates. It can run off the heat from the engine, an AC plugin, your generator, or the RV’s diesel burner. The power versatility means you’ll never have to go without a warm cabin and a hot shower.  

How Does a Hydronic RV Heating System Work? 

The Aqua-Hot hydronic RV heating system transfers heat from various energy sources into a liquid antifreeze solution. Frequently the heat sources are electric elements or a diesel boiler but sometimes it can be propane as well. The hot liquid flows through system loops within the RV that flow past a series of vents inside. 

hydronic RV heating System Vent
Air heat exchangers are usually located near the floor of the RV and will have a small fan that blows air through them. They are selectable and usually very quiet compared to forced air furnaces.

Small fans pass air through those vents that is warmed by the hot liquid, giving the interior of the RV a pleasant and even temperature throughout each room. Usually, there are many zones that are controllable so its easy to control the heat.

exposed air heat exchanger for aquahot
This is what the backside of a heat exchanger looks like with the fan mounted in it. This exposed unit is for heating the basement and water lines and tank.

However, that’s just one part of the Aqua-Hot system. In addition to heating air it also heats the water in the coach. Before the hot liquid passes into the interior heat exchangers it goes through a water exchanger to transfer the heat into the water supply. This in turn can provide unlimited on-demand hot water as long as the boiler is running.

The hydronic system can also pump heated fluid into your diesel engine to preheat it before hitting the road. This feature is especially helpful when you wake up to freezing temperatures but need to get on the road in a hurry.

The Many hydronic heating functions
Hydronic RV heat is very versatile and performs many heating functions

In addition to all this, the system also can use the preheat circuit to get the heat off the engine while driving. The system works in reverse taking engine heat and heating the boiler fluid. This way the coach can be heated through the air exchangers while driving.

The versatility of the system is impressive.  

Pro Tip: We found 7 of the Best RV Water Heaters that we think your RV water system would benefit from!

How Do You Fill Aqua-Hot?

Since the aquahot is a hydronic system it has its own working fluid that is sometimes called coolant, antifreeze or boiler fluid.

Fill up your fresh water tank and let your Aqua-Hot system do the rest of the work!

The system will have an overflow tank somewhere nearby that needs to be kept at the recommended fill line. You dont want this too full as its also used for system fluid expansion.

If you’re looking to refill or flush the coolant in the system, that’s a much more technical question. It is also a question you should know the answer to before purchasing an Aqua-Hot heating system. 

You should flush and replenish the coolant in your system every two years to keep it well maintained. 

You’ll have to drain the coolant, mix some fresh fluids, pump the new coolant into the system, and flush the excess air from the lines to complete the refreshment. If you need a thorough walkthrough, you can find plenty of “how-to” videos on the subject online. 

Aqua-Hot Maintenance - RV Antifreeze Flush Full Video

How Long Does It Take for Aqua-Hot to Heat Water?

If the system is already hot, you will get hot water to your taps in a matter of seconds. If the primary burner is on it should last as long as the tap is on.

A full heat up with your Aqua-Hot heating system including air vents could take around an hour, depending on the circumstances and size of the system. The system will heat up faster when switching on the electric and diesel power sources.

Person showering in an outside RV
Whether you shower indoors or outdoors, warm water is a must!

How Do You Winterize an Aqua-Hot System? 

Winterization of the hydronic heating lines is not necessary because they utilize a an antifreeze solution that will not freeze. This is why its critical to use the correct fluid in the system.

The water heating size of the system will need to be winterized, however. This can be accomplished by blowing out the lines or flushing them with antifreeze. If you expect freezing temperatures be sure to do this or you will have serious damage to the system.

Pro Tip: Prep your RV for the cold with these tips on How to Heat Your RV Tanks and Prevent Freezing.

boiler antifreeze
The working fluid within the system is an antifreeze that does not need to be winterized, winterize your water system however just like any other RV.

How Much Is an Aqua-Hot?

We recommend that you purchase an RV already fitted with an Aqua-Hot system. Retrofitting the hydronic heating system will cost a pretty penny. A retro-fitted system could be pricey to install. 

The unit itself may only cost around $6,000, but the work you’ll need to do to install a whole hydronic heating system in your RV is extensive. You’ll get a bit of equity in your RV with the installation, but be prepared to make a few payments. 

Aqua Hot System | RV How To: La Mesa RV

Is Aqua-Hot in an RV Worth It?

In short, definitely! You get unlimited on-demand hot water, quieter efficient interior heating, engine heating, and heat of the engine all in one system. The ease of use and comfort with an Aqua-Hot system is worth the investment. You’ll have a pearl of an RV with this fancy heat source, and there’s nothing amiss about adding value to your bus.

What size system does your RV need to suit your travel party?  Drop a comment and let us know!

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Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of “Go North” on Amazon Prime Video, co-founders and instructors of RV Masterclass, and contributing authors for and an Arizona travel guide.

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Wednesday 17th of May 2023

I have the Aqua Hot in my 2006 Beaver coach and the invention of the system is amazing, I can see why parts are still available with OEM

Mortons on the Move

Saturday 24th of June 2023

We love ours for sure!


Saturday 26th of February 2022

Having an on demand system is a wonderful luxury. Having really hot engine-heated water when you are stopping for lunch when travelling is especially convenient.

I look forward to a follow-up post "aqua hot vs oasis: which is the better unit?" .