Aqua-Hot Antifreeze Flush Complete Walkthrough

Aqua-Hot RV boiler systems offer some serious advantages to that of their less expensive and more common RV hot-water heater counterparts. Aqua-Hot systems offer unlimited hot water, often run off of your RVs primary fuel tank (diesel models) and also heat an RV much more evenly than propane furnaces. They offer multi-zone support, do not as severely affect internal humidity levels in your RV and can even be used as engine block heaters to start your engine in colder weather. We have had our challenges with our Aqua-Hot system yet for the most part we are very happy with the purchase and are glad we sprung for an RV that had this feature. Stay tuned and make sure to subscribe for more information on that topic coming shortly but in the meantime lets do some routine maintenance!

Aqua-Hot Antifreeze Explained

With all that functionality, the systems do require additional maintenance to keep them running optimally. Today we are going to review the process of changing our Aqua-Hot system antifreeze. There are two types of anti-freeze fluid recommended by Aqua-Hot. Both are Propylene Glycol antifreeze but they are made by different manufacturers. Most dealerships use Century brand antifreeze which is green in color however most retail establishments and online RV retailers stock Camco which is pink in color.

You can mix the fluids (all though you will find a lot of posts on forums saying you shouldn’t) however if you choose to mix you will end up with a brownish color fluid. This brown mix fluid will work fine but may make things more difficult to troubleshoot should you have problems down the road. This is because brown fluid looks similar to contaminated fluid that may have been exposed to water contaminants and other undesirables. It will be harder to identify other system issues since fluid color is one of the indicators of something wrong with your system.

We recommend going with the pink Camco fluid as its more readily available and also available in a high-concentration 32oz bottle which is much easier to carry in your RV for quick top off jobs. That said, if you find your system to be low, it is always better to add fluid then to let the system antifreeze level be low so use your best judgement. You can learn more about the fluids below in the FAQ section link which will bring you to a handy page kept current by the manufacturer.

Antifreeze Flush Intervals

This topic has a lot of discussion around it but in short the frequency in which you should change your fluid is largely dependent on how much you use your system. Under normal conditions we find that we like to change out our fluids every 24 months to ensure trouble-free operation. Many users report issues with check-valves which are located inside of the Aqua-Hot system and can stick or freeze due to lack of use or poor fluid quality. The propylene glycol fluid has a high viscosity (slippery) to minimize these issues and as a result we recommend changing the fluid regularly as fluid viscosity can breakdown over time.

Flushing Instructions

The video above will do a lot to explain the process but i’ll summarize the steps in this section for easy reference.

1. Park on flat, level ground (this is actually important)
2. Set your thermostat in your RV to “OFF” to ensure the system isn’t calling for heat while you are working.
3. Turn off the Aqua-Hot system (boiler and electric switches) and let the system cool. This could take up to 5 hours but will make your job easier and will prevent you burning yourself.
4. After system is cool, turn off your AC water heater breaker. Breakers are located in your RV’s main electrical panel and look just like electrical breakers in a home
5. (optional) Turn off fuel source (propane or diesel), usually there is a shut off located near the Aqua-Hot unit itself
6. (optional) Remove 12v fuse from aqua-hot system  so that system is not error coding “low fluid” during the process. (We’ve always left our 12v fuse on during the process and have not had any issues)
7. Remove the Aqua-Hot system access panel cover by removing the 3 12mm bolts located on the top and front of the unit (see video)
8. Locate the antifreeze drain hose, it will be towards the bottom of the unit inside the access hole exposed by removing the panel. It will be the only hose that isn’t going back into the system and should have a red shutoff “ball valve” at the end.
9. Remove drain hose so that it is hanging out of front of system. Take special care not to turn the fluid release valve until you are ready! If you need to extend the drain hose to allow for draining you can use an adapter which will convert the Aqua-Hot drain hose to a standard garden hose size.
10. Get a suitable container to hold your old exhausted antifreeze fluid. We use plastic bins from Walmart as they have tops and are easily transportable to the dump when we are done (we put saran wrap over the top before putting the cover on the bin and drive slow). Whatever container you use it should be a minimum of 7-10 gallons.
11. Position the drain hose to drain into the bin, open the Aqua-Hot fill reservoir (clear plastic tank labeled Aqua-Hot near and above the Aqua-Hot boiler – you are opening so that it releases the vacuum in the system and fluid can drain more easily), double check your fittings are tight and drain the fluid by turning the ball valve at the end of the drain hose.
12. Allow the fluid to fully drain, go get a cup of coffee as it could take 10 minutes.
13. Close the ball valve and put the drain hose back where you originally found it in the system.
14. Follow the mixing chart on your antifreeze to mix the solution. If you are using Camco solution in the 1 gallon jugs, its a 1:1 ratio of antifreeze to distilled water. Pour one gallon of antifreeze for every one gallon of distilled water.
15. Use the transfer pump listed below to transfer the pre-mixed fluid from the 5 gallon bucket to the Aqua-Hot fill reservoir tank (see video). Take special care NOT TO OVERFILL the reservoir as the system will only take about 1/4-1/2 gallon of fluid at a time, then you must wait for the system to release the trapped air that is in the system. Air will bubble up into the reservoir where you are filling and the fluid levels will go down. Most systems will take between 5-7 gallons of fluid so be patient and take breaks if necessary.
16. Once you have filled the system and air bubbles are no longer coming out of the reservoir and the fluid level is hovering between the “COLD” and “HOT” labels on the fluid reservoir tank turn back on the Aqua-Hot in the following sequence. Replace 12V power (fuses), allow the system to boot up (wait 30 seconds), turn on 120V breaker inside your coach labeled “hot water heater” or similar.
17. Inspect your Aqua-Hot, verify the “low fluid cut off” light is not illuminated. If it is illuminated, add more fluid as necessary. Once the light turns off, proceed to next step.
18. Inspect system for leaks, verify drain valve isn’t leaking. Replace Aqua-Hot cover and screws securing cover. Take special care to seat the rubber grommet properly near the middle/top of the cover.
19. Turn on the Aqua-Hot Boiler using the Boiler switch on the black switch panel inside of your coach labeled “Aqua-Hot”
20. Turn on RV thermostat and set heat, adjust all zones to high temp to ensure heat is turned on in all zones. Baseboard heaters may take some time to turn on as the system needs to heat the new fluid, be patient as it may take up to 10 minutes before circulator pumps begin and fans in coach turn on.
21. Periodically inspect the fluid levels in the Aqua-Hot fill reservoir tank, as the system starts to circulate additional trapped air will be expelled and you will likely need to add more fluid. Keep doing so until system stabilizes and air bubbles stop bubbling in fill reservoir tank.
22. Replace fill reservoir cap and monitor system while heat is on for additional 30 minutes.
23. Take a towel or insulated glove and use the air release valve at the top of the Aqua-Hot to release any additional trapped air (see video)
24. Grab yourself a cocktail and sit back and relax, you did it and saved yourself a bunch of money while learning something very important about how to maintain your RV!

Materials List (amazon links)

• Camco Boiler Antifreeze 1 Gallon (6 pack 1:1 water ratio) http://amzn.to/2G7ycXq
• Camco Boiler Antifreeze 1 Gallon (single 1:1 water mix ratio) http://amzn.to/2FYKaiM
• Camco Boiler Antifreeze 32oz (concentrated 1:2 ratio) http://amzn.to/2FMntme
• Camco Transfer Hand Pump http://amzn.to/2HNGJvZ
• Adapter for extending your Aqua-Hot drain hose to a standard garden hose for draining fluid over longer distances http://amzn.to/2poc0ir
• 5 gallon bucket (CLEAN!) from home depot or another location. We find the Home Depot buckets are cheap and can be reused for RV washing.
• 10 ft garden hose extension http://amzn.to/2HK7th1 (very useful to extend the length of the transfer pump hoses depending on the layout of your system)
• Distilled Water – Available at most major drug stores and Walmart for less than $1.50 per gallon in most locations
• 12mm socket or cresent wrench to remove the 3 bolts holding on the system cover

Trust the Experts – Frequently Asked Questions & Answers from Aqua-Hot Manufacturer

Here is a link to Aqua-Hot’s website where you will find additional information and frequently asked questions about the Aqua-Hot systems.

• Aqua-Hot FAQ Link