Aqua Hot

[Steve Huber Co-Admin]

Dave,
George is right about the plastic tube going bad very quickly as the heat gets to it. I replaced mine with a rubber vacuum hose which give much longer life.

But, if it is only leaking when it's hot it may not be the hose from the expansion tank.Assuming the pressure  rating (13lbs) is correct, the new cap should be fine. The lack of a pressure relief lever does not impact the cap's functionality.  Check to see that the lip of the opening to the boiler tank is clean and smooth so you get a good seal with the radiator cap. When it leaks, can you see any wet areas areas?  

I suspect you are seeing more leakage after the cap replacement because the new cap is holding more pressure and thus forcing more fluid out the leak site when hot. If you can, pull the front and rear covers of the unit as that is where the leak is most likely occurring.
Steve

[David T. Richelderfer]

When I was at the Horn Rapids RV Park over the July 4th week the dripping was coming from that drip tube - from inside the tube or on the outside of the tube I didn't check.  I did not see any dripping from anywhere else, but the coach was level.  At home here I park the Coach on my driveway which is sloped downwards towards the street.  The coach is backed into the driveway so the fore end is lower than the aft end.  My air leveling will take out about half the slope, but it will not bring the front end quite high enough to make it level.  Here in my driveway the leaking is coming from two places - the dripping appears to be coming from both front corners - left and right - of the Aqua Hot box.  The dripping - remember, only when hot - is enough to leave two wet spots about one foot wide and five to seven feet long as gravity makes the dripped fluid flow downhill towards the street.

Replacing the tubing to the expansion tank is a good idea because this leak came on only in the past month that I am aware of, and it only leaks when hot and coming under pressure due to the heated fluid.  Also, removing the radiator cap and checking that the seal is clean and smooth is another good idea.  I think I will also pick up a 7 lb. radiator cap to see if that makes a difference in the amount of leaking.  I am thinking if there is a split elsewhere in a tube or fitting, then the lower pressure should reduce the amount on leaking.

I am at the end of a roof maintenance project and just started a bathroom remodel in my house, so have been using the motorhome shower (the other house bathroom has a tub, no shower)...  and there is no one around here that has the know-how to repair an Aqua Hot, as far as I know.  So...  I'm trying to get by with the coach's shower for a month or so.

[Frank Towle]

Thanks for all the great info on this system.  Two questions:

1.  What did you all use to adapt the rectangular output vent to round Gen-turi?  (photo would be great)

2.  As a very new (2 weeks) repeat owner of a Beaver, first time with Hydro-hot system - is it normal to spit what looks and feels like diesel fuel out of the vent or is this a leaky connection somewhere? 

Actually have a cake pan under the exhaust with about a pint or so of after four days in freezing weather.  Hope this is not normal and might have an easy fix.  I am handy with a wrench but know this system is fussy and don't want to mess it up.

[Orman Claxton]

Frank,
It is NOT normal for fuel to drip out the exhaust,
That is an indication of no flame,
Are you sure it is fuel dripping and not Coolant?

[Peter Chambliss]

I'm in North West Iowa and we have been below freezing for the last 10 days.  I have the coach plugged in to 50 amp and the thermostats set at 45 degrees with the diesel burner on.  So far the Aqua Hot has been doing a good job of keeping the temperature inside at 45 or above.  I have noticed that there has been some oily substance (small amount) that has dripped from the exhaust pipe.  I believe it is some unburned fuel residue that condenses in the exhaust pipe but not really sure.  It has gotten as low as 3 degrees and today it up to 25 so far.  It's supposed to get up to 40 on the weekend but we shall see.  Hopefully all will hold together until December 1st when we head for Palm Desert and weather that I'm used to.

[Gerald Farris]

Peter,
The small amount of residue that you are getting is probably water (a byproduct of diesel combustion) that is mixed with the soot in the exhaust, and it will freeze if you collect it and let it sit in freezing weather. However, if it does not freeze, it is probably coolant from a crack in the burner chamber because it is rare to have unburned diesel dripping from the exhaust if the burner is functioning. A cracked burner chamber is an expensive repair.

Gerald

[Peter Chambliss]

Thanks Gerald.  I'll try collecting it and see what I find.  Got my fingers crossed that everything keeps working the way it should in this cold weather!

[Edward Buker]

If you were unfortunate enough to have a cracked chamber it would leak readily into the combustion chamber under pressure and you should have ample steam generated creating some excess white exhaust. The real telltale would also be a continuing loss of antifreeze. I think Gerald is most likely right that it is a mix of soot and water condensation from the diesel by products of combustion.

 Roger Berke has a Forum on the Aquahot and Hydrohot systems that you may want to join also. I am in a discussion on that forum about how much soot or residue on the ground is normal. One of the first signs of a partially plugged nozzle is soot and or oily residue on the ground from unburned fuel. Roger has posted some photos. I am still trying to sort out normal residue vs a real issue based on the residue that I get.

Later Ed

[Peter Chambliss]

I checked again today and am pretty sure it is water and soot as Gerald said.  It seems frozen for the most part.  With the ongoing cold weather a fair amount of diesel is being burned.  As a side note, I added an anti gel additive to the fuel tank today since I had about 75 gallons of #2 diesel and 50 gallons of winter diesel in the tank. That should prevent problems until we leave on the 1st.  I got worried that if the diesel gelled the Aqua Hot would stop working along with the engine and generator.  Today is the first day above freezing in almost two weeks.  Up to 33 degrees!

[Joel Ashley]

Your evidence does indeed support Gerald's theory. 

My experience on several occasions in blizzard conditions and long icy spells in camp also backs it up.  The genset and hydronics exhaust pipes can be long.  Exposed under the coach to subzero temperatures, the pipes get very cold.  When warm exhaust heats up the ambient moisture in the air in the pipes, and it hits the cold interior pipe surface further down the pipe, it condenses out and begins running toward the end of the pipe, pushed along a bit by the exhaust flow.  Along the way from initial condensing to the pipe end, the water collects soot from the inside of the pipe, and it drips out looking like some sort of petroleum byproduct.

It's basically just dirty water, which is why you're seeing it freeze.  Nevertheless, it is good that you are alert to any apparent abnormalities and inquiring here.  Obviously from others' input here, there can be circumstances more serious behind noticed effluent.

Joel

[Frank Towle]

Thanks for all the extra input.  At 14 degrees F this morning, the liquid was definitely FROZEN leading me to belive I have an H2O leak in the boiler....  Have turned water pump and outside water (w/heat tape) off for now and will keep an I on the amount of water coming out of the exhaust port.

Looked up on aquahot.com and don't see that the boiler is a replaceable item, know it would be a job to swap out but everything else in unit is working just great. 

Any ideas?

[Edward Buker]

Frank,

The boiler, being filled with antifreeze, would need constant replenishment if you were leaking antifreeze. you have not mentioned having to do that. If your antifreeze is staying in the boiler then that is not your problem. All of the water plumbing uses tankless coils around the boiler and have no means of contacting or crossing into the boiler itself. Are you adding antifreeze all the time without a leak showing up under the aquahot?

Later Ed

[Orman Claxton]

Frank
If you have an internal water  leak, You will have water pouring out the coolant reserve tank,
BTW, have you added any coolant to the system?

[Orman Claxton]

Frank
After reading you earlier post ,I see you have a rectangular  exhaust, The liquid you see IS VAPOR

[David T. Richelderfer]

One of the bi-products of an oxidation-reduction chemical reaction is water, usually in the state of matter called vapor or gas.  The combustion process in the AquaHot whereby diesel is combined with air and ignited is an oxidation-reduction chemical reaction.  Therefore, there is a considerable quantity of water vapor made in the combustion process.  I have no idea what percentage of the diesel burned becomes vapor, but I expect that percentage to be quite high.  Given the length of exhaust pipe from the AquaHot's combustion chamber to the exit point I would guess almost all of the water vapor gets condensed into the state of matter called liquid.

In the case of your Beaver's big engine's combustion process there is much more vapor generated.  But due to the short exhaust pipe and abundance of heat keeping the exhaust pipe hot, the water vapor exits the pipe in its unchanged state, as vapor.  Thus you don't see liquid water dripping from that exhaust pipe... except perhaps immediately after starting the engine when the piping is cold.

As others have surmised here you likely do not have a coolant leak, nor a water leak, unless you are adding coolant or your water pump runs when it should not be running.  The water exiting your AquaHot exhaust is most probably simply water vapor condensed into liquid water in the exhaust pipe which is then forced along the exhaust pipe by the exhaust flow.