Blown hot water heater--ARGH!!

Cincy Aquaholic

Cincy Aquaholic

Active Member
Mar 15, 2009
1,329
Cincinnati
Boat Info
290 SS - 2016 Ford F250 Powerstroke
Engines
Twin 5.7 with Bravo 1's
Ok, I did not have a good first full weekend despite picture perfect weather.

Started with a dvd player that no longer reads a dvd.
Then, galley/shower sump pump float got stuck and flooded the sump area while admiral took a shower.
Then, my windlass up switch began acting up due to some crud on the wire contact.

THEN, we realize my bilge pump is running contantly under power. Bear in mind, I shop vac my entire bilge dry as a bone. Before we even got out of the marina its blowing water out the thru hull. WTF?!? :smt021

Could not find a leak anywhere until I cranked up the port engine while in the engine room and saw water POURING out from under the water heater. Port engine has the circulation through the tank. Ok, temporary fix was to pull the hose from the "in" on the heater and just return it to the engine to by pass the heater.

Ok, so obviously something busted and I assume its a winterization issue. Before I go off on my shop what happened here? Bear in mind I get NO leaks from the normal fresh water system even with the fresh water pump on. Can someone explain how the engine cycles water through?
 
Ok, you can all tear me a new butthole, but I see engine water running through a HWH as nothing but a problem waiting to happen.

CA, sorry to hear abt your woes. Consider it a shakedown cruise with some positive findings.
 
I agree! Just more hassle then its worth. Not sure I ever needed hot water when I wasn't dockside or running the genny. So, I'm obviously going to address this with my shop but wondering if I should just leave it as-is until this winter and deal with replacing it then. I just can't figure out why (and this is what I expect my shop to claim) if antifreeze was run through the engine how was this part of the system not winterized? Is there another way for it have busted?
 
I'm with Ron. That water is gonna be at 160 -170 degrees or whatever temp the motor runs as. Sounds like a good way to get scalded.

I am in the middle of replacing mine. Nothing too difficult. 4 screws hold it in. Just waiting for the paint to dry in the bilge before reinstalling.
 
I don't think scalding should be an issue because the engine water is just circulated through a heat exchanger and I doubt it heats that water much. Hopefully, someone will have some insight on how this could have busted. Unfortunately mine is a B!tch to get to and take out. I'm not even sure it will come out without removing the port engine exhaust riser.

This is from Atwood's website:

Safe and efficient heat exchangers
To quickly heat water when under power, Atwood has developed efficient heat exchangers. Each heat exchanger is specifically designed for the water heater's capacity resulting in heat up times superior to competitive models. These heat exchangers ensure safety by using a unique double tube construction which prevents any possibility of engine coolant contaminating the fresh water system
 
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Do you have to take it out? Why not just bypass it and plug up the HE. You probably have a 5 or 6 fallon HWH. If you run the generator for 10 minutes you'd heat up all 5 gallons sufficiently.

Rick, new boat like CA's may have anti-scald faucets.

Interesting thing is that during the heat of the summer and after a run, my bilge gets hot enough to make lukewarm water in the HWH, which is fine for a shower. I have an 11 gallon tank and 10 minutes on shore power and we're good to go.
 
Yeah, its by passed for now. But I still think if its a winterization issue my shop ought to replace it. I can't imagine it rusted out since its made of aluminum. I'll probably leave it for the summer and let them yank it over the winter.

On to the DVD problem . . .
 
The water circulating through the engine is 150-160 degrees. Hot water at our home is about 120 max. Scalding is definately a possibility at 150-160.

The engine coolant goes into the hwh, then through a tube (acting as a crude heat exchanger) that sits within the hwh thereby heating the tube and the surrounding water to 150-160.

With the engine's coolant lines currently disconnected will the hwh hold pressure or will water spray out into the bilge? (make sure you are not out of potable water in your storage tank)

I assume it will be unable to hold pressure so, just cap off the in and out fittings for the engine coolant on the hwh and rely solely on AC power to heat the water.

I also assume that your engine is closed cooled? If so, did antifreeze contaminate the hwh's water supply? You will want to flush the system well if that was the case.

I had a similar thing happen with an older boat, but it was raw water cooled (no antifreeze) and the water tube inside the hwh froze and cracked, but capping off the in and out lines still resulted in leaks. One of the fittings for the in/out's had apparently cracked, so I just had both fittings welded shut since I had no need for them once going AC only.

Hopefully yours can sucessfully be capped so you don't have to remove it from your ER (since it sounds difficult).
 
Never had one connected on a boat. Like Ron said, it's just another potential point of failure that isn't worth the risk. It's a heat exchanger- they develop leaks, often from corrosion, or bad/busted welds. Can't tell unless you tear it apart.
 
My 330 had the heat exchanger for the hot water tank on one motor and the cockpit heater/defogger on the other motor. To properly winterize the HWH and the heater core, the lines need to be removed and blown out, then A/F pumped through them. Just running A/F through the motors and hoping that it finds it's way to where it needs to be is risking a poor winterizing job.
Although, it may have rotted out. I would think the marina/dealer would know this, or the ball got dropped.
Our 360 doesn't have this "option" the ports are on the HWH for the hoses, but none there. The admiral misses not having the hot water after running the boat. If we are out at the beach for the day, upon returning to the dock, she washes dishes, and now has to start the gen or wait for the shore power, I just tell her to use cold water :grin:
 
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That stinks! I don't have anything to add, although I will definatly be checking this out when I fire up the boat. I've never liked that feature, it seems like a problem waiting to happen. I'll be bypassing mine.
 
Does anyone have access to and can post the procedure for winterizing the HWH? I don't have my documents with me and want to be able to discuss with shop.
 
Here's what I found in an Atwood manual...

WINTERIZING INSTRUCTIONS​
1. Turn off your main water supply, that is, your pump or
your water hook up source.
2. Drain your water heater inner tank. Upon doing so, you
will note that, due to the location of the drain plug,
approximately two quarts of water will remain in the
bottom of the tank. This water contains most of the
harmful corrosive particles. If while draining the unit, you
note that it is flowing sporadically or trickling, instead of
flowing steadily, we recommend one of two things. You
should first open your relief valve to allow air into the
tank and secondly, take a small gauge wire or coat
hanger device and prod through the drain opening to
eliminate any obstructions.
3. After thoroughly draining the tank, you should then flush
it with air pressure or fresh water. If you elect to use air
pressure, it may be applied either through the inlet or
outlet on the rear of the tank. It may also be applied
through the relief valve part. In this case, it will be
necessary to first remove the relief valve support flange.
In either case, with the drain valve open, the air pressure
will force the remaining water, along with the corrosive
particles, out of the unit. However, if air pressure is
unavailable, your unit can be flushed with fresh water.
Fresh water should be pumped into the tank either with
the assistance of the on-board pump or with the
assistance of external water either through the inlet or
outlet found on the rear or the relief valve coupling
located on the front of the unit. Continue this flushing
process for approximately five minutes allowing ample
time for the fresh water to agitate the stagnant water on
the bottom of the tank and thus forcing the deposits
through the drain opening.
4. Upon completion of the steps above, replace the drain
plug and the pressure-temperature relief valve.
5. After this procedure, there will be approximately two
quarts of water left at the bottom of the inner tank.
Should this water freeze it will not cause any splitting of​
the tank.


I drained my HWH, and removed the hoses from the engine and let those drain. I did not introduce any antifreeze to the HWH, I did put on a bypass kit though and put antifreeze in the water lines, then blew out everything that was left in there to avoid a bad tasting residue.
 
What I used to do to winterize the heat exchanger lines is to remove them from the engine, and introduce air to one hose and that pushes the water out of the other hose (it's a closed loop, this water does not mix with the fresh water system). then use a hand pump to pump A/F through untill it comes out the hose. hook back up to the motors...done
The instructions listed above from Atwood do not address the heat exchanger lines, only the tank.
To winterize the tank, I hook the hot and cold lines together(bypass) then open the drain, and open the relief valve by lifting the little lever and leaving it that way for the winter.
depending on how your relief valve is plumbed, you may need to take other precautions. On my 33, the tank was in the ER and the relief valve just spilled into the bilge..all set.
On my 360 the tank is under the midcabin sofa so it has a hose that exits overboard through a through hull...after the tank is empty I blow that line out..although it is supposedly not neccessary to do so.
 
I decided to send Atwood an email to see if they had any explanation for the cause of the failure other than what appears to be a winterization mistake. Here is the response: :huh:

Thank you for contacting Atwood Mobile Products, LLC.

The only thing I can think is that the antifreeze froze. They are not repairable. The unit will have to be replaced.
 
Frozen Antifreeze? Isn't that an oxymoron?

Replace it with an all-electric model and cut out the engine water flow.
 
I deleted the engine interconnect for the water heater when I did the major overhaul. As others have pointed out, I just see it as another opportunity for a serious failure. This one could be dangerous because even a small leak into the water system will contaminate the entire thing and possibly poison your family in the process.
 
I just removed my engine to water heater hoses and put a brass plug in the block. Water heater was leaking and we never used it...took it out.
 
Having a hot water tank is a pain in the you know what. Too much maintenance and then if you don't flush it regularly it smells bad. When mine goes out this is what it will be replaced with. I honestly don't know why these are not used on all cruisers where one would not be living aboard.

http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/56283/377%20710/0/water%20heater/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710&Ne=0&Ntt=water%20heater&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=0&Ns=0&keyword=water%20heater&isLTokenURL=true&storeNum=11&subdeptNum=27&classNum=28
 
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