Atwood 6 Gal water heater woes

[gaugeguy]

As I struggle along to restore our 1975 Minnie Winnie, I noted the water heater had both the cold inlet and hot outlet fittings removed from the tank. It was essentially by-passed by the rest of the water lines.
I don't know if it leaked inside the tank, or if one of the inlet/outlet fittings was cracked. One of the previous owners simply eliminated the tank from the system.
In any case, I removed the heater and took the entire thing apart.
I cannot find a leak, split, crack or pinhole anywhere on the darn thing.
Now, I not certain exactly how this thing works but it is an ancient model G6A2, gas only with pilot light.
I guess my basic question is how does one go about testing the tank. There are six holes in it. 4 are water for fittings and two are rather large openings where it appears one end for the pilot light and the other end comes out as a vent; so it is a single tube.
I can plug off the water holes and put some pressure to the tank. I assume there should be no water coming from anywhere.
Is it possible there is a crack in the pilot light/vent tube? Should there be any water appearing in the vent tube?
Can a radiator shop clean and fix these?
Do any of you knowledgeable folks out there have any experience repairing these units.
Anything helps!

[Ray,IN]

I've never attempted a repair, but I know how to pressure test the tank. Only use water, do not use air pressure! Buy some adapters so you can hook up a garden hose to both fittings, then place the tank in-line with the hoses, and put a hose sprayer on the end (closed) so when you turn on the water everything is pressurized.
If the tank is corroded and either leaks now or the water pressure creates a pinhole, it's not repairable. The reason? If corrosion created one leak, others will quickly follow. If you really, really want to keep the original tank, yes, a radiator repair shop will be your best choice.

[mahon1993]

You should have three water fittings. One cold inlet, one hot out and one for a pressure relief valve. You could put a plug in two of them and a fitting for a water hose in the last one and apply water pressure to it and look for leaks. If the tank is aluminum it could probably be repaired. If it is steel and leaks it's probably rusted and not repairable. I had one that developed a leak up in where the gas burner goes. I was able to reach it and clean it a repair it. It was a steel tank. I would suspect your tank was bypassed because it leaked. Why else?
Greg

[RV Wizard]

If there was no by-pass for the water heater for winterizing; I surmise it was manually by-passed to do so. If it were me, I would install a new auto ignition unit in, since you have it out. Not just because of its age but just the ease of use.

[Shadowcatche]

Leak testing should use air not water, and just use a soapy solution sprayed around the openings and the tank. Do NOT over pressurize the tank and typical water utility is about 60 PSI to 80 PSI. Why air rather than water, because it will be less likely to harm the tank and it is easier to find leaks and this is how leak testing is done in an industrial setting.
If the tank froze at some point and/or cracked it can be TIG welded by a competent welder. Aluminum has a finite modulus of elasticity and is subject to cracking.
When I was in having the aluminum frame reinforced on our teardrop trailer I noted they were welding an Atwood water heater tank which froze and burst (not winterized/drained) and evidently this is a fairly frequent job for the shop.

[Dave78Chief]

This is the current base manual for a Atwood Pilot Model Water Heater: http://www.atwoodmobile.com/manuals/...2011.19.07.pdf

This is the Atwood Trouble shooting manual for both Pilot and DSI style Water Heaters: http://manuals.adventurerv.net/Atwoo...er-Service.pdf

Pressure testing is a 2 step process. Both cold and hot. It can be ok at normal cold water pressure (45-60psi max) but leak when at operating temp. The pressure relief valve is rated at 125-150psi. For a pilot model, there are at least 5 water fittings that enter the tank:
1. Cold water in (on rear).
2. Hot water out (on rear).
3. Pressure relief valve (on front)
4. Drain (on front)
5. Gas valve Thermocouple (senses water temp for shut down; N/A for DSI model)

When pressure testing, I would make sure the Pressure relief valve, Drain plug, and gas valve are installed. You want to know if they are leaking. Be sure and read the information about presssure valve weeping. It is not necessarily a leak per-say and in many instances can be corrected by re-establishing the air pocket expansion at the top of the tank.

The LP Gas portion is a seperate independent circuit. If water is seeping out from the larger gas piping then there is an internal leak. I doubt that could be welded (no access). The only direct inter-reation between the LP side and the water side is the thermocouple portion of the gas valve.

Dave

[frankdamp]

Having a pilot light is a PITA, particularly when you're out in the rain and the wind trying to get it lit, with that outer cover at risk of blowing away in the dark! I think I'd go for a replacement current model 6-gallon unit with direct spark ignition, but I haven't priced one. My rig has a 6 gallon Suburban DSI/electric unit.

[Batman_777]

I had a tank leak on an Atwood 10 gallon Gas/Elec. The tank is oval aluminum in two halves like a plastic Easter egg. The welded seam down the middle can get pin holes that are only seen when pressurized or you might see something that looks like water hardness around the seam. Look for the residue near the weld seam.

[gaugeguy]

Well, it's a bust!
I used 40 psi of air pressure and plugged off all the holes. I didn't need soap.
There were numerous pin-hole leaks around the tank cold water inlet. They were all in an area about 8 square inches. Each leak spit out rust and corrosion along with the air. I suspect the area is pretty thin by now.
So the tank is trash, but I learned other things, too.
One guy I know who repairs aluminum radiators told me to never screw any steel components into aluminum. He said to either use brass (which tends to break under stress) or stainless steel. It appears they don't react as intensely with the aluminum as steel does.
Thanks, folks, for all your help in this matter. I guess I'll have to save up for a new one!
GP

[frankdamp]

Good decision, GP. Now you have to decide whether to add the wiring for AC opertion! After a season and a half, I'm still not sure about electric heat. In theory, it should be a real money saver if you're at a CG with un-metered power. It also should give you a much quicker recovery when you take a shower.

I can't tell, if I have both propane and electric on, whether the electric element is adding to the heating rate.

Several times, when switching to eletric, I've popped the 30A CB on the CG pedestal. I'm still trying to figure out if I have a high power heater or a short circuit. I only have a 15A supply at home, and even with nothing else on, the electric water heater still blows the breaker. It shouldn't, as the heater is only supposed to pull 12A.

A winter investigation is needed! I'm trying to find out what the resistance of the element is supposed to be when it's cold, but nobody has responded.

[Dave78Chief]

The electric element is a resistive device so it is a simple matter of ohms law. 120 / 12 = 10 ohms. The Atwood service manual only says you should have continuity. The installation manual lists it at 1500 Watts which is 1500 / 120 = 12.5 amps (120 /12.5 = 9.6 ohms).

Dave

[GMRHost]

I had one of those older atwood water heaters, and the regulator/pilot light assembly started blowing flames the wrong direction. It's history.
After shopping for RV water heaters, I found it more cost efficient to install a tankless heater. It runs on LP, I never run out of hot water, and there is no start-up waiting time. The brand-new unit cost me 400 at the time, and a new Atwood's unit would have been about 360. For me, it was a no-brainer, and even easier to install.
I have another vintage unit, now, and it will get a tankless heater as well. I'm sold on them, and I even have one I purchased that is piezo-electric start, so I can even use it economically boondocking.
Just my 2 cents worth! Hope you find what you are hoping for!