So educate me then since I obviously dont know any better as you so eloquently said about my post? I appear to be somewhat confused or misinformed. I though marine water heaters were not that much different than house ones.
They can be similar or even made by the same companies.
House water heaters are made of solid stanless steel tanks inside?
No, the vast majority of water heaters are made of steel and then glass lined. The water heaters are very often the exact same even though they may say 6, 8 or 12 year warranty. The premium you pay for the 12 year warranty only covers the "insurance" for the warranty. Some may use a slightly thicker pressure vessel but that is really the only difference other than price.
There are some very high quality water heaters that are SS tanks but the vast majority are simple, cheap glass lined tanks.
Of course there are multiple types of water heaters:
Electric - Almost all are cheap glass lined products.
Gas - Most are still glass lined steel tanks
Oil - Again most are all glass lined steel
Indirect - These are almost always a SS tank though some are a glass lined.
*Indirect fired heaters are the most similar to a marine water heater.
Arent most of them lined with glass, ceramic or some polymer coating prevent the aluminium or stainless steel from contact with the water, to decrease the corosive effects?
Don't let them fool you the SS tanks deal with corrosion considerably better than glass lined steel this is why in the residential world they carry better warranties up to lifetime. The Crown Mega Stor on our house is 316SS and lifetime warranty. Compare a lifetime warranty or 15 years etc... on the tank vs. the 6, 8 or 12 of a glass lined steel tank.
Glass lined tanks must have anode rods. Most SS tanks, well made ones, do not. My mother had one of the first Super-Stor indirect fired water heaters in her house, as my dad was one of their first reps. The tank went in back in 1975 or so and is still going to this day. It has outlived two boilers and is in its 38th year of service. It is basically the same exact water heater as the Super-Stor marine tank only without the electric element. Her beach house has gas heat and a gas water heater. She is on her fifth glass lined tank since 1978 or about 7.6 years per water heater. The warranties on most glass lined tanks are worth the paper they are written on.
Especially considering our water is chlorinated. When I had to replace our house water heater a few years ago I thought they were all lined with glass or some polymer. the reason being they are less like like to resist the highly chlorinated water we use verus plain stainless or aluminum. I know about the anode and its purpose, but isnt stainless more subject to corrosion than glass?
Again a quality made heater will not have issues with this. 316L SS is highly resistant to corrosion.
My mothers old SuperStor is on city water. My Mega-Stor is on city water and zero issues. Over the years when I was a rep in the HVAC/hydronics market I sold a number of very high quality tanks and some cheap glass lined ones two. The RMA's I did on glass lined tanks took a good deal of time. I rarely, if ever did them, on the premium stainless tanks.
From a simple minded source Popular Mechanics
Water-heater tanks are made of steel. Steel that's in constant contact with water---especially hot water---will corrode quickly, so water-heater manufacturers usually line their tanks with glass.
Lining
Yes cheap steel tanks need a coating, no secret. In a home you have little worry of the outside of the tank rusting but on a boat at 80-95% RH the outside of the tank can rust a lot more rapidly. This glass however can develop micro cracks and the heater begins to rust anyway. This can be a cause of the smell people often complain about...
The lining consists of a thin layer of vitreous glass, bonded to the inside of the tank. As long as the lining is intact, the water can't begin to attack the steel.
Vulnerabilities
All true but even the tightening of a fitting by an unskilled installer can micro crack the coating and it will go unnoticed. The walls of these tanks are very thin and it does not take much reaming with a wrench to distort the metal enough to crack the brittle lining..
The lining may not completely cover all interior surfaces, however. The threads of bolts, for example, might have uncoated areas. Over time, chemicals, minerals and sediments in the water can cause the lining itself to break down.
Time Frame
Yep this is why they have such short warranties or you pay extra for the tank to insure/cover the warranty period..
Depending on the quality of the water and the quality of the tank, it could take decades for the lining to fail, or it could take only a few years.
Significance
Yep and lots barely make it out of the "pro-rated" warranty period which is usually not even worth the paper it is written on..
The most common reason for water-heater failure is lining breakdown.
Yep and SS tanks don't have brittle & rather fragile linings... It has always amused me that Raritan has sold this tank as a "premium" tank when glass lined tanks in the plumbing industry are known to be simply the cheapest possible option. Nothing "premium" about it. Cheap, easy to produce and good future replacement business.
Price out a sheet of mild steel and a sheet of 316SS than tell me the SuperStor or Isotemp are not TREMENDOUS values when compared to a Raritan.. Raritan is making HUGE margins on that tank compared to HTP or Isotemp..
To slow corrosion, glass-lined tanks have a magnesium or aluminum rod inside, known as a sacrificial anode. These metals are more reactive than steel; the rod's presence in the water creates an electrolytic reaction that causes it to corrode instead of the steel.
If glass lined tanks actually worked as designed, the lining protected the steel, they would not need anodes.
Think about it....
The anodes are band-aids there to protect a cheap product and hopefully get it through the warranty period.
Source:
Also how do you sanitize a hot water heater with bare SS as opposed to glass lined as bleach and any solution with sulfites will Attack the stainless steel/ aluminium?
I shock mine every spring and treat it throughout the year. Zero issues. A quality SS tank can survive city water easily and even the occasional shock treatment. Remember this is not cheap SS these are 316L stainless.....
Is what you are saying here is that what makes the Raritan inferior is the outer shell construction of the water heater, which is not made as well as say the Seward, or Isotherm. Is that correct?
No, I am talking all about the inner tank. The outside of the inner tank is bare steel, unless they have begun to powered coat them recently. The inside is coated with what amounts to porcelain. Ever seen a cheap porcelain sink made of thin steel? They made em and they all cracked. Cast iron sinks coated with porcelain are a different story because a cast iron sink does not flex. The "jacket" of these water heaters is only superficial and there to encapsulate the insulation. Most jackets these days are a non-corrosive plastic though the Isotemp is a beautiful SS jacket on the outside too..
Its not the tank itself as the tank being glass lined appears to be an advantage corrosian wise.
Again there is no advantage to a glass lined tank, only more potential for problems.
How are these water heaters made by Torrid, also glass lined.
http://www.marinewaterheaters.com/
Thanks for helping to reeducate me from my previous misconsceptions so that on my next purchase I have a more informed decision. I may still go with the cheaper model as overall it does seem to be cheaper over the long run, but in my final cruising boat I would like to put a heater in that will last as well as easy to maintain.
Dave
One only has to look as far as a company like Heat Transfer Products who produce both glass lined tanks and 316L SS tanks. Look for advice from a company that only produces glass lined products, and you'll get their self serving answers.
For example the indirect fired 316L SS water heater my mother has had in her house, virtually unchanged for 38 years, carries a limited LIFETIME warranty. HTP offers the same heater in a glass lined, less expensive version, and guess what...?? It gets a SEVEN year limited warranty.
The design is the same but the quality & price are different. HTP also "slush coats" their glass lined tanks and does not spray line them. To save costs many water heater manufacturers have gone to spraying the glass lining... Slush coating is arguably the best way to build a glass lined tank but still, it is an inferior product, when compared to a well built and engineered 316L tank. This is the same company producing both glass lined and 316L tanks and the 316L tanks have the better warranties because they are simply better built products which will last longer..
Having spent my early years an an HVAC/Hydronics rep, working for manufacturers of valves, boilers (both cast iron and steel), PEX tubing & radiant systems, fittings, control systems, air conditioning, furnaces, water heaters etc. etc.. you could not pay me to install a glass lined tank on my own boat. I was the guy doing the RMA authorizations on glass lined tanks, compared to the SS tanks I also sold.............. NO COMPARISON.....
You can certainly get lucky with any glass lined tank but it is sort of like roulette.
My choices would be:
Isotemp or Superstor or another 316L SS tank. After that a glass lined tank and as an absolute last choice any tank made with an aluminum pressure vessel/inner tank.
So at least a glass lined tank is better than something......
