21dv50 rheemglas rust in water

Replace water heater.
http://waterheatertimer.org/Leaking-water-heater.html
http://waterheatertimer.org/How-to-install-point-of-use-water-heater.html

Gene

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It may be what is called iron bacteria it will sometime grow in a water heater. It is present in some water and will actually thrive in water temps up to 120 degrees.if this is the case one solution is to increase the water tempurature of the heater to 130 -140 degrees this will kill the bacteria that is causing the rust problem.You Must install a tempering or mixing valve which will add cold water to temper or cool the water back to 120.
hope this helps.

Insinkerator stainless tank does not have anode rod to protect from rusting. So these water heaters rust out at welds. And must be replaced. And this is frequent problem.
Copy following link for installing under-counter water heater and see manuals for various models available. Non-insinkerator water heaters have anode rod to protect from rusting:
http://waterheatertimer.org/How-to-install-under-counter-water-heater.html
Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Copy following link for troubleshoot resources:
http://waterheatertimer.org/Leaking-water-heater.html

Replace rusted tank
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Prevent rusted tank.
If nipples are leaking, and they did not leak before, then tank has most likely rusted out and needs replacement.
Cause for rusted tank is depleted anode rod.
Inspect and replace anode each 1-3 years.
http://waterheatertimer.org/Replace-anode-rod.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

The warranty should not be void by using water softener, BUT read product manual.
http://waterheatertimer.org/Water-heater-manufacturers.html

1) First thing: Why is water heater leaking? Where is the leak?
http://waterheatertimer.org/Leaking-water-heater.html
For example, if you have electric water heater leaking from element, then replace element.
Replace leaking TP valve.
If water is leaking down vent pipe, and combustion chamber rusted out, then vent problem must be corrected.
These are not covered by warranty.
If tank is rusted out, then read below.

2) If water heater is rusted out after 4 years, you might have stray current corrosion.
This happens when hot and cold pipes are not connected together with a ground wire, and/or if cold water pipe is not grounded to earth.
This might not be covered by warranty.

3) Read water heater instruction manual for advisories.
Tanks rust out when anode rod is depleted. Softened water depletes anode rod faster.
Instruction manual says to check anode rod each year.
Checking anode rod is like checking oil on an engine. If oil was never checked and engine burned up, the manufacturer will not honor the warranty.
If anode rod is depleted, and tank is rusted out, the warranty might not cover the rusted tank since owner was supposed to check for anode depletion.

4) Anode rods can also be covered with calcium deposits and stop working.
This night not have anything to do with water softener, but anode stops working and tanks rusts out.
In any case the owner's manual probably says to check anode rod to prevent leaking from rusted tank
http://waterheatertimer.org/Replace-anode-rod.html

Rusted water usually means anode rod depleted and tank is rusting. Change 570241 anode rod every year or so.
Boiling water could mean bad thermostat causing run-away heating so water is released out of TP valve. Replace 994062 thermostat for 4 gallon.
Leaking water at TP valve could mean bad TP valve: replace TP valve with generic valve from hardware store.
Open link for diagram, parts and replacement information
http://waterheatertimer.org/pdf/Bosch-GL_English.pdf

The tank is rusting. Replace anode rod or replace water heater.
Once the anode rod depletes, then the tank starts to rust.
IF you can replace the anode rod, it will stop rusting, and then flush the rust out of water heater.
This might buy more life with same tank, but old anode rods are pretty solid and even impact wrench might not loosen it up.
http://waterheatertimer.org/Replace-anode-rod.html
http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html#flush

Loosen anode rod on new tank before installing, and then inspect every 1-3 years, and 1-2 years if water is softened.
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Anode rod is depleted and tank is rusting:
New anode rod will stop tank from additional rusting, but will not repair rust damage.
http://waterheatertimer.org/Replace-anode-rod.html

If rusting has been going on for a while, the steel tank could be weakened, and maybe rupture.
http://waterheatertimer.org/Water-heater-is-leaking.html

I suggest replacing water heater, loosening anode before install, and then checking anode rod each 2-5 years so tank last longer. Also add a ground wire between hot and cold pipes to avoid water heater deterioration from stray current.
Buy new water heater from local hardware or box store and offer 10% less than price, or have them install.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Add a comment for more free help.
Also take advantage of fixya expert assistance live.
For a price, expert works with you via while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Replace water heater, before it leaks on the floor
Rusted out inside

Your Reliance serial number shows your water heater was made in July 1994.

Except for the Marathon water heaters, and copper-tank water heaters, all tank-type water heaters are made of steel. That steel has an enamel coating which people call a glass liner.

So in that sense, there is a glass liner.
See a photo of the liner:
http://waterheatertimer.org/images/Enamel-coated-steel-290.jpg

Also inside the tank is an anode rode.
The anode is made to protect the steel tank.
Anode is made from lower noble metal than steel, so water reacts with the lower noble metal first.
The water eats away the anode rod instead of rusting the tank.
Once the anode rod is gone, the water begins rusting the tank.
The enamel coating does not protect the steel from rusting.
The tank rusts away and begins to leak.
http://www.thisoldhouse.com/toh/video/0,,20047047,00.html
http://waterheatertimer.org/Replace-anode-rod.html
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html