Rusty water from the relief valve

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Ben17

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Hi,

I installed a new AO Smith electric water heater a month ago. When I opened the relief (T&P ) valve couple of weeks, the first burst of water coming through the valve is rusty (brown color). The water is clear afterwards. I checked it again after couple of days and this happens again. So far I have tried 3-4 times and it is always like this. What could be wrong?

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Ben
 

Sylvan

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The rust is from the T&P valve. Parts of it are steel. I have always have seen this rust.


There is NO "Steel" other then a stainless steel spring which does NOT RUST inside for a T&P ..

The lever to test the valves are ferrous metal but it does not come into contact with the water

It does not make sense to use ferrous metal that can rust and render the valve inoperative


The Spring is stainless steel and the body is bronze

Check out the ASME or the NBBI regarding safety or relief valves

Think about it

ASME Rated T&P Relief Valves

"Features • Thermostats with special protective coating • All bronze body • Stainless steel spring"

This is why someone servicing or installing a pressure vessel fired or unfired should at least have the basic knowledge of the ASME code
 
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Sylvan

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Thank you. Surprised that they use steel parts and not stainless steel


The manufactures would also be SHOCKED to find that someone had inadvertently used metal that can rust / deteriorate for a safety device.

This is especially true on hot water tanks as there is no other safety then the T&P the other are just an operating controller subject to failure unlike a boiler that has operating, safety devices and either a safety (steam) or a relief valve (hydronics)
 

Sylvan

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By the way tank like a boiler has a blow down valve that removed sediment and when just testing the T&P the minerals can work they way up to the T&P valve
 

Ben17

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By the way tank like a boiler has a blow down valve that removed sediment and when just testing the T&P the minerals can work they way up to the T&P valve

I do not think it is mineral. It is only the first few TSP of water that is rusty. It only happens if I leave it for few days apart. If try opening it in few hours apart I do not see this rusty water. I also tried opening the bottom drain and did not see anything other than mostly clear water.
 

Phog

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Inside the tank is a glass lining, which breaks down over time. Ultimately this is why your tank does not have an infinite lifetime. This breakdown process often (almost always) starts at the connection ports and expands outward from there. Where the glass has deteriorated, you start to get rust. You are probably seeing the initial stages of this process at the TPV port. It's not abnormal to see this, it's maybe a little soon for you but hard to say? Most people don't actuate their T&P ever, even once. You could call A.O. Smith and tell them what you see, to see if they want to do anything about it.
 

Jadnashua

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Did you use any galvanized pipe or fittings when installing the WH?
 

Jeff H Young

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Inside the tank is a glass lining, which breaks down over time. Ultimately this is why your tank does not have an infinite lifetime. This breakdown process often (almost always) starts at the connection ports and expands outward from there. Where the glass has deteriorated, you start to get rust. You are probably seeing the initial stages of this process at the TPV port. It's not abnormal to see this, it's maybe a little soon for you but hard to say? Most people don't actuate their T&P ever, even once. You could call A.O. Smith and tell them what you see, to see if they want to do anything about it.

We have no way of knowing the condition of the glass inside I kind of assume there are some defects from the day they are installed. pretty much agree the rust starts almost imediatly Just my gut feeling the top part of tank traps air as well and envirorment for rust.
 

Jadnashua

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It would be a lousy design if the WH trapped air at the top. The water pressure and flow when first used should purge it all out unless you've got a well pump with issues.

Depending on the water chemistry, you can get some outgassing with some anode rods, though. It's not oxygen, and that's what it takes to make rust.

The sacrificial anode significantly slows any rust degradation of the tank until it is eaten (sacrificed itself) away.

Potable water has dissolved oxygen in it, and that's the major culprit...iron and water can get along fine if you don't introduce oxygen into the mix.
 

Jeff H Young

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It would be a lousy design if the WH trapped air at the top. The water pressure and flow when first used should purge it all out unless you've got a well pump with issues.

Depending on the water chemistry, you can get some outgassing with some anode rods, though. It's not oxygen, and that's what it takes to make rust.

The sacrificial anode significantly slows any rust degradation of the tank until it is eaten (sacrificed itself) away.

Potable water has dissolved oxygen in it, and that's the major culprit...iron and water can get along fine if you don't introduce oxygen into the mix.
Jadnashua, do you think rust is from the anode? all water has oxygen so we know iron water and oxygen is there in his tank and all of them. maybe a small amount of rust is normal? air being trapped probebly not likely
 

Reach4

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A properly functioning anode should drive any iron ions back toward the tank rather than into the water. It's like a plating operation.

This thread has been useful in that I decided to see if I get rust from my T&P during a test. It would not operate for test. Does this probably indicate it would not open for a real over-pressure condition? Either way, I will replace it.
 

Jeff H Young

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A properly functioning anode should drive any iron ions back toward the tank rather than into the water. It's like a plating operation.

This thread has been useful in that I decided to see if I get rust from my T&P during a test. It would not operate for test. Does this probably indicate it would not open for a real over-pressure condition? Either way, I will replace it.
I couldnt guess whether it would open at 150 psi until it got that high. but if it wont work for test , I would have to assume for safety purposes that it would not.
I could google it but thank god the controlvalves on gas heaters almost never go into a full heat mode and if your not on a closed system pressure probebly never could reach that high. I dont know if an electric heater would be as likely to pop. Sort of a perfect storm senario
 

Reach4

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I hope it is not nearly as tight as my anode was. I can't get an impact wrench on the old T&P valve. I can get some torque by pushing on the galvanized out the side of the T&P. Add that to the wrench torque. Hope its enough.
 

Jeff H Young

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I hope it is not nearly as tight as my anode was. I can't get an impact wrench on the old T&P valve. I can get some torque by pushing on the galvanized out the side of the T&P. Add that to the wrench torque. Hope its enough.
youll get it tand p lot easier than anodes
 

Sylvan

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It would be a lousy design if the WH trapped air at the top. "



Actually if you look at most tanks the T&P is set within the upper most 6" of the tank meaning there could be an air spade near the top 6" of the tank .

Air is compressible and this is what make the tank dangerous


Also because of stacking the T&P Probe because of its location does not actually sense the actual temperature of the supply and neither does the aqua stat give a realistic temperate setting


Remember hot water rises and cold water is denser so it is much cooler at the bottom of the tank

The correct want to test the actual hot water supply is to set the aqua stat until it reaches the "set point" then open a faucet located near the water heater and take a temperature reading

The control valves are actually operating controls unlike a boiler that has operating and controls (high limit for example) and then a safety or relieve valves depending on the medium

When performing a hydro static test for example on a boiler or pressure vessel we isolate the vessel with shut off (king valve on boilers) valves and increase the water pressure and perform the Section IV (HLW) of the ASME pressure code normally at least 1.3 times the max rated working pressure test no less then 30 minutes up to 6 minutes or the NBBI code

All gauges must be calibrated prior to the test, Safety /relief valves either removed or gagged

On boilers to test the relief or safety valve we just cut out the high limit and fire the boiler and hopefully the safety will pop @15 PSI and a normal relieve valve will open at 30 PSI



 
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