Protech

Again, I can't see how the cpvc would hold while the tank deformed. Are you really going to tell me that the tank would go before the cpvc would due to over pressure/temp?

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TheMaster

I never saw anything said about cpvc on this thread until after I posted my 1st post.

Answer me how the cpvc will survive water hammer that will deform the tank from a sudden violent pressure surge vs a static pressure surge?

Protech

Simple, it has a better modulus of elasticity.

It would also withstand deep vacuum where the tank will not.


[quote=TheMaster;120838]I never saw anything said about cpvc on this thread until after I posted my 1st post.

Answer me how the cpvc will survive water hammer that will deform the tank from a sudden violent pressure surge vs a static pressure surge?[/quote]

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TheMaster

[quote=Protech;120839]Simple, it has a better modulus of elasticity.

It would also withstand deep vacuum where the tank will not.


The correct answer is it can be caused from thermal expansion and water hammer. Simple....as per your original reference to A.O. Smith technical bulletins both can cause the problem.

Protech

You asked "Answer me how the cpvc will survive water hammer that will deform the tank from a sudden violent pressure surge vs a static pressure surge?"

I answered: "Simple, it has a better modulus of elasticity."

THAT is the correct answer.

The cpvc (when new anyway) will withstand pressure cycling (water hammer) better than the steel tank will. The steel tank fails before the cpvc does.

I was also stating that the damage could have been from vacuum as well. The MIP’s would have been point out though (instead of in) if vacuum was the case I suspect.

[quote=TheMaster;120849]

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TheMaster

[quote=Protech;120858]You asked "Answer me how the cpvc will survive water hammer that will deform the tank from a sudden violent pressure surge vs a static pressure surge?"

I answered: "Simple, it has a better modulus of elasticity."

THAT is the correct answer.

The cpvc (when new anyway) will withstand pressure cycling (water hammer) better than the steel tank will. The steel tank fails before the cpvc does.

I was also stating that the damage could have been from vacuum as well. The MIP’s would have been point out though (instead of in) if vacuum was the case I suspect.

You'll never convince me that cpvc will hold up to serious water hammer and the water heater will fail everytime first.

Protech

Perhaps you should read up on material properties then. The cpvc is more elastic than the tank is. Each pressure wave will cause both the pipe and the heater swell as the wave spikes the pressure. The difference is that the cpvc will absorb the wave and bounce back where the tank will permanently deform slightly on each cycle.

Material will give to a certain degree and bounce back to it's original shape. It that deformation point is surpassed, the material will not return to it's original shape.

Think of a balloon. You can pump air into it and let it back out. It will return to it's original shape. If you pump too much into it, it will be slightly larger when it deflates. If you go even further, it will pop. The same is true for aluminum foil. If you made a sphere out of aluminum foil and piped it to the balloon they would both be pressurized to the same degree. If you were to repeatedly pressurize both of them, the foil would eventually fail because it will permanently deform on each cycle and the balloon won't.

Make's sense?

[quote=TheMaster;120866]

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TheMaster

[quote=Protech;120870]Perhaps you should read up on material properties then. The cpvc is more elastic than the tank is. Each pressure wave will cause both the pipe and the heater swell as the wave spikes the pressure. The difference is that the cpvc will absorb the wave and bounce back where the tank will permanently deform slightly on each cycle.

Material will give to a certain degree and bounce back to it's original shape. It that deformation point is surpassed, the material will not return to it's original shape.

Think of a balloon. You can pump air into it and let it back out. It will return to it's original shape. If you pump too much into it, it will be slightly larger when it deflates. If you go even further, it will pop. The same is true for aluminum foil. If you made a sphere out of aluminum foil and piped it to the balloon they would both be pressurized to the same degree. If you were to repeatedly pressurize both of them, the foil would eventually fail because it will permanently deform on each cycle and the balloon won't.

Make's sense?


Sure it would make sense in a Lab but not in a residental house. The pipe is gonna move and those stainless water supply lines you use will help relieve the surge. Thats why that cpvc broke behind the ice maker you posted pics of.....the crap gets brittle and then the water hammer will break it. I bet the water heater in that house was fine but that cpvc failed.

I was simply stating that deformed tanks can be caused by water hammer AND thermal expansion....then cpvc suddenly became the topic out of thin air

TheMaster

Here is a very informative link about plastic vs metal and water hammer. It seems that pvc/cpvc is so elastic that it only creates about 1/3 of the pressure surge as a metal system would. It appears to be so elastic that it deminishes the surge....When you get time read this entire page in the link.

http://www.docstoc.com/docs/22034422...cs-of-PVC-Pipe