Colgar

It does seem like there is more to it than that, doesn't it?

To me, it raises more questions than answers.

TheMaster

What else could there be to it? They said a storage vessel,that means any size to me.....Water is constant and the only variable is the pressure at 50 psi and they specify the temp rise at 10 degrees. Piping has nothing to do with their statement,they said a vessel. Its a hypothetical.....and i bet they are not considering the vessel will expand for their statement to hold true. Thats the way i read it. Sombody call them and clear it up so i can sleep again

Colgar

That's knda how I took it also.

But- I would like to know the math behind it.

Does a cup of water in a closed vessel @ 50 psi increase to 250 psi with a 10 degree rise? In other words, does the volume of water being heated make a difference? The starting pressure before heating? In my mind no, it doesn't matter, but I don't know.

As soon as I feel like banging my head against the wall, I call them for more info.

Protech

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Protech

That's why a valve is better than a tank

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TheMaster

It fails safe....hopefully. Thats not for certain. Relief valves can fail from corrosion and fail to function.
You cannot get a perfect constant 80psi either like a tank will provide...you hafta set it high or it WILL leak prematurely or possibly leak too much.
Too much fiddling and adjusting,tank you set the pressure and its done.
Your loosing water,even tho its not much.
Ultimately I will fail you based on code....your exceeding 80psi.
My problem with the tanks are that they fail and they can fail and flood the house. if you read on the tanks it says install in a location that rupture cannot cause property damage.....well where would that be other than outside or in a crawlspace?
What good is installing a water heater pan when you have a 3.5 or 5 gal tank above it all that will not leak into the pan but spray all over the room?
Maybe the best way is a tank located where it cannot flood and do damage or a housing that encloses the tank with a drain to the pan AND a back up relief valve set at 100psi to take over in the event the tank fails like your using..

futz

I've been using these Apollo 78-325RV (EXV) combination ball valve w/thermal expansion valves for thermal expansion. They're factory set for 80PSI relief (it's what the inspectors here demand), but I sometimes boost that a bit (as Protech did in the video) to keep them from constantly dribbling when customers have their PRV set high.



The photo shows barbs for vinyl or other soft tubing. The model # I use (78-325RV) has a pex barb outlet.

Though I don't have hard water problems here, I'm still not terribly thrilled with them, but the alternative is expansion tanks. I don't like tanks for some of the reasons stated previously by others in this thread, so expansion valves it is.

Protech

My beef with tanks is you get 5-8 years out of them and then the bladder goes. No one will know when it does. Then you high pressure due to thermal expansion and somthing may let go and flod the place.

As far as corrosion goes, I don't think it's very likely as it isn't installed on the steel tank like the T/P.

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ChrisConnor

Can you just replace the thermal expansion valve or do you have to replace the entire ball valve?

futz

If one failed (I guess it'll happen eventually) I would just spin out the thermal valve and crank in a new one. If I couldn't buy the thermal valve by itself I guess I'd just buy a whole valve, steal the thermal valve and toss the ball valve in the scrap bin. I suspect that replacement thermal valves are or will be available though - haven't checked. Thermal expansion protection has only been a code rule here for a few years now.