Not at normal pressures with no head space.
For those that consider the 3/4 drain pipe improper, would you like it if it had a 1" drain pipe off the water heater safety pan?
Seems the pan would be irrelevant when steam comes out. ;-)
Very unlikely comming out af a WATER heater, now a boiler is a different story. 
Steam or water?
How it Works:
Water boils at 212° F when at sea level or under 14.7 psi of pressure, however, the boiling point increases when under pressure, which allows the** water to superheat beyond 212° F**. Typical residential water pressure ranges between 40 and 80 psi and at 50 psi, the water can reach 300° F.
Superheated water (now significantly above 212°F) would immediately return to atmospheric pressure (the boiling point of water is 212°F) and flash into steam, causing a sudden increase in volume and release of energy.
If the water in a water heater reaches a temperature of 210°F (before superheating occurs)** or** the water pressure exceeds 150 psi,** the TPR valve will open and release the overheated water.** This will allow cold water to enter, lowering the temperature of the water in the tank and consequently the water pressure. The valve will remain open as long as the temperature or pressure exceeds the preset limit.
If the TPR is functioning correctly it will discharge water. If it malfunctions and waits until the water has converted to steam you’ll probably have an airborne water heater. 
Exactly Chris,
Thank you for finding that.
This is a Code question that depends on your local plumbing code. Here it is acceptable. You must be able to see the air gap so that you know that there is a problem. Also many manufactures suggests that you test your TPRV yearly but we all know that they will stick on!
What about this setup, from today’s inspection. How is this different from going directly to the pan???
That is also a defect as it is not piped separately - write it up
Is that a condensate line at top?
Not to mention plastic pipe.
Wow, that’s so wrong - in so many awesome many ways.
It seems to be a condensate drainage pipe going downward through the insulation - yes? HA!
The plastic tubing is from a thermal control relief valve. CPVC is approved for TPR discharge pipes.
They had the thermal control valve, TPR valve, and pan all going to one indirect waste receptor. It was in the attic of a 3 story town home. There is not an easy solution. They’ll probably have to live with it.
Here’s an interesting find on the same water heater. I pulled back the insulation on the water pipe at the WH to see what type of piping was present…lookie what I found:
I thought I’d throw in the following:
Relief Valve Importance*
Water is essentially an incompressible solid. It has no latent heat energy within itself to expand when released, unless the water is superheated. Water above 212˚ F is superheated water, and superheated water would really like to turn into steam at atmospheric pressure. It possesses latent heat energy, which can flash into steam and create a force that is not unlike an explosion.
Water would normally boil at 212 ˚F, but inside a tank it can’t expand anywhere so it can’t boil off into steam. Water in a “closed” system and under pressure, such as inside a hot water tank, has a much higher boiling point. For example, where water supplied to a tank is at 50 psi, the boiling point is 297.7˚ F.
Let’s assume a water heater tank has 30 gallons of superheated water inside it. Assume 50 psi and the water temperature is superheated at 300 ˚F. Remember that superheated water really wants to turn into steam. If the tank ruptures, then 30 gallons of superheated water will instantaneously turn into steam in an outwards direction through the rupture.
There is a tremendous amount of energy released as the superheated water is exposed to atmospheric pressure and immediately turns into steam. Every cubic inch of water becomes a foot of steam!
Note that at 50 psi, water flashes into steam at 297.7˚ F, and the energy released equals more than 2 million foot-pounds of energy, similar to the explosive energy released by one pound of Nitroglycerin. A 16-inch gun on a USS Iowa class battleship produced a 7,500,000 foot-pounds of energy.
This is why it is essential to avoid excessively high water temperatures and pressures at a water heater tank.
- Excerpt from the course book included with the training course: Hot Water Tank Online Video Course (4 CE).
2007 Florida Code allows TPR discharge to pan
**[FONT=Times-Bold][size=2]P2803.6.1.1 Discharge. **[/size][/FONT][FONT=Times][size=2]The relief valve shall discharge
full size to a safe place of disposal such as the floor, water
heater pan, outside the building or an indirect waste
receptor. The discharge pipe shall not have any trapped
sections and shall have a visible air gap or air gap fitting
located in the same room as the water heater. The discharge
shall be installed in a manner that does not cause
personal injury to occupants in the immediate area or
structural damage to the building.
[/size][/FONT]
Just for information, all the water heater drain pans I have seen have a 1" drain connection.
That looks like a normal installation to me too!
After all, does anyone believe that when a TPR lets go, that a pan and outlet will take care of it? Think again. :)
In 25 years I have seen 2 TPR valves discharging. Neither discharged at full volume. It was like a puny spewing. The water heaters were in deplorable condition and I would have recommended replacement regardless of what the valve did.
The risk of water damage is insignificant compared to the problem at hand. Water damage is covered by home owners insurance.
The water heater itself poses the same unrestricted water flow potential as a TPR valve.
