Heating Help

Pressure Testing Radiators

What is the most effective way to pressure test old cast iron hot water radiators? I am installing a new hot water system in my house using salvaged radiators and would like to test each one before installing them. I was thinking of testing them using compressed air and a pressure gauge.
Thanks

Instead of air

use water. Leaks will show up much more easily. Vent all the air from the rad and run it up to 30 PSI. If it holds this pressure and doesn't leak for 15 minutes or so, it's OK.

Using water is safer too. If a bad section lets go, the resulting explosion from a rad filled with air can hurt someone. With water there isn't nearly the amount of explosive energy. But you still need to be careful!

Pressure testing

How are you pressurizing the water?

Can you,

pressurize-it from your incoming water pressure, but stop it at 30 PSI?
That`s a hydrostatic test.

You can compress air,, but not water!

just did this

converting a two pipe steam in a total house renovation job into hot water. Pulled out the guts in the traps, new trv valves on the supply, and new air vents. Pump everything up with air at 25 psi, (2x the working pressure on a hydronic system), left with air over night.
Seems ok. But I agree, if water is available a water test is just as good, or better.

Pressure Testing Radiators

I appreciate everyone's advice.  I understand the safety concerns, but I think I will try air pressure first.  I routinely work with 120psi air without any problems, so 25psi does not worry me at all. I can see water being more useful in determining the location of the leak, but soapy water could work for air.

Thanks everyone!

The air sometimes does not show any leaks

The water will show more of the leaks. Also remember when the radiators heat up to 180 degrees and 12 pounds leaks show that did not show at room temperature and 60 pounds of air pressure.

We'll see

I will only know for sure when filled with water, there's still the old supply and return pipes behind the plaster walls. Radiators are the least of my concerns.

Which is why

our company does not convert steam systems to hot-water.