Pressure testing cast iron radiators

JerseyJon

I mistakenly posted this in the Radiant Heat forum. I'm moving it here:



After months of obsessive searching on craigslist, I now have six HB Smith cast iron replacement beasts sitting on my porch. Before cleaning and painting them I want to pressure test them and assuming they pass, assess the fittings to see what needs to be replaced.

I am not a professional plumber. I've installed a couple of baseboard radiators so I'm not completely clueless, but close enough. I'm looking for some basic info on the steps to pressure test. I have a small compressor. I assume I need to plug or cap one end and somehow hook up a schrader valve on the other end. The plumber who brought my old system back to life had something like that in his bucket. I know there's some kind of steel fitting that I can solder copper to to connect the schrader to steel and then attach that to the radiator. Am I on the right track here?

Question 2: I read a post here that says water is better than air pressure. I'm not quite sure how I would do that. Maybe put a short piece of black pipe from one radiator fitting reaching above the top of the radiator, fill with water and pressurize the air at the top of the pipe? I have a regulator on the compressor and a tire gauge and can monitor air pressure. I don't have any way to regulate/monitor water pressure.

The radiators came from the first and second floors of a house that had a fire on the third floor. So they were used last winter and not likely damaged by the fire. I'm fairly confident they're good but want to double check.

Thanks in advance for any help.

For radiator fans: Five of the six radiators are unpainted and the one just has a thin layer of spray paint. Barely visible light rust. And they fairly well match the broken ones we hauled out last year. (25 inches tall instead of 28). If they don't leak, it'll be warmer in the house this winter and the odds that my wife doesn't kill me will increase significantly

hot_rod

one method

Start with a good flush, you may find mice of mud wasps have taken up residence inside. A garden hose from the bottom, then top to get all the crud out.



I use a Webstone valve with a 15 psi gauge, and a washer hose to connect to the hose bib.



Connect on the bottom connection, fill, cap off the top and take to 15 psi. You need to watch the pressure carefully, you can also add a Autofill set at 15 psi so you don't over-pressurize.



Once up to pressure, shut off the hose connection and watch the gauge for an hour.



This happens to be a 1" Webstone, 1/2" is fine.