Radiator vent location

David Hohengasser

I bought a used Burnham Slenderized raidiator that was used for hot water. The coin vent tapping is at the top. Can I use this hole for my steam vent, or do I need to drill and tap a hole on the bump out in the casting that is about halfway up?

Brad White_63

Halfway up for steam.

Top vent for air (air rises within water of course), but steam is a gas and seeks low pressure wherever it is. So yes, tap the mid-height dimple.

If you placed the vent in the water tapping, the steam would seek it but the radiator would not fill with steam all the way; the corner opposite the valve might be "ignored". You will get some heat, just not near full capacity. You are paying for 100%

Tip for you when tapping: Use the appropriate size pilot and tap of course, with plenty of oil. But when tapping, do not back out to clear the chips as you might with steel. Keep going in the same forward direction until you are done. The CI grain structure is such that the threads you just cut might break off or round-off when you reverse. Only reverse once you are all the way in. ShopVac the crumbs and you are done.