Main Vent Air Valves vs Automatic air release valves

PolandOhioBoiler

It appears that I have 3 old Air Release Valves….Any idea if they would be 1/4" or 1/8"? would like to order and have them ready when I shut down the system.

The gas hot water boiler system is original from late 1950's and heats a 2 story 3000sf home.

Then there is a 4th valve that looks different. Is this a "Main vent valve"? Can I replace it with a typical automatic air valve like this? :

https://www.supplyhouse.com/Resideo-FV180A-1-4-NPT-Float-Type-Automatic-Air-Vent-150-PSI-240F?utm_source=google_ad&utm_medium=Shopping_Heating&utm_campaign=Shopping_X_Heating_X_SSC_ClassA&utm_campaignid=21633352233&utm_adgroupid=170415967390&utm_targetid=pla-2352613557038&utm_product_id=FV180A&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Heating&gad_source=1&gclid=CjwKCAiArKW-BhAzEiwAZhWsIFNtd3hMQe6wUxowI2fqwzIFpenpWGBRl2DmM4-fLrPulWkaVvfurRoCiXMQAvD_BwE

A parts list for the 4 vents would be fantastic (if possible to tell from photos). Thanks everyone….total novice here.

tcassano87

top 3/4”

other 2 look like 1/8th”

hot_rod

You could buy 4- 1/8" and a handful of brass bushings, try to standardize the vents.

3/4 X 1/8 bushing

1/4 x 1/8 bushing

A vent with a service valve is handy also for future service.

PolandOhioBoiler

Thanks so much….Great Idea regarding the bushings. I just didn't know if that "4th" larger vent had different functionality than the other's. Sounds like they all do the exact same thing, only different size threads, correct? Appreciate it!

hot_rod

They are all float type air vents. Mainly used on high points in a system.

They do come in different thread sizes and capacities. If you had a part number you could determine the exact spec on them. The ones I show or other similar brands will do the job for you.

Ideally there would be a central air purger back near the boiler to help remove air as it circulates around the system. This shows how different air removal devices work in a system. Air separator or purger at the boiler, auto vents at the high point.

PolandOhioBoiler

excellent information. Much Thanks Bob! Caleffi air valves on the way. I'll post if I need further assistance.

EBEBRATT-Ed

Assuming this is HW the first picture looks like a steam vent.

RTW

You could boil the vents in white vinegar first (for 5 or more minutes), to see if that fixes them. Newer valves seem to be of less quality and have a fraction of the life span. Ive done it with older quality vents with excellent results. Others more experience on this site can suggest how best to remove them as well

All the best,

RTW