automatic air vent leaking and sticking

tset

Hey there, after a few years my Caleffi 556 automatic air vent either leaks water, or fails to vent air unless the needle valve is manually depressed. My New England water deposits minerals fairly quick, but they are quickly dissolved with vinegar. No water additives are used, all copper piping, 30 year old Burnham steel boiler with the big 3 inch tubes through the water tank. Domestic hot water coil, but sometimes I switch to an electric hot water heater for weeks/months and leave the boiler off. Annual flushing produces black water.

I scraped off the needle valve, looks like maybe O ring rubber deposited on needle valve taper. This time I added O ring grease (Toyota high temperature disc brake caliper O ring grease); now the vent doesn't leak water, but has to be manually pushed and then the air is vented.

I am replacing the cap/vent valve assembly. Should I grease the vent valve O ring and tapered needle valve to try to get a longer life? What kind of grease? Plumber/silicone grease? I'd like to be able to just replace the O ring and needle valve rather than buying $50 cap/vent valves.

Regards

hot_rod

I think any grease would make the needle attract dirt and debris and possibly stick the needle to the seat?

I believe it is EPDM, which is not an oil or grease tolerant rubber

Anyway to clean the system, add filtered water and a conditioner?  Sounds like your fluid quality is causing problems. At least consider adding a conditioner, they lock up the minerals in the water and help prevent scale formation. Is there a leak allowing fresh water into the system?
Also at some point the system should be pretty much air free and the vent is not cycling.

Lastly do not push down the schrader valve to expel air. That vent is designed to maintain a 1/2” air space at top to keep fluid away from the valve mechanism. When you bleed that air manually, you pull the crud up into the valve.

tset

oh that is interesting; didn't know there should be a remnant of air on top. So air coming out upon manually pressing the valve does not indicate that the valve was not properly venting. The system did very well for 4 years with the 556; since there is very little air/noise now, and the valve is not leaking, maybe I should just leave it alone and see if no air/noise or water leak problem develops.

EdTheHeaterMan

This falls under the "if it ain't broke, don't fix it" department.

hot_rod

Any of any of the micro bubble type air purgers should leave you with an air free and quiet systems within hours or days once all the fluid has passed through.
If air noise persists, look for where it could be entering. Pumping towards an expansion tank can set you up for air ingress. An under pressurized system can.
non barrier tubing can also