I have a baseboard hot water (hydronic) heating system. I've noticed for a while that my well pump kicks in at odd times when there's no water running anywhere in the house. Now I see there's a fitting on top of my expansion tank that is leaking. I think it's an air purge valve, but I'm not sure. I suspect what's happening is that the boiler system is calling for replacement water.





Questions:

1. What is this valve called?

2. I'm assuming I can replace it myself. Shut off the boiler, shut off the water supply to the boiler, bleed off the pressure and swap the fitting. Am I missing anything?

3. If #2 is reasonable, what's the best way to bleed off the water pressure?

4. Once replaced, do I need to "burp" the air out of the system and if so how?

I believe that's a Vacuum Break(er).

Here's a pretty good video re: purging/'burping' air from Hydronic Heating Systems:

https://www.youtube.com/watch?v=KZI7_UJI5LM

The presentation isn't the most professional, but he knows what he's talking about and explains things well. I have a boiler/hydronic heating system and have watched his videos before, including re: a Taco 007 Circulator issue I was having on the coldest day of the/this year! He seems like a 'regular guy' and, as did I, you'll probably appreciate his approach/delivery.

Unless you've got a wet mess on the floor and/or are concerned of a catastrophic failure, I'd probably wait and just throw a bucket under it for now. You can monitor it to determine the severity, and if possible, wait until after the winter to address your issue. Just sayin'...Good Luck!

ETA - Now that a 'pro' has responded, apparently that's NOT a Vacuum Break(er). Interesting...Apparently I have one of those hidden up in the insulation between the floor joists! Good to know...

The device on top ( brass ) is a auto vent. Should be able to pick up locally ( HD / Lowes and such ) You're correct with the depressurization, valve off the make up, open the boiler drain till pressure is basically zero ( no need to allow the flow from the drain to stop and pull in air, as the auto vent is above the drain and will be at a lower pressure and even a slight vacuum if the drain is at 0 psig ) ) Replace auto vent and open the make up. The auto vent should take care of the bleeding of any air. If you introduce alot, go to the high point of the system and look for a manual vent once system pressure is back to normal ( typically 12 psig ) 12 psig is standard makeup valve setting for a 2 story residence.
I note, the area below the auto vent appears dry. Intermittent well pump start with no normal usage may be due to a leak elsewhere.
When was the last time you checked your Extol well system tank? Its possible that the bladder pressure is too low and needs air added to the proper setting ( typically set at the or just below the cut in pressure ). If the pressure is too low or gone, the pump will loose pressure rapidly and cause a sort of short cycling.

Thanks much for the replies!

For hvactech: I discovered the problem due to a puddle of water on top of the boiler. I cleaned it up and put a bowl under the expansion tank (water runs from vent down the side of the tank) and collected about a cup of water within 24 hours.

Bladder tank on the well is new within the last 4-5 years. Pump is not cycling as soon as I turn on a tap which is the usual symptom of a waterlogged bladder based on past experience. I will double-check tho.

PHPaul, I forgot to mention, on top of the auto vent is a cap over the vent port, you can hand tighten it and this will close it off, stopping the leak until you obtain a replacement.

quote:

Originally posted by hvactech:
PHPaul, I forgot to mention, on top of the auto vent is a cap over the vent port, you can hand tighten it and this will close it off, stopping the leak until you obtain a replacement.

Thanks! Hope to get one at Deep Homo Monday.

Since you're not familiar with boiler systems, I'd recommend you hire a professional or wait until warmer weather.

Ending up with an air locked system and not knowing how to resolve it will not be fun when your home becomes cold.

Afterall, when was the last time the system was serviced?
Expansion tank pressure checked/set, fill pressure checked/set, relief valve checked, burner cleaning, checking/adjusting fuel pressures, checking carbon monoxide levels, combustion testing, insuring the integrity of the venting system, etc.