Hello,
The Taco Hy-vent on top of my expansion tank is leaking (slow drip) from the screw cap located on the top of the vent (cap has a slit on the side of it).
I checked the boiler because I hear a gurgling/bubbling sound through my forced hot water baseboard.
The screw cap on top is not tightened firm.
Please advise on necessary measures to repair and/or replace the hy-vent to stop the leak.
Thank you!

 

The Hy-vent leaking may not be the source of your problem. It may need to be serviced (replaced), but possibly not the cause of the air in the system. It's supposed to take air OUT, and the cap should not be screwed down tight. You CAN screw the cap down to stop it from leaking, but normal operation it's supposed to be open to let any air it catches out.

It should just simply unscrew from the top of the air scoop. You need to reduce boiler pressure to zero before you remove it, and if you can tolerate some spilled water, you shouldn't have to drain the system first. You may get wet. THAT WATER MAY BE HOT ! Best to wait until the system is cool! To not spill water, you would have to drain the system enough that you can remove the hy-vent without water behind it, but then you are faced with the job of purging all the air from the pipes, and that can be a pain. Look around and see if there are any valves that can be closed to isolate the section of piping with the hy-vent on it. If you can find these, you only need to de-pressurize that section.

Put a bucket under it until spring time. (it's almost here!)

Where is the air in your system coming from ? That's the real question here.

It is possible that the hy-vent is leaking enough that fresh water entering the system (from the automatic water feeder) is releasing air when it's heated.

What is the pressure on the boiler gauge, at what temperature ?

Do you have any other leaks ?

 

Thank you (NJ Trooper) for your excellent response. I checked the (in-line) water filter which is directly off our fresh water (well water) inlet and it needed changing. Maybe a dirty filter creates a vacuum?
The pressure/temp. gauge on the front of the boiler shows only 2-3 psi. @ 180F. The system has two zones, one for the basement level and the second for the second floor (small ranch style home).
If I need to clean/replace the vent, I have ball valves all over the boiler piping system so draining the system shouldn't have to be done.
Question: How much pressure should the expansion tank have on it?? I checked it w/ a tire pressure gauge and it doesn't register a pressure.
Thanks again,
Rick

 

Rick, your first problem is the system pressure. It should be around 12-15 PSI when the system is cold, and rise maybe 5-8 PSI or so when hot. Never more than 27 PSI.

Check around for signs of leakage... greenish/white deposits around the elbows, and valves are a clue. When the pipes are hot, and the leak is slow, the water can evaporate as soon as it leaks, so you end up with deposits instead of puddles.

It's possible that the hy-vent leaking like that over time has drained the pressure from your system, and your automatic filler may be crudded up and not working (or a valve may be shut off?). This auto filler is a bell shaped thingy in line with the supply (and hopefully _after_ your in-line filter ... (I suffer from well water also, I know your pain) )

You can only get an accurate check of the pressure in the expansion tank if the water side pressure is at ZERO. With the water side at zero, you need to put around 12 PSI on the air side. The pressure on the air side is supposed to match the normal system pressure when the system is cold.

Do you get any water out the air valve when you "blip" it ? If so, the tank needs to be replaced.

You need to do a few things:

Find the fill valve / pressure regulator / anti-backflow device in the fill line. Figure out why they aren't maintaining around 12-15 PSI in the boiler.

Determine if your expansion tank is good/bad, and either adjust the air pressure, or replace the tank. If the expansion tank is like 10 years old, just plan on replacing it, they're relatively cheap, and easy to change. If you do change it, BE CAREFUL! it may be full of water, and a LOT heavier than you expect it to be! The new one will be very light! Don't expect the installed one to be the same! Have a helper at the ready.

If you can post some digipics on www.photobucket.com and provide a link here, it will help to tell you what to look at...

 

Thank you...I think I've got it.
I replaced the hy-vent air vent and purged both zones of air.
It seems to be working fine w/ proper pressure, etc..
I appreciate your advice!
Rick

 

Rick, what did you do with the zero pressure in the expansion tank ? I hope you put some air in that !