Air Separator Valve Leakage

Old 04-21-11, 08:43 AM
Thread Starter
Join Date: Feb 2011
Location: us
Posts: 28
Upvotes: 0
Received 0 Upvotes on 0 Posts
Air Separator Valve Leakage


Here are the pictures:

Above is my heating setup. If I am correct, the valve above the small tank is called an air separator valve.

I believe that it leaks from the red knob on the top of it at a rate approximately 5gal in two days. If I unwind the knob, it leaks faster, probably twice as fast.

My questions are:

1. Is it possible to fix it?

2. If the answer to the above is "no", can you provide me with step-by-step procedure how to replace it?

No plumbing experience here, but very handy and have access to various tools.

Thank you very much in advance

Old 04-21-11, 01:59 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 15,984
Received 79 Upvotes on 71 Posts
Hi yes you can replace.

Get a new air vent. And wrap 2 turns of teflon tape clockwise with the threads pointing to the right.

Turn off electrical power to the boiler. Let the boiler cool to 100F or less. Boiler water can scald if you do not let it cool.

Shut off that blue valve all the way to the right in pic #2

Shut the two yellow valves on the lines left of the air vent in pic #1

Shut the blue valve with the big yellow tag above the circ.

Drain some water out of the boiler from the boiler drain that should be under the circulator, until the pressure reads 0 psi on the boiler gauge.

Replace air vent. You will get some water probably but not alot. Have some towels handy or a bucket.

While you are at this point check the air in the expansion tank below the ait seperator. Check with a tire gauge. It needs to be 12 psi. If less, add ait with a bike pump. If water comes out of the shrader valve replace the tank.

When all is done open all the valves in reverse order as described above.

The pressure on the gauge should rise to 12 psi and stop.

If all is good, turn the power back on, and turn both zones/t stats up/on.

Make sure the air vent cap stays loose. Only air shoul come out.

Any issues with the above post back here.

Good luck.

Mike NJ
Old 04-21-11, 05:18 PM
NJT's Avatar
NJT is offline
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
wrap 2 turns of teflon tape clockwise with the threads
Keep the teflon tape at least 2-3 threads away from the end of the threads. And on that fine thread stuff I would only go with 1 wrap... my opinion. You don't want any of the teflon slivers getting into the system.

You will get some water probably but not alot. Have some towels handy or a bucket.
Have a thumb ready to cover the hole when you take the old one off, and have the new one in reach so you can screw it right back on. If you have any disposable diapers in the house they make great mops. If there is anything under this thing that can get wet and damaged, cover with plastic... particularly any electrical controls!

You don't have to use an EXACT replacement, Home Depot and Lowes may have the "No 67 Maid-O-Mist" which will work just fine. Make sure you purchase the model with the correct size threads! (Typically 1/8" NPT)

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: