Replace maid o mist, or keep cap tightened?

bubbajoe

I watched some youtube videos on bleeding air from a heating system. A couple of them discussed various parts of the overall system. They showed an automatic air release valve above the expansion tank and pointed out that it is "CRITICAL" that the little cap be loose.

Now...I have no plumbing experience at all so I decided not to try to drain the system to get all the air out. But I did notice our system has a 'maid o mist' automatic vent on top of the 'american air purger' air scoop, which is above the expansion tank. I checked the cap, and it was not loose. I loosened it and got a few little hisses of air, then water streamed out slowly. So, I tightened it back up.

'Researching' the issue brought me here. I've seen many posts on here that suggest all these type of vents will eventually leak, so just tighten the cap.

So, I have two questions:
Should I replace the maid o mist, or just leave the cap tight?
Could this cap being tight, have led to our problem of having gurgling sounds coming from the baseboard registers?

Jamie Hall

Oh boy. I presume that your system heats the house with hot water pumped around to various baseboards? Then it is what is called a hot water system.

A few basics. A hot water system has a boiler and, almost always, a pump or pumps to circulate the water through the house. Since water expands when it is heated, it will also have an expansion tank. That expansion tank needs to have some air in it, but how it gets there and stays there is variable.

So... first thing would be a couple of pictures of the expansion tank and the piping and controls in the vicinity of the boiler.

Now on gurgling and getting air out. The system is intended to be full of water all the time. To get the initial air out, you don't drain the system -- that would just add air! -- rather you purge it, which means running water through it at fairly high velocity to push all the air along and out. Then to keep the air out, two things: the pressure in the system has to be high enough, and you need an air removal gadget -- of which there are many.

So the next thing would be a photo or two of your air scoop or whatever and the air release on top of it, and any pressure gauges you have on the system.

bubbajoe

When I said drain, I meant bleed or purge. I understand it's a water system. I had decided not to take on the project myself.

This is the air scoop/maid o mist vent on top of the expansion tank.


These are the rest of system



The pressure guage on the boiler reads from 20 to 22 psi. The only place I see to attach a hose is just below the valve controllers, but that's the supply side? The tank sounds fine, solid on top, hollow at the bottom.

Anyway, my initial post was to ask if the maid o mist should be replaced, or just leave the cap tight? Just a couple months ago, a "seasonal inspection" was done on this system. I'm assuming the tech is the one that tightened the cap. There does not seem to be any bleed valves up on the baseboard heaters themselves.

Could this cap being tight, have led to our problem of having gurgling sounds coming from the baseboard registers?

Jamie Hall

In answer to the direct question, yes. That air eliminator is there … to eliminate air. And if the cap is screwed down tight, it can't do that.

bubbajoe

Thank you for your rep!y

bubbajoe

Now that I have posted pictures of the system, woild anyone like to guide me toward the proper process of purging the air out of the system?

mattmia2

If you replace the automatic air vent with one that doesn't leak it should work its way out through the automatic air vent on its own. If the automatic vent was leaking water, the water the automatic valve added to replace it would have contained dissolved air that would have gotten in to the system.

neilc

then we need to discuss that the circ is pumping towards the expansion tank,
this will also make for a noisy system.

EdTheHeaterMan

Here are your instructions for purging air fro your system.

Turn of the electric switch to the oil burner



Look for the manual open lever on the zone valves. Place them in manual-open mode.
Locate the pressure gauge and monitor the pressure during this procedure if the pressure gets near 28 PSI you will need to close with the label “Water Shut Off” until the pressure drops or the relief valve will release the boiler pressure when it goes above 30 PSI.
Now close valves number 1,2,3 & 4
Put a garden hose on to the boiler drain valve # 5 and run the other end to a drain or outside
Make sure water Water Shut Off (WSO) is open full
Now open valve # 2
Raise the auto-feed manual handle up to the fully open position and be ready to quickly open the boiler drain valve #5 when the boiler pressure reaches 28 PSI You want a lot of water pressure to force any air in the pipes down to the boiler drain and garden hose in the boiler room.
As the pressure drops below 10 PSI you will want to close the boiler drain number 5 to build up pressure then open valve #5 when the pressure reaches 28 PSI. You may need to do this 3 or 4 times on the long zone loops or the second-floor loops to purge all the air.
Once you are confident that no more air is in the loop served by valve # 2 you will want to close valve # 2 and open valve # 3 simultaneously. Repeat steps 8 & 9 until you are confident there is no more air in the loop served by valve 3
Once you are confident there is no more air in 3 then you will want to close valve # 3 and open valve # 4 simultaneously.
Once you are confident there is no more air in #4 then set the manual handle on the auto-feed valve back to automatic position. And promptly close the boiler drain # 5 once the pressure is down to 12 to 15 PSI.
Place the zone valve manual-open levers back to automatic position. Place valve # 1, 2 & 3 to fully open and be sure valve 4 is fully open. Valve # 5 should be fully closed. WSO valve can be returned to the position you originally found. (open or closed) Many on this site will recommend fully closed but I think you may want to leave it open for a few days to allow for any dissolved air in the new water you just added to separate and find its way to the air scoop. If you don’t replace the Maid-O-mist vent then you will need to open the cap several times over the next few days to let out any air collected in the air scoop.
After a few days, you can close the WSO valve and leave the cap tight on the air vent.

bubbajoe

Ok, wow...thanks so much for all your replies. I think I may give it a try. But, edtheheaterman-I am not sure what you mean by valve #5. Do you mean the one below and to the left of the zone valves? (Which you labeled #4) This is the only place to attach a hose to. Also, you labeled two valves as #3. I assume those are 3 +4?

As far as the circ pumping toward the expansion tank, perhaps the picfure just makes it look like that? Two pipes come out of the boiler one goes to expansion tank, then the zone valves. The other goes to taco cartridge ciculator.

EdTheHeaterMan

oops posted wrong pic

EdTheHeaterMan

bubbajoe said:

Ok, wow...thanks so much for all your replies. I think I may give it a try. But, edtheheaterman-I am not sure what you mean by valve #5. Do you mean the one below and to the left of the zone valves? (Which you labeled #4) This is the only place to attach a hose to. Also, you labeled two valves as #3. I assume those are 3 +4?

As far as the circ pumping toward the expansion tank, perhaps the picfure just makes it look like that? Two pipes come out of the boiler one goes to expansion tank, then the zone valves. The other goes to taco cartridge ciculator.

you got it right. I corrected the picture

neilc

bubbajoe said:

As far as the circ pumping toward the expansion tank, perhaps the picfure just makes it look like that? Two pipes come out of the boiler one goes to expansion tank, then the zone valves. The other goes to taco cartridge ciculator.

I see the circ pumping into the bottom of the boiler,
then the other boiler supply pipe leaving towards the tank,
that is what is meant as pumping towards the tank, which is wrong.
Circ should pump away from the tank.
Ideally you would move the tank and water feed to before the Circ.