Letting air out of system. Other observations

Ross11988

hi all. I have a hot water boiler that propane fed. The upstairs pipes have been making banging sounds when the furnace kicks on. I looked and saw people recommended purging air out of the system. Found a video on YouTube on the basics. Shut off furnace, let water cool. Turned off ball valves, set actuators to manual, hooked up hose to outlet and opened gate valve. Most of the pipes had no water in them except for 1. Should that be normal? I’m still hearing banging on top floor

Other things I noticed.
Taco air valve is missing top

Pressure gauge shows 0 psi

pictures attached.

much appreciated!

EdTheHeaterMan

Interesting comment

Lots of detail

Ross11988

https://forum.heatinghelp.com/discussion/comment/1840134#Comment_1840134

sorry. Just added all the details

Ross11988

Just noticed this. Leaking from this air valve coming out of furnace?

EdTheHeaterMan

OK somewhere is a valve that feeds water to the system. It appears to be connected to the expansion tank. you have an interesting expansion tank called a Fill-trol® The concept is that there is 12 PSI air pressure in the tank and that pressure inflates the membrane that separates the air from the water in that tank. At the top of the tank membrane there is a metal actuator that pushed the fill valve open to let water into the boiler closed system. once the boiler pressure gets to 12 PSI the water pressure starts to push back on the membrane in the tank. When the boiler pressure gets just slightly above 12 PSI the membrane's valve actuator will get pushed away from the valve and the water will stop feeding.

There is something wrong with that tank or that valve because your boiler pressure is at zero. That is not good.

More to follow.

DCContrarian

Losing water is not normal. A hot water system should hold it's water forever. Once you get it filled and the air out you have to figure out where the water is going.

EdTheHeaterMan

Here is the regular Extrol expansion tank.

You ca nsee the steel tank from the outside. Inside there is a flexible (black) membrane that separates the Water side from the Air side of that tank. that way the tank can be pre-charged at the factory with 12 PSI Air pressure. There is a Schrader Valve (like on a tire) on the bottom of the tank where you can check the pressure in the tank with a tire pressure gauge, and add more air as needed to keep the system operational.

Your expansion tank has a special feature that operates the fill valve.

In the cut away illustration you can see the membrane (in red) and the metal valve actuator (in gray) attached to the top of the membrane. I believe that one of 2 things are wrong with your tank.

1. The membrane has failed and let all the air leak into the radiators
2. The valve is clogged and will not let any water into the system.

To determine what the problem is, ther is a simple test. Take the cap off the schrader valve and try to let some air out of the tank. if you get water, then you need a new tank because the membrane has failed and is leaking water past the membrane. If you don't get any water, that is a good thing. Now you wantto check the air pressure while the boiler gauge is at zero PSI. If you don't get any air pressure or the pressure is lower than 12 PSI, you will need to get a bicycle pump and add pressure to the air side of the tank. You will want to close the manual water feed valve (blue handle) so you do not add any water as you pump up the air in the tank.

Once you get to 12 PSI air pressure in the tank, then you can open the boiler feed valve (blue handle) and see if the water fills the boiler to 12 PSI on the boiler gauge.

Let me know what you find up to this point.

hot_rod

Looks like the air purger is on the return piping to the boiler? The air vent in the boiler is probably doing the most work. I'd replace that one for sure.

There are a number of upgrades you could make to get an efficient, quiet system. If you wanted to do some repiping?

Screenshot 2025-02-04 at 12.24.19 PM.png

Ross11988

https://forum.heatinghelp.com/discussion/comment/1840165#Comment_1840165

thanks Ed,

I poked the bottom valve with a screw driver and just got water. No air.

EBEBRATT-Ed

Your expansion tank is bad and needs to be replaced.

EdTheHeaterMan

Don't get the wrong one.

https://www.supplyhouse.com/Amtrol-110-1-Model-110-Fill-Trol-w-Valve-44-Gallon-Volume-4910000-p?_br_psugg_q=filtrol

be sure to get the Fill-Trol® tank. the Extrol tank will not fit. You may need to get it with the new valve if they don't have the 110 tank only in stock. Look at your tank model number you may have a smaller 109 tank only. No need to get the 110 if the 109 will work.

While you are at it, get 2 new Air vents

Ross11988

https://forum.heatinghelp.com/discussion/comment/1840198#Comment_1840198

thanks so much Ed! Yes once I spun it around that’s the same model I have. I assume the two vents that should be replaced are the one on top of the expansion tank and the one that’s leaking on the furnace?

Much appreciated!

Ross11988

all quick update. Hooked up the new expansion tank and air vents and pressure came right back to around 12psi. Then actually heard water going through the pipes and baseboards. Don’t recall hearing that before. Appreciate all the help, especially EdTheHeaterMan!

delcrossv

Now you can purge the air out of the system.