Pressure loss in radiant system

scrantch

Is it normal to lose pressure when system is off? It reads about 10 lbs cold and when the the heat is on it goes to about 28lbs. It used to stay more constant, like 18 lbs when originally set up.

Dave T_2

classic symptoms of defective expansion tank.

scrantch

Thank God I thought there may have been a leak in the pex in the slab

hot_rod

if only that green handled ball valve would have been below the tee That would make for a quick and easy tank removal check or replacement.

scrantch

I know another plumber said the guy must have been stoned when he set up this system.

scrantch

What do I do, stick my finger in it while I screw the new tank on with one hand? Antifreeze dripping everywhere.

hot_rod

scrantch said:

What do I do, stick my finger in it while I screw the new tank on with one hand? Antifreeze dripping everywhere.

Yeah, it's never pretty changing out or removing a tank, especially if it is waterlogged.
I slip a 5 gallon bucket over the tank, lossen the thread and let it dribble into the bucket.
It will be heavy!

I'd remove the tank and have an iso valve all doped up and ready to go. That will be easier to screw in, compared to a tank. Now you have a quick connection, and an iso valve for the next guy.

Dave T_2

@hot_rod nailed it. Shut off the feeder and be sure to attempt this after the boiler has cooled off to a temperature that cannot harm you (colder the better). IF diy do it 1st am on middle of the week in case you need to call in help. If you shut off feeder (green handle valve above tank) and turn off boiler, most of the pressure will drop as it cools off.
Remember - any water that is lost (including most of the waterlogged tank) will need to be replaced and this is going to dilute your antifreeze solution.
A prepared, experienced tech can pull this replacement off (sounds like @hot_rod has done it more than once) BUT I can think of many things that can wrong, good luck!

HomerJSmith

Dave T_2, is correct. If you lose your air charge on the expansion tank, the E-Tank fills with boiler water and when the boiler heats up the expanding water has no where to go because it is already filled with water and not air and the pressure rises.

The tank looks new. How old is it? If it is an Extrol, the last two digits on the serial number is the year and the preceding two digits are the week.

I would set the air charge to 15 psi. If you remove the blue cap on the bottom of the tank and depress the valve and water squirts out, you may need a new tank. This tire valve is where you would add air to the air side of the bladder.

To go from 10 psi, cold, to 28 psi, hot, means your tank isn't regulating.

HomerJSmith

On another post I did give an idea of how to air charge the tank without disconnection it from the sys.

MikeL_2

While performing these changeouts, we cover nearby electric components, burner, gas valves, etc. with plastic to prevent accidental drownings.