Yikes...lost my water pressure/heat to slab...air in the lines?

[Scotty2]

The questions:
Do I need to re-pressurize the expansion tank to clear out the air?
Should I close all lines in the slab and run one at a time to clear the air?
The back story:
I noticed that the small blue (expansion?) tank read 0 psi...so I hooked up a hose and turned on the water to re-pressurize. The pressure gauge didn't move right away so I went to check on the pump at the Spring and determined I had a leak in the line that I was hooked up to, thus no water pressure.
Came back later to find that I somehow added air to the lines...now no heat to the slab.
Tank is 185...far side of the HE is 178 going to and from the Primary loop (where the expansion tank is).
Far side of the primary loop it's 65 going into the 3 way Mixing valve, 58 to the slab and 65 coming from the slab to the primary and MV.
Pumps all working
I can see air bubbles in the sight vials on each run of pex in the warehouse.

 

[maple1]

The only way you will lose pressure, is if you have a leak of some kind.

You will need to post more details, and maybe some pics of what you have, maybe also a diagram?

How old is this tank? What kind of tank is it? Where exactly is this pressure gauge in your system? And tank? Do you have more than one pressure gauge?

It could be possible that the air cushion somehow got out of your tank, and escaped through a vent. If its a bladder tank, the bladder may have let go & you might need a new tank. Is it a bladder tank? Is there still air pressure in it on the dry side? Just spuriously (is that a word?) adding more water in is not a fix, it would just replace the air cushion - which you need. So before you go to trying to bleed air out, or add water, you need to verify what the problem is/was. Multiple pressure gauges around the system are highly recommended. Could also be possible you have a leak in your slab...

 

[Scotty2]

My recollection is that everything is new this year, except some of the pumps.
It was running fine (although the pressure gauge read zero psi), until I hooked up a low pressure garden hose, thinking I going to re-pressurize with the pressure of the hose water...thus, I'm thinking it's too coincidental to be anything but that.
I believe the pressure gauge has hovered around 25 psi, sometimes lower, sometimes higher...I figure it was still purging some air in the system as it's only be running 6 weeks or so.

 

[Scotty2]

Yay! Got it working. Hooked up a garden hose to an outdoor hose bib that for some reason gets the highest pressure of anywhere on the farm, with the other end hooked up near the Mixing Valve.
Got rid of the air lock almost immediately.
Left it hooked up for an hour or so until the pressure was up to 50psi.
I'll see how long it takes for it to creep back to zero.

 

[maple1]

50 is way too much. Should only be 15-20.

You said once it was zero then said around 25? Hard to follow....

 

[Scotty2]

50 is way too much. Should only be 15-20.

You said once it was zero then said around 25? Hard to follow....

I put the psi up to 50 as I'm assuming there is a lot of air to purge in the system, which would drop the psi eventually.
What's the downside to running a high psi?

 

[Fred61]

I put the psi up to 50 as I'm assuming there is a lot of air to purge in the system, which would drop the psi eventually.

What's the downside to running a high psi?

T P valve blowing? That will also lower the pressure.