air in lines increases with pressure?

[PaulLovesJamie]

I'm hoping somebody can explain something I observed today.
I'm getting air in the line for one of my bays, concurrent with some pulsation and apparent reduced pressure felt at the bay/gun. (I say apparent because the gauges say pressure is ok.)
Now, I mostly know what to do to fix "air in the lines", but heres what I noticed that is interesting.
With the bay running, trigger NOT pulled (because I was in the ER), I loosened up the unloader to reduce pressure to a couple hundred lbs. Then as I was cranking it back up I notice that the amount of air increased. Rapidly, and a lot. I have clear polybraid hoses on the bypass for the unloader, plumbed back into the pump inlet. Thats where I can see the air bubbles - a lot, and very large. Enough that I thought $@#! how did I not see that before.

So I know that as I crank up the pressure more water is bypassing. What I saw was not water moving faster, I saw it go from a few % small bubbles to maybe 20-30% of the volume was air, huge bubbles.

I *think* I know whats going on, but...
Thoughts? Opinions?

 

[Waxman]

Maybe the city flushed or repaired some waterlines getting some air into the city water system?

 

[PaulLovesJamie]

Waxman, thanks, its only 1 bay though so unlikely.

 

[PaulLovesJamie]

I was hoping for a confirmation or other ideas, oh well.
I suspect that the low pressure seal was bad, and at higher pressure with lots of water bypassing it was sucking air in thru the seals, at a seemingly increasing rate as the pressure increased. So my thought was that this might be a diagnostic indicator - if I have a pulsation/cavitation issue, perhaps watching for an air increase in the bypass hose while adjusting the pressure would confirm that I have a bad seal, helping avoid inspecting fittings etc.

I did install a seal kit, and all pressure/pulsation/air problems are gone. So I think that confirms that the seals were bad, and *maybe* confirms that I can use the pressure-adjustment-air test to confirm a bad seal diagnosis. Time will tell. Or, maybe you guys can tell me