On 15 Aug 2018 11:28:15 GMT, dpb wrote:

You really don't seem to observe very much for all the looking you
describe...

I agree with you.
It's obvious to all that how the system works was a mystery to me.
And, it's just as obvious that it's only slowing dawning on me what all the
pieces are and what they do (and where they should be).

The nut is welded onto the tank to screw in a hook eye to move it with...
Ah. I see. It would make sense.
Thanks for that input as to what that top nut was for.

And you should recharge it (when it is as empty as you can possibly get
it) to -2 psi from the pressure switch cutoff pressure. Leaving it so
low cam lead to premature failure of the diaphragm from over-flexing.

I'm confused by that advice - which isn't to say it's wrong - I just don't
know yet what the "cutoff pressure" is set to.

I can see that the water storage tanks alone seem to be supplying about 55
psi according to the gauge at the front of the booster pump, if that
reading is correct.

One anomaly I just realized exists is that when the bladder read 18 psi,
the gauge at the pump read around 55 to 60 psi, which shouldn't be, right?

Shouldn't both the bladder and pump gauge read the same pressure?

NOTE: Since I have a 220VAC compressor on wheels, I can remove its gauge
and swap it with the gauge on the booster pump motor to ensure that the
readings on the gauge are accurate.

That's suggestive that the overall system is still actually operating at
the nominal 60-40 setpoint range, not something approaching 70-75 psi.

I agree that, yesterday, it was higher than today, with the only difference
that could be appreciable being that the temperature in the morning is a
good 20 degrees cooler than in the later afternoon.

I can check the gauge pressure later today - where I think I should just
replace that gauge on the booster pump to ensure that it's reading
correctly, since the bladder read 18psi clearly (multiple tests) while the
booster pump gauge read 55 psi at the same time.

I don't trust that old gauge much; you need to get a wider range gauge
to read the pressure in the pressure tank accurately in order to know
where your pressure switch setpoint is and to precharge it correctly for
the operating pressure.

I agree on both counts that I need a better gauge (my tire gauge stops at
60psi which is about 10 or 20 psi too low).

I have a 220VAC air compressor and lots of fittings so I can dig up another
gauge I think. Replacing the old gauge on the pump motor will go a long way
toward allowing us to trust the readings.

I'd take the other gauge out to check it actually does zero...where the
50+ psi came from with the pressure tank empty and showing 20 and only
5 psi or so from the external tank head is a mystery (unless the well
pump was on?).

I didn't think about the well pump - good catch - it could have been on as
I didn't shut its breaker off. I should have.

But I agree inherently with you that I need to replace that old pump gauge
just so I can be sure to trust it. I'll work on that today if I can dig up
a gauge; otherwise, I'll buy one.