Air in the plumbing

We have a Rainsoft whole house filter system. It comprises of three tanks, one that is apparently the main filter tank, another that is mostly water with air at the top to provide some pressure and air in the water and finally a third for water softening (gold series).

We're new to these types of systems having moved from a city house out into the country, so we're learning as we go.

I think I've now figured out most of the system and we've had Rainsoft check out the system last year, all was apparently fine with it.

In the last few months we've been getting a LOT of air in the plumbing. My wife called our Rainsoft dealer who was very nice and suggested it could be the manual valve on the top of the second pump that is connected to a matrix of clear hoses used to flush out water during back flush. We'd been fiddling with this valve not knowing if it should be shut or open, the Rainsoft service manager suggested it should be neither but somewhere between.

We put the valve about halfway open/closed and have been away for a week on holiday. During that time the system has done a couple of back-flush cycles which he'd suggested it would need to do to clear some of the air out.

So things are definitely better, but occasionally we still get air in the water, but here's my question. That second tank that is supposed to be mostly water with some air at the top, sounds likes it's completely full of air when I tap it on the side. I remember when the service rep came out and he explained what it was that when you tapped it you could hear it was a dull thud up until the top third (at least from memory).

I thought the system would regulate itself and this tank would eventually re-fill but it doesn't appear to be doing so and I'm guessing this is an issue.

So, how do I bleed some of the air from this tank? It has two outlets at the top, one goes to a little electric pump which comes on when we run water, the other goes through the previously mentioned valve, then through a blue electronic valve connected to a pump control circuit, then out to the clear waste pipes. Alternatively, SHOULD I try and bleed air, or should I be leaving it alone?

One other thing that happens occasionally, if we get a power cut the timer control on the top of the carbon filter (Silver series) will stop working even after power is restored. The clock is the first indication that it's stopped, the second is the sound of the ticking subtly changes tone (can you tell i've spent a lot of time looking at this thing!). It usually gets fixed if I unplug the power adapter for the unit, wait 10 seconds and then plug it in again. Somehow a power cut is tripping this unit up. I'm not sure if I need a new timer unit or a new power supply. Not this isn't digital unlike the Gold series unit. I'm also wondering if something else might have gone haywire also causing this air to come into the system.

We are also getting a lot of grey in our water occasionally. We were worried this was carbon from the filter, but the Rainsoft manager said it's sediment from the well getting through. What's odd is if I drain water from our blue water tank it's nice and clear so that seems odd to me. It also coincides with a renewed amount of air in the plumbing again.

So.. lot's of issues! We have Rainsoft coming out on October 8th, but I was hoping for some education prior to their visit to see if I can fix this.

Any advise appreciated.