I've switched the configuration for now to only fill my water barrell and just feed the float valves off that; will see if this makes a difference. It usually takes about overnight to fill that thing and it holds, I think, 40g, so a fill should last me about a week.
If I flush the membrane then the TDS on the output falls down to 15 which to me seems a more acceptable level (although I still wish it were a little better, but hey it's better than 60).
As far as configuration goes I'm not really sure how you can screw up with these things? Water goes in, water comes out in two places, and one of those streams is more better than the other.
You need a flow restrictor that matches your membrane capacity and you put that on the waste line (otherwise a flush kit doesn't do anything). Am I overlooking anything here? And then I guess the only thing is if you want to get real tricky you can put a flush bypass valve on your waste line, and the solenoid shutoff which feeds off the output line and impacts back to the input line.
I guess when I say "three membranes" I should qualify that the first was, of course, several years old so maybe it doesn't count. So really I'm looking at being on my second replacement membrane and I'm wondering what's up. I would have upgraded the membrane anyhow though since the old one was 35gpd and I wanted to go to 100gpd (although it's not 100gpd at the pressure it's run on). I am using, as far as I know, the appropriate sized flow restrictor.
Anyhow thanks for the thoughts ... will have to scratch the noggin a bit more on this but for now I'll see if the reservoir changeout has an effect.