We also have a Tank Tender, but the 10 tank model. We only use 6 of them.
When we bought our boat, only one or two tanks would read properly. Some read zero, some read full scale, and the rest leaked so badly you could not tell what the reading was. All of this was caused by broken, blocked, or leaking tubes.
I replaced all tubing on the boat. Two tanks still would not read properly and I found the vertical stiff tubing that is inside the tank was broken. I replaced all of these and it solved
A few months later, one tank stopped reading properly. I traced it to a kink in the tube where I did a poor job during the install. Rather than rerun it, I cut it and repaired with a double compression
fitting. I have had no further problems.
I bought several fittings and olives for my tool box before leaving the US in case I have any more issues.
One suggestion that I could offer - to allow for future repairs
, when you are running your new tubing put in a coil of extra tubing somewhere along the line. One loop will give you a foot or so of slack that you may someday need to allow you to repair a broken tube. In my case, I had a little out of the way spot after the tube had been snaked from the nav station and behind the freezer
to the area under the sole. This was where I coiled up my extra loops of the tubing and ty-rapped them neatly together. Saved me from re-running the entire line and allowed me to put in a double compression