I run 6 DOS units between 2 tanks, 2 for each tank for 3-part dosing + NoPoX and 1 for each tank for a six-weekly 24-hour AWC. I have had no issues with over/under filling, nor with any tubing disconnection issues. Dosing has also been very stable on both tanks.
For over/under filling you rely on the DOS calibration. I run a high and low level optical sensor in each tank’s sump. If it overfills the high level sensor would alert me. If it underfills then the Apex salinity probe would probably alert me first, due to the ATO replacing the missing SW, or if it ran the ATO dry, the low level sensor would go off.
With regard to tubing disconnections, I use the standard pressure fittings which I have had no issues with. Any time I set up or remove/refit (very infrequent) I carefully soak the tubing in boiled water to soften it before fitting and tightening. So far I have had no issues (5 years on one tank, 3 on the other and 3 for the AWC). Some others use a well known hack to retrofit push fittings in place of the standard pressure fittings as they don’t trust them. I haven’t done so yet.
I have only recalibrated each DOS once. I recalibrated the AWC DOSs after 18 months and they were still pretty much 100% accurate, think I adjusted one by a ml or two, nothing else. I recently recalibrated all 4 I use for dosing and a couple were out 3-4 ml. I am keeping an eye on the dosing container levels however as they still don’t appear perfect, so the recalibration may not have been quite correct. Next time I think I’ll run the recalibration process a few times to make sure I am getting a consistent reading before I make changes to the DOS.
Hope this helps, Brad.