Where’d you source the non contacts? I am definitely not in love with the opticals. They **** the bed pretty easy and MTBF is absolutely enormous. I’ve had some fail in a few weeks, others working fine for years. For example, I have 4 between two different RO storage vessels. On one of the storage containers, both sensors have failed at least once. On the other - been running fine for 4 years. The opticals in salt absolutely don’t last very long. The mechanicals are much more reliable.