That would certainly affect the SeeLevel readings, but I would still install it anyway.
When I added a gallon at a time to our gray tank and recorded the SeeLevel readings, I created a spreadsheet of the results. I printed out the results and taped it to the wall above the display. At a glance, I can tell that what the actual level is for each reading of the displayed values.
The system displays in increments of three or four percent.
