I've looked at those tools. Decided they weren't necessary.
Scum layer is easy to measure just by carefully scooping it out.
Sludge layer is also easy to measure, it's the difference between
the depth to bottom, measured with any narrow rod/pipe, and
the distance to top of sludge, measured with any pipe etc with
a "foot" attached to it. If the foot is even a half a square foot
you'll easily fell the sludge and not penetrate it more than slightly.
BTW, I'm big believer in measuring sludge and scum and having
tank(s) pumped when they need it, not on a schedule.
If it's newer tank it'll also have an outflow filter. Clean that while
you're there.
EDIT: Here's a good resource:
https://inspectapedia.com/septic/Septic_Tank_Sewage_Levels.php
Scum layer is easy to measure just by carefully scooping it out.
Sludge layer is also easy to measure, it's the difference between
the depth to bottom, measured with any narrow rod/pipe, and
the distance to top of sludge, measured with any pipe etc with
a "foot" attached to it. If the foot is even a half a square foot
you'll easily fell the sludge and not penetrate it more than slightly.
BTW, I'm big believer in measuring sludge and scum and having
tank(s) pumped when they need it, not on a schedule.
If it's newer tank it'll also have an outflow filter. Clean that while
you're there.
EDIT: Here's a good resource:
https://inspectapedia.com/septic/Septic_Tank_Sewage_Levels.php
