ultrasonic distance sensor

Yes, easy as can be, just make sure that the tube is perfectly straight and the distance is NOT any multiply of 1/4 wave length. In such conditions you get an ultrasonic musical instrument vibrating to your tune;^).

Happy music, have fun.

Stanislaw.

I would sure think so -- but the reading will be a bit different than expected because sound travels more slowly in a tube than it does in free space.

Your round-trip travel time for 150 ft will be almost 300 mS so you'll surely have to modify the rangefinder elex or build your own. Putting the transducer down the pipe a ways would eliminate that issue, just have it a couple of feet above highest expected water level.

National used to make a little sonar chip, LM1812. It's long obsolete but it might work nicely if you can find one.

Ultrasonic transducers are easy to find surplus. See, e.g.,

You can use the same 'ducer for xmit and receive, just as fishing sonars do.