@zboblamont I cut the pipe 200mm longer than the maximum height of the water, drill a 3mm breather
near the top cut a slant at the bottom of the pipe for the water to move freely, there is still a little fluctuation in the readings but overall way more stable when not bouncing off the wall of my water butt, also I have noticed at times when the sun shines on the pipe sticking out the top for about an hour in the morning the readings are more erratic. When I get a chance I will photo the setup and show the node-red flow that translates the distance into litres.

@Thomas-Weeks I have had great success with these sensors using a stillingwell (32mm plastic pipe with a breath hole and a 3d printed cap to position the sensor) a little experimentation and patience with positioning the sensor