This is gonna sound like it's off topic, but it's not, so please bear with me...
I bought a commercial water level sensor not long ago. It was one of those type that you drop a hard plastic tube in the tank, and the hard tube is connected to silicon airtubing, which is connected to a pressure sensor. When the water goes up or down, the air in the tube is compressed or expanded - changing the air pressure in the airline tubing, which is sensed by the pressure sensor, which turns things (like a fill pump) on or off.
I was taking real detailed measurements, and day in, and day out, the tank had to be filled higher and higher for the senor to register it as "full". So I orderd some of Rex's CO2 tubing, and replaced the 8' of silicone airline with his tubing. The change in day to day readings changed RADICALLY. The rise in the sensor's percieved "full" level got MUCH more consistent. Why?
My personal conclusion is that the vendor supplied 8' section of silicone tubing leaked a wee bit of air every day, so it took an increasingly high water level to set of the sensor. With Rex's leak free tubing replacing it, that leaking stopped, and the senor became, immediately, MUCH more accurate.
My conclusion - silicone airline tubing has slow leaks under even low pressures, and Rex's stuff does not.
It ain't airtight proof. But it is a solid piece of evidence.