An efficient way to detect leaks is to fill the tubes with a tracer gas at the service pressure to analyze the air around the conection with a detector adapted to this gas. The reversse may also be done, putting the connection in a tight box filled with a tracer gas and analyze the gaz in the tube.

Possible tracer gases and detectors are

light hydrocarbons (methane ethane, etc.) and flame ionisation detector

halogenated gases with electron capture detector

CO2 or water vapour and infrared detectors

An obvious method to detect important leakages may also be usefull: fill the tube with air under pressure and put the connection under water. Bubles will appear at importantn leakages.

An efficient way to detect leaks is to fill the tubes with a tracer gas at the service pressure to analyze the air around the conection with a detector adapted to this gas. The reversse may also be done, putting the connection in a tight box filled with a tracer gas and analyze the gaz in the tube.

Possible tracer gases and detectors are

light hydrocarbons (methane ethane, etc.) and flame ionisation detector

halogenated gases with electron capture detector

CO2 or water vapour and infrared detectors

An obvious method to detect important leakages may also be usefull: fill the tube with air under pressure and put the connection under water. Bubles will appear at importantn leakages.

hydrogen testing or pressure drop test, so you can apply a constant pressure in the tube and mesure if the there is any pressure drop.

http://www.nordenmachinery.com/en/home/innovation/Leak_Testing

I agree with Claude 's answer

Also these links may help you

http://www.charlottepipe.com/Documents/PL_Tech_Man/Charlotte_Plastics_Tech_Manual.pdf

https://plasticpipe.org/pdf/chapter09.pdf

http://www.simona.de/fileadmin/user_upload/Medien/Mediacenter/Verarbeitungshinweise/work.info_-_Gluing.pdf