Apex DOS New Pump Heads Still Losing Prime

[QuinnLee512]

Bought a used DOS from R2R. It keeps on losing prime even though I have replaced the pump heads. I am using this silicone tubing and it fits pretty snug. I'm debating if I should try converting to John Quest fittings? Pretty disappointed. Never had this issue with my cheap Kamoer X-1 pump.

Amazon product ASIN B07PPSVJZC

 

[QuinnLee512]

Not sure why Amazon link won't display but this is the description for the tubing.

uxcell Silicone Tubing 5/32"(4mm) ID x 1/4"(6mm) OD 16ft 5m Flexible Silicone Rubber Tube Air Hose Water Pipe for Pump Transfer Clear​

 

[SuncrestReef]

I had really bad results with air leaks every time I used silicone tubing, both with the stock DOS fittings and with John Guest push-connect fittings. When I switched back to the standard Neptune tubing or 1/4" RO/Di tubing, it worked perfectly with either fitting. Read my DOS Tutorial for tips on creating a tight seal for the tubing:

https://www.reef2reef.com/ams/neptune-apex-tutorials-part-9-dos.849/

 

[QuinnLee512]

Thank you. I never liked how stiff the provided tubing was. I just ordered new ones and will give it another try.