Marine color doser not staying primed

[jap783]

I have an Amazon marine color doser that keeps losing its prime on channels 1 and 3 after an hour. I changed the head on both and replaced the motor on 1 just in case. it doesn’t seem to have a leak anywhere. Has anyone encountered this problem before?

 

[laverda]

There is only two possible causes.
1. the rollers are not sealing the tubing off. This happens as the tubing gets stretched thinner over time.
2. Air leaks at the connections or in the hose. It looks like you have 10 connections on each dosing head. I would try to simplify that if possible. Leaks on the output side will not cause your problem. So look closely at the side drawing fluids in. Noting will leak out as it is under negative pressure. Air is being drawn in.
What are the extra parts you have in your lines? One looks like a quick disconnect connector, but I can tell what the others are on my phone. I would eliminate everything but the one connector.

 

[jap783]

The extra parts are for converting the head tubing to RO tubing for ease of plumbing. Unfortunately I could not find any single part that would convert 1/16" ID tubing to 1/4" RO tubing and needed three parts to do the process. To ensure that it wasn't staying primed I placed an empty graduated cylinder at the intake of the line and it filled up in 2 days. Come to find out, it was the roller heads themselves and I must not have changed them. Are there any recommendations for suppliers that have RO tubing to doses tubing?

 

[Darren in Tacoma]

Something like this, in the correct size will allow you to go from product tubing straight to squeeze tube. Also, the squeeze tube will be pliable enough to stretch over a slightly oversized barb and a couple of zip ties will keep it all together.