air bubbles in dosing line doser 2.1

I've bought a slave doser 2.1 with my SA + KHD unit.

I calibrated the pumps. But the first days my dosing lines seems to run empty into the sump.
So i placed check valves in the suction and pressure side of the doser.
Suction side is no problem, but in the outlet lines to the sump, big airpockets keep turning up.
I use the original GHL silicon tube, lines are about 1.7 meters long.
Tubing is pushed all the way up on the connection pieces.

With the airpockets in the lines, i can't dose precise amounts.
Should i place the checkvalve at the end of the dosing line or are there other solutions.
I never had this problem with my h2ocean P4 pro dosing pumps.
I would like to change everything to GHL if i get this sorted out.

Attachment 13200

Attachment 13201

Attachment 13202

The tube connections look OK.

Do you know the age of the dosing pump?
Do you know when the original owner replaced the tubes or if it was done at all?

You can manually run a dose for 40 - 50ml and as the pumps are running, pinch the areas where air accumulates. This will flush it out. Afterwards, run 2-3 manual doses for a few ml and see if the bubbles develop immediately or not. If no bubbles develop immediately, the air may be caused by the gas exchange from the liquid being dosed. In that case, it would be worth trying a tube of a different material such as flex PVC (same kind of tubing used by the KHD reagent pump).

Vinny,

The slave doser is completely new, 3 weeks old. As is my KHD with SA unit, brandnew.
I'm not impressed by either at this point. KHD is in an other topic.
But i know most people are ok with it, so i pressume it will work out fine, once i figure out what i'm doing wrong.

I was in the proces of changing my gear to new GHL equipement. was looking for another new slave doser, but for now i will keep my last DD H2ocean P4 pro running. No bubbles, airpockets, no check valves needed.
The new profilux 4e starterset also has to wait, till hopefully the doser and KHD are running trustworthy.


I think the problem is that the GHL silicone tubing is not thight enough on the connection piece, suction side of the doser pump.
If i use a tie wrap to thighten the connection it even get worse. I think the tie wrap is to big and is not good connected on the wider piece of the connection piece. With the tie wrap on the suction side, the pressure side of the pump is producing a lot of air bubbles. If i remove the tie wrap, it is much better.
So i will change all my GHL silicone tubing to flex PVC.

The air bubbles problem didn't occur with my DD h2ocean P4 pro dosing pumps. Containers and liquids are the same. I just replaced the DD dosing pump with a GHL 2.1 slave doser and the original GHL silicone tubing.

flex tube is ordered, probably delivery tomorow.
Is it necessary to install check valves whith de doser 2.1?
Maybe i can first try to change the silicone tube with flex tube without check valves?

checkvalves are not needed with my running DD h2ocean P4 pro.

Check valves are unnecessary.

2 days ago, i changed the GHL silicone tube for GHL flex PVC.
Problems solved, no airpockets or bubbles. No checkvalves needed, just as a good dosing pump should do.

As thought the problem is that the siliconetube is not tight enough on the connection piece (suction side) of the dosing pump. When the pump starts it draws a little bit air inside.
I don't understand that GHL promote silicone tube as standard.