I have a fill-o-meter, when I fill 1-2 litres into a bucket it's spot on. When I fill my HLT with 60l either through the ball valve or right over the top, it's 20l out.
I know the markings on my HLT are correct as I weighed each litre of water and also my brews always come out spot on.
Any ideas Kegland?
This seems quite strange. The Fill O Meter should be far more accurate than this and certainly we have got much better results than this in our testing. We do have means of calibration but I don't think this is the issue. I would check your flow rate first. If you have your water running too fast you could have an issue that the flow sensor cannot read that fast. The flow sensor we use has a flow speed range of 1-30L/min so my first guess is that you might be exceeding the 30l/min.
Other areas of error are hose expansion or hose volume. For instance if you have a very long hose you will have some elasticity in the hose that will hold 1-2 litres of water when under pressure. For instance if you have a valve at the end of the hose then the hose is already pressurised then the pressurised hose may dispense as much as 1-2 litres. In addition to this if you have a hose that contains a volume that will drain out this can also give you some error. For instance once the solenoid valve turns off and if you have liquid in the hose that can slowly drain out this can cause some error. With that said these errors caused by the hose are way less than the 20L issue you have so I really think you are probably exceeding the flow speed of the sensor.