There appears to be a problem with the liquidators re white scaling forming in the tubes.... Borates in the pool tend to help with this problem,...
Yes, reading through some threads on the forum it appears that some people have had this problem and in some cases borates seem to help, but it does not seems to be a general problem with the Liquidator. I used a Liquidator all last season without any scaling problems.
I've also read that the flow metres are pretty crappy, ...
Not sure why this is even relevant. It just provides relative indicator of flow. Once you've dialed in the correct flow to achieve the FC the only value that the flowmeter adds is that you can tell if the flow has changed. But you already know this since your measuring FC on a regular bases. I actually contemplating taking my out of the system this year.
... and they can also drain the entire contents of the liquidator into your pool due to suction problems....
Well, given the design of the liquidator, with the input and output float values mounted at the top of the container, I don't see how this is even possible.
After my first year of using the Liquidator, here what I see as problems or inconveniences:
1) As pump pressure goes up and therefore you suction, the flow rate from the Liquidator decreases, lowering the amount of chlorine injected into the pool. But again since your suppose to be measureing FC on a regular bases, you will notice this and make the appropriate adjustments
2) The ball valve provided with the Liquidator to adjust flow rates is inadequate to make the fine adjustments. It can be done, but needle valve (pricey) would be much better.
3) Length of time that you can go without refilling with chlorine. It all depends on how big a pool you have, the normal daily FC demand and the strength of chlorine that you use. With my pool of ~30K gallons and using 12.5% chlorine, I was able to maintain 4 to 7 ppm FC for (cya ~60) for just over a week.