Question: 

All in and running now, little bit concerned as the Clarisea is filling up due to the filter becoming blocked up, my return chamber is running low, the tunze then tops it up, then as the Filter roll runs around to a clean bit the water drains out back into my sump and then raises the level. Setting off the tunze alarm as the level is to high.

I think I know how to over come it.
Split off the float from the level sensor, when the Clarisea is just about to rotate the roll,set the level sensor at that level and set the float on the spare magnet that comes with it at my high level as normal.

When the filter roll turns the level will rise and cover the level sensor, but I can’t see that being a problem and as the water evaporates the sensor will pick it up and trigger the pump to fill again.

I don’t think it would be a problem on larger systems as the return chambers aren’t as small as mine and not so sensitive to fluctuations.

Just got to find my spare magnet and float holder to prove my theory.

Best Regards..
Answer: 

 

 
Just a bit of background - when first commissioned, the Clarisea SK3000 will take about 1750ml to “fill” (SK5000 approx 2500ml) the basin to the normal operating level. Initially this may cause the ATO to top up to replace this volume - this in unavoidable. In his instance, lets assume tank volume 170 litres, then ATO will add approx 1.75 litres when Clarisea first installed, so the salinity  will dip about 1%. On larger tanks it is even less.
 
When at normal operating level, the float switch operates over a very small range, so each time the fleece advances, there is only a very small change in water level  (SK3000 approx 85mls and SK5000 approx 120mls). This small change will have no effect on salinity and was part of the design criteria for Clarisea.
 
When it comes to fleece changing, the increased volume of the system will be returned to the sump and the sump will have an excess of water (about 1750ml in this example). However, after changing the fleece, this excess will quickly be taken up as the fleece blocks and water reaches normal operating level - so this will also have no effect on salinity.
 
So the only time salinity may be affected slightly is when first installing - if this is a concern it could be useful to coincide install with a water change and add an extra 1.7 litres of old water (2.5 for SK5000) to the tank at water change to allow for the Clarisea volume that will be taken up.