So I recently bought the Thermo 850, and shared this on my 'setup thread', but decided it was relevant to here (I only found this thread earlier today.. What a read!)....
I like the design, size and idea of this filter, and not having to have the heater in the tank is great, however, I am getting air trapped, which is hitting the impeller, and coming out the outlet... At first I thought it was just that it was new, and things needed to settle, and the air will work its way out the system, then it seemed to get a bit better, but still did it every 5 to 10 mins, just a little burst of air. After doing the water change yesterday, it seemed to be doing it far more, and with a greater length of time per burst too... I hadn't touched the filter during the water change, so was nothing directly to do with that. This morning after some rather lengthy ones, I decided to look into the inlet pipe to see if I could see any air coming in that way? Nothing! Switched everything off including the heater, and noted that some air popped up into the outlet pipe. I first tried the pre starter a few times to see if that would maybe shift any trapped air, and a little more came out, but not much. So I started the filter again, and suddenly had loads of air bubbles being blasted up the outlet pipe. After half a minute it did settle down. I also leaned the filter to one side and every time I do, I get another stream of bubble going up the outlet. Again, at first I thought this was just some trapped air, as it settled down far better for a while afterwards, and while it is now much much better, I am still getting the odd small burst happening.
So when its all running fine, it seems great, and I can only hear a low hum when sat next to the tank (not much more than the Eheims I used to have), but this air purge is bothering me, especially as I am concerned it may result in the heater overheating?!
To me, it seems that either it is managing to draw air in through the main seal (though no water can be felt anywhere around the outside of the canister at all), or it has something to do with the primer. I'd actually like a pre filter for it that didn't include the 'starter' valve?
Cheers
G!