I own a 2006 SD Cameo 880 series spa. I have been experiencing a problem where the heaters will not come on due to a low flow condition. I have done all the obvious things - replace the filter, tried to clear the lines of any obstructions... it is very interesting that the heaters will work (low flo overcome) if I block the "second" inlet line to the bottom of my tub (evidently there are 2 outlets from the circ pump - and only one goes through the heaters). By blocking the one inlet I can heat the tub. Suggestions?? Is there a permanent screen - at the heater box?? - or something similar that could cause a partial blockage - and the low flo condition that I am battling??