We presently have two problems going on with our pool. The DE blowing back into the pool is the more important of the two. When the filter turns on, the earth blows very heavily from one return line and a little from the other. It last a 45 seconds or so. This happens when ever the pump is turned off, whether for 8 hours or 5 minutes. We have replaced ALL the grids with unicel grids, we have replaced all O-rings and we have replaced the multiport valve. My husband is ready to buy a new filter (this one is @7 years old), but I thought I'd inquire here before potentially wasting money. There are no visible cracks in the manifold or the outlet elbow. I am thinking of replacing each of them next. What else could it possibly be??
The second problem that I am not worried about right now is a suction side air leak, all gaskets and O-rings again have been replaced and well lubed with Magic Lube. We removed the heat pump from the system which was likely to be 95% of the problem but still not 100% fixed. Right now the DE is the biggest problem. I'd like to fix it before the summer is gone. Thank you for your help.