There have been a lot of threads with advice about building a RIMS system but not so much about how to use/troubleshoot. I thought it would be worthwhile to have a thread dedicated to the clusters experienced RIMS users have already worked out. I'll go first...
Problem: stuck mash
The first time I used my system with grain, I ran it with the pump wide open at ~ 6GPM. Within 10 minutes, the pump was screeching as I had compacted the grain bed into an impenetrable slab on concrete.
I rinse and soak ~ 2 quarts of rice hulls for about 10 minutes. With the pump turned off, I add the hulls to the grains and stir for a few minutes. I let the grain bed settle for ~ 5 minutes and then turn the pump on low. I gradually increase the flow rate to ~ 2 GPM and have not had any additional issues with stuck mashes, even when brewing with a sizeable amount of rye. I determined the flow rate at 2 GPM through trial and error, but also by watching the fluid level in my sight-glass. The level starts to go down as your mass is sticking but will rise as you lower the flow rate.