I've been trying to troubleshoot my sand filter today, at least I'm learning a little bit about how it works. It has a side installed MP valve. I know large particles are bypassing the sand and re-entering the pool. Before I found this site I added CYA directly to skimmer and noticed it on my swim up ledges under the returns. Today I took apart the filter and used a wooden broom handle to break apart the sand in case there was channeling. I added a small amount of CYA directly to skimmer and it is still coming out of the returns. What are my potential issues? Should I take apart the multiport valve and inspect the spider gasket? I'm not sure of any other way debris that large could bypass my filter. Thanks in advance for any guidance here.