zimm and karmabiker: I understand. Is it normal for a pool like mine to need so much SLAM-ing when it used to look like a swamp? Sorry the pics aren't there, I arranged them in photobucket after I posted them and it must have broke the link.
I am at week 7, Dash. The Pool People wasted 5 precious weeks doing it their expensive, ineffective way. Cost me $1,300. Granted our pool had been abandoned for almost 3 years and had more than a foot of sludge at the bottom on the entire pool. So if you are at week 2 only, you are doing great. I got to the cloudy stage and fired them and have been making massive progress by myself and with the help of TFP site and good folks. Our water is now almost crystal clear. Keep slamming and don't look back. Surely your bleach and test kit is much cheaper than lining the pockets of the pool store....
I'd remove the multi valve and see if the stand pipe is broken. You may also have broken "fingers" (I don't know what the proper term is) at the bottom of the stand pipe.
You may want to empty the sand out and inspect fingers.
They are called laterals but we all know what you're referring to. And yes as they age they can get brittle and if they start to crack they can let sand get past and back into the pool.