1. After you backwashed the filter, did you switch it to "rinse" mode for a few minutes before going back to "filter", to wash the remaining sand out of the lines? If not, that's probably your problem. If so, then you meay need to look for a cracked or broken lateral in the filter. Does the sand spit all the time, or just for a few seconds after turning on the pump? Any visible air coming out?

2. Many things can cause staining, but I often have a yellowish tint to my stairs after the winter is over, but it's usually from leaves that have sat on the bottom of the pool and disintegrated over the winter . (My pool stays open all year, and my neighbor has a virtual forest in her backyard, so all her leaves blow into my pool over the winter. I usually wait until all the trees are bare before making an effort to get them all out, and usually don't get them all out until the water starts warming up.) Usually after a good 2-3 day shock, the yellowing goes away.

If not leaves, then do you perhaps have metals in the water? Have you tried taking your chlorine up to shock level for a couple of days to see if that makes a difference?

Janet