My sand filter sucks, new filter options?

[Unabomber007]

I have a brand new sand filter and it just WILL NOT filter for anything. I have a pretty dirty pool with dead algae. I get 2-3 widths of vacuuming and the returns start pouring out green water during the vacuuming process. Backwash---rinse----filter and get 2-3 more widths. Repeat this cycle 6-8 times and get 3/4 of the pool done. Then......I have a cloudy pool and need to put more water in.

Previously, I've added DE to the sand filter. I have added like 3 full cups to get 1PSI increase. Then after a day or two.....the pressure will shoot up from 13PSI to 20PSI. Apparently, my sand filter doesn't like DE for some reason.

Run the Aquabot Viva (2 micron filtration NOT) and it just pours a steady stream of green out it's exhaust outlet.

So unless someone has any advice....I'm in the market for a brand new DE filter and pump. My pump is fine, but I'm thinking it would be in my best interest to replace it all at once. The current pump is a very old Hayward (I think) and is so worn I have no idea of model or HP rating, but it's one speed.

My pool is an 18 x 38 rectangular inground vinyl. The deep end is maybe 8 to 10 ft deep (not sure).

Can anyone recommend an APPOPRIATELY sized filter and new pump?