I'm on my 3rd season of owning my pool (estimated build around 1999). Last year I discovered adding DE to my sand filter greatly improved its filtering ability, went from kinda clear to crystal clear with the addition of DE. This year when opening it the water just wouldn't get anywhere near clear without using the DE, so I opened up the filter and rinsed it out and didn't really get much gunk out so I'm contemplating replacing the same to start new. I know many people on these forums say you really should never need to replace the sand but in my case I think it would be beneficial.
On to the questions..
1.) I have a slide valve currently and it seems about every year I have to replace the O-rings on this thing. Every spring I check them, clean off and add lube and reinstall. The bottom O-ring on the slide valve is always stretched out and sometimes torn. It doesn't get used very often due to not having to backwash regularly (maybe once or twice a season if that). I've read that most if not everyone recommends a multi-port valve over a slide valve. Would this be a good idea for my situation? I'm not really sure why the O-ring keeps tearing or wearing out, so I'm not sure if there’s something else causing it or if its normal operation for these slide valves. One more point to add is that the way my backwash line is plumbed is goes into what I would call a pit next to the pool equipment and just goes back into the ground (no backwash hose or anything). For this reason I have no idea of the water coming out of the backwash line is clean or not because its being pumped into dirt and just filling up this "pit".
2.) When opening my pump basket the water immediately goes down and starts a sucking sound, to me this doesn't sound right but I'm still a newbie at this. Does this sucking indicate a leak somewhere?
adding pics below so you have a better understanding of my setup.
The metal box mounted on the wall on the right is an old Oxidizer that was already disconnected when we purchased the house.
This is where the water comes out, as you can see theres no way to tell if the water coming out is clear.