To deep clean the filter:
Unplug or turn off the pump
Close both valves to keep the water in the pool
There's a clamp below the multiport valve that goes around the neck of the filter body
It's the clamp with a bolt and nut on both sides of the filter, right above the wider part of the filter (filter body)
Undo both sides until the clamp is loose enough that the multiport valve assembly can lift straight up and off the filter body with the pipes still attached
Undo the clamp completely if necessary
You'll be undoing that clamp below the multiport valve and then lifting the entire multiport valve straight up
If you can't lift it straight up, you may need to loosen the clamp on the pipe that comes from the pump and remove it
The pipe going to the pool should be able to stay connected, if not both pipes.
Once you have it off, put something over the stand pipe (it's in the middle) so no dirt will enter it. You can stuff a rag into it or something like that.
Re-read the description of deep-cleaning
Use a garden hose to flood the filter and start floating out the gunk
Gently lower the garden hose into the sand with water running out of it
As you get deep in the sand, be especially gentle
From reading that article, you'll see that there are laterals like the spokes of a wheel, down in the sand
You'll probably feel them with the end of the hose as you dip it in and around the sand
Be gentle as you feel that you're getting to the bottom
Do everything slowly, deliberately, so that the standpipe in the middle stays put
Bring the hose back up and insert it down into the sand in a different spot, always being gentle, especially near the bottom
Keep doing that, lowering the hose down into a new spot, always being gentle, until the water runs clean
Then remove the rag or whatever you covered the standpipe with
There is probably an o-ring inside the multiport valve bottom opening. That o-ring seals against the standpipe
If you have some silicone o-ring lube, put some on that o-ring, KY jelly is close enough
If the o-ring still has silicone lube on it, it's preobably good enough, but use your finger to make it even
Don't use grease or Vaseline
Gently carefully lower the multiport valve over the standpipe and onto the neck of the filter body
Replace the clamp that holds it on
Partly tighten it, egually on both sides
Gently knock it into place (rubber mallet is best, or a piece of wood)
Tighten it some more, equally on both sides
Knock it gently into place again
Finish tightening it, equally on both sides
Re-attach any pipe you had to detach, and filter is ready to go
