First backwash after changing sand had lots of sand coming out of waste valve

[mikeb22]

I have a Pentair SD35 sand filter which I replaced the sand in. I used 100lbs of #20 silica sand as recommended. I also removed the standpipe and laterals and inspected, everything was fine. After putting back together and running a backwash cycle a heavy amount of sand was coming out of the waste valve. I have read common causes are cracked filter parts (were none), and too much sand (I used 100 lbs). Is sand coming out on the first backwash common? I did not try the filter position as I was afraid of putting sand into the pool.

 

[kellyfair]

Did you do the rinse setting after the backwash? Settles the sand down.

 

[kellyfair]

Also, did you cover your standpipe when adding sand?

 

[mikeb22]

I did cover the sandpipe (and the amount of sand was more than what would fit in the pipe). I did not rinse as I thought that should be done after the backwash for 4 mins and I was afraid if I ran 4 mins I would have no sand left.

 

[kellyfair]

You should always run on rinse after backwashing, for at least a minute or two.