Cloud of dirt from returns for 5-10 seconds at pump startup

[MaxAcceleration]

Hi, I just opened my pool this week - opened it before the water temp hit 50 to beat the algae. The water is looking clear/good and my chemicals all look good (30cya, 6 FC, 0 CC, 7.5 PH 80 TA, 30 borate) but when I first turn on my pool pump in the morning it emits a stream/cloud of dirt from the returns, which stops between 5-10 seconds. What could be the cause of this? I've backwashed/rinsed twice this week and the sight glass turned brown so I know the filter is capturing dirt. The pump ran for two days (8 hours each day) and still gave me the dirt cloud, so it's not a lack of proper rinsing issue. I'm not getting any sand in the pool so I think my laterals are good. I normally let the timer turn, but this week I've been manually turning it on - so maybe this is normal and I've just never noticed it before? Any thoughts?

 

[Texas Splash]

If you are 100% sure the cloudiness is not algae, then it would make sense the problem could be filter related. For peace of mind, you might consider doing an Overnight Chlorine Loss Test first just to be sure there are no algae issues. If you pass the OCLT, then it's time to get in that filter and check a couple things like:
1 - When is the last time the sand was deep cleaned? Might be time.
2 - Anything odd at the multiport valve (MPV)? No water leaking out to waste when in filter, or any other odd behaviors in different cycles?

 

[borjis]

I had this happen once. It was actually sand.
I had a suction side leak and lost prime every day. By the time the pump primed and starts moving water a bit of sand would belch out.

Fixing the suction leak made that stop.
I think one of the laterals was fractured though. It only spit some sand when priming. Sold that property a few months later. Never addressed the lateral