RODI flush valve hissing

[NathanH]

Hey guys I got a BRS 4 stage RODI filter with a used tank I just bought. I replaced all cartridges, resin and membrane today. It seems to be running fine, there are no leaks. I'm seeing between 2-5TDS pre DI and 0 TDS after DI stage. My only concern is that there is a hissing sound coming from the flush valve. I uploaded a video of the sound, just wanted to make sure it's normal or if there is something I need to change. It doesn't make the sound while flushing, only while purifying water.

 

[lapin]

I must be deaf I dont hear any hiss

 

[KStatefan]

Water going thru the orfice

 

[NathanH]

Water going thru the orfice

Thanks, other filters (nonRO) I've had are silent but this is the first one with a flush valve like that so just wanted to make sure it was normal.