sand filter problem.

I have a nicely sized sandfilter, 2 inch tubing, 1.5 inch hp motor and a 17000 gallon inground pool. I installed the filter last year myself (replaced a cartridge filter) and filled the filter with the zeobrite/zeosand (can't remember exactly which) sand. I used half the required amount for normal sand , as directed by the instructions for zeo. The filter is a hayward filter, the switch and piping connect on top.
Here is the problem; Every time the pump switches on for its 8 hour run, I see a puff of cloudy water coming out of the returns into the pool. It is only briefly. It seems to disappear almost right away but the water is a bit cloudy after this until the pump has run for a while.
It started doing this after I changed the filter so that makes me think it's something with the filter.
any clue why ? The new filter was installed months ago and has been backwashed several times so I would think any impurities in the sand are now gone.
and yes, I do use Rinse after backwashing.
Remove NO-SPAM from email address when replying
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Site Timeline is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.