very fine particulates passing through filter

I have a 16x36 inground vinyl pool - controlled with chlorine - the usual shallow and deep ends.
Filter is a Pentair Tagelus TA-60D - 325 lb sand filter
been doing the pool store runaround this year but all chem levels seem to be adjusted correctly now
for two years I have had a problem with particulates being blown into the pool
this is not sand- it will sediment out of solution and collect like sand on all the seams and creases
but if you touch it- it is so fine you cannot feel it- no grit, no texture at all
it simple disappears back into solution
it is a grey color
if I vaccum it up, it is blown back into the pool as fast as I remove it as if the filter did not even see it
I replaced my sand yesterday-- no difference today
any ideas what this is? How to get rid of it?

How big is your pump? A lot of times people have pumps that are too powerful and they simply force stuff through the filter media right back into the pool. Can you actually see the stuff coming out of the return jet or does it just reappear on the bottom of the pool? By the way, there is no reason to change sand. It does not wear out. Sometimes you have to top it off a little but not replace it. I have had the same sand for 12 seasons.

OR --- It might just be dust and dirt. My liner pools have always had the same situation. I can vacuum and get the floor clean but that is only because the dust is suspended in the water from movement. Then, it settles right back down into the lines on the floor caused by the liner seams and also where the pad underneath the liner is taped together. No matter how clean I think the pool is, those "lines" always reappear. I don't think there is much you can do about them. There is no possible way to get rid of every single speck of dirt/dust in a pool. Once people are in and the water is moving, it all goes back into suspension so you can no longer see it. No big deal.

Pump is Magnatek 1.5 hp
I cannot see it being blown in- it just appears as it settle out of solution
it is predominately in line with the return jets
and there is quite a bit of it-- all seams with maybe an inch wide and dead spots in the pool flow collect about a foot square
all within 30 minutes of vacuuming clean

Magnatek is the MOTOR on the pump, not the pump.

It's very, very common to match an undersized sand filter with an oversized pump. When this happens, fine particles are blown THROUGH the filter, AND, sand tends to be blown OUT of the filter during each backwash cycle -- so the problem gets worse over time.

The immediate solution is to slow flow through the filter, by throttling a valve DOWNSTREAM of the pump.

The longer term solution is to (a) check and add more sand if needed,, and (b) replace the impeller with a smaller one. You can run a 1HP impeller with a 1.5HP motor with no problems, and only a slight loss of efficiency compared to a 1 HP impeller with a 1 HP motor.

But, to accurately size things, we'd have to known which PUMP you have, have a complete equipment list, and see some photos (you can mail them to poolforum@gmail.com) of your pump / filter / piping.