Pool debris problem.

[Jackson Ave]

Hello pool community, I have a problem that I can't figure out with my pool. We bought our home with maybe a 25 year old pool and never met the sellers for information on the pool. In the last year or so, we started seeing this material that looks much like sand coming back into the pool. So I thought that there must be a problem with our Pentair sand filter. So before I replace my sand filter we hire a company to verify that there are no leaks in our plumbing. They tell me that the pool plumbing must be good, no leaks that might allow dirt from under the pool, into the pool. So I buy a new sand filter and have the same results. I used glass pea gravel at the bottom of the sand filter and glass media instead of sand, thinking that some how it is sand getting back into the pool. The debris does not get the water cloudy, water stays pretty clean. So if my sand filter does not run for the day, I won't see this material on the bottom. Help.

[RDspaguy]

Once the laterals in the filter break and allow sand into the pipes it can build up in them quite a bit before any of it comes out into the pool, and can continue coming out long after you put in a new one.

[Jackson Ave]

That is a reasonable response, but the laterals were never broken. They were in perfect shape. It is a mystery to me where this debris is coming from. It only shows up in the pool if the pool filter is running.  

[RDspaguy]

Maybe @Pool Clownor @jimmythegreekhas some idea. Pools are not my specialty.

[Pool Clown]

Was the backwash valve replaced when you replaced the filter? Or are you using the same one?