I'm new to this forum, and I am absolutely not even close to being remotely expert in pool-related things, so be gentle with me!
We moved into this house in SoCal about a year ago, and it came with a pool and hot-tub, which is great. It's about 12,000 gallons. Last year everything ran fine. Then I made a huge error by laying sod close to the long edge of the pool. This then saw me have an infestation of springtail bugs, so a few months later I ripped up the sod (grrrr!) and while that area was just dirt for a few days as we waited for the new surface to arrive, we had tremendously windy weather (typical). I woke up one morning to the bottom of the pool being basically covered in dirt. I hooked up the vacuum (the one that goes into the main filter) and cleaned the whole thing. Obviously, the filter was now clogged with dirt, so I had to clean it. From that moment on, I seem to be getting fine dirt particles in the pool after the filter has been running. I've made sure it is when the pump is on by vacuuming it thoroughly (using a stand-alone vacuum with its own bag, not one connected to my filter) and the pool does not get dirty when the pump isn't on.
Once the pump runs, dirt gradually begins to build up on the bottom of the pool, and the location of the dirt and where it ends up settling is consistent with the angles from the jets. Obviously, the longer the pump runs, the more dirt accumulates and, after roughly the three-hour mark, the pool could be considered un-swimmable and needs a vacuum. I no longer use the vacuum connected to the filter and always use the stand-alone vacuum.
Obviously, my immediate and terrifying thought is that one of the lines under our back yard has a hole in it, and that's where the dirt is coming from. There are no obvious air-bubbles coming from the jets going into the pool, I don't seem to be losing water (I have yet to do the bucket test, but on cold days, I lose virtually no water), and you can't really see the dirt being pumped out, it just builds up over time. I cleaned out the main filter at the weekend (which had a considerable amount of dirt clogging up the filter 'bags' for want of a better word. I removed each filter 'bag' (a photo is coming to explain what I mean) and rinsed it off, and I also examined each one closely to see if perhaps dirt was being recycled from the bottom of the main filter via a hole in a filter 'bag' - I found that two of them have frayed material on one of the corners; only small, but I'm wondering whether because of the pressure being pumped through, this is enough to allow dirt particles to escape?
Any thoughts or insight would be greatly appreciated. I'm going to replace the damaged filter bags and see if that fixes it. If not, the only other conclusion I can come to is that one of the lines is damaged, which makes me go pale at the thought of the cost and disruption involved to get that fixed... or are there cleverer ways of finding and fixing underground leaks these days than ripping up a concrete back yard?