Do you need to change the sand filter if there is black dirt in pool day after vacuum it out?

* If the black dirt is debris that was vacuumed up from the pool, then a simple backwash of the sand filter should be sufficient to remove it.

* If the black dirt is due to a buildup of algae or bacteria in the filter, then you may need to chemically treat the pool and filter and then backwash the filter to remove the dead algae or bacteria.

* If the black dirt is due to a problem with the filter media (such as a broken or cracked sand filter), then you will need to replace the filter media.

To determine the cause of the black dirt, you can:

* Inspect the pool water to see if there is any visible algae or bacteria growth.

* Test the pool water to check the chlorine and pH levels.

* Inspect the sand filter to see if there are any cracks or breaks in the filter media.

Once you have determined the cause of the black dirt, you can take the appropriate steps to correct the problem.