Dirt in Bottom of Pool Even After Vacuuming?

[spmurph]

For the past three seasons, my father has been having an issue with dirt (or something else) frequently gathering in the bottom of his pool. I went over to his house yesterday and he said this appeared despite running the vacuum (robot) this morning. He uses test strips, so I brought my kit and tested the water:

FC: 5
CYA: 45
PH: 7.5
TA: 140

It appears to only gather in condensed areas of the liner, such as wrinkles or divots. I told him to try a filter sock over the return to see if anything is getting returned through the filter (sand).

Any idea what this might be?

 

[OHcabanaboy]

It's more likely dead algae that the vac isn't picking up. Gotta use a skim vac to pick that up or keep running the pool bot with the pump on to get it suspended long enough that it cycles through the main filter.

I have the same thing right now and at the start of each season. I run the bot, stuff disappears only to reappear a short time after in any "crack" or wrinkle.

 

[spmurph]

It's more likely dead algae that the vac isn't picking up. Gotta use a skim vac to pick that up or keep running the pool bot with the pump on to get it suspended long enough that it cycles through the main filter.

I have the same thing right now and at the start of each season. I run the bot, stuff disappears only to reappear a short time after in any "crack" or wrinkle.

Thanks for the info! I will have him try that.

 

[mariane]

I also think it looks like dead algae that falls to the bottom. Does the robot have a tube that sucks the water up into the filter? If not the robot is just stirring up the algae and then it settles.
With CYA at 45, his FC is too low (should be 6-8) and the algae is still growing. He needs to do a SLAM SLAM - Shock Level and Maintain - Trouble Free Pool (check Pool Math to see how much FC needs to be PoolMath - Trouble Free Pool) and if possible vacuum up the algae by targeting those clumps. If he can't vacuum them up, then the process will be waiting for the filter to get rid of the algae. Brush the walls and bottom to stir it up after vacuuming.
Hope this helps.