Brown spots on deep end of vinyl pool

[ladybug]

First, let me start by saying, Thank you!!! I had a green, cloudy pool that I could not clear up and with reading the forums and doing what was said, SLAMing only once got a crystal clear, beautiful pool.

Now with my problem. I have brown spots on the deep end of my pool. I have a vinyl pool. I brush the spots, put straight granular chlorine on the spots, let sit for 20 to 30 minutes, then brush and vacuum. They go away but the next day they are right back. All of my water test values are good and the only place these spots are are in the deep end. They seem to be where the slope from the back wall meets the hopper (2 there) and the slope from shallow ends meets the hopper (1 there).



___________**__________ ** Skimmer
| ? | # returns
| Deep ? Shallow | ? spots
|__?____________________|
# #

Hope this illustration makes sense.

Any suggestions are greatly appreciated.

Thanks!!

Ladybug

I have an 18 x 36 pool and per pool specs 22,300 gallons of water.

 

[duraleigh]

I would be concerned that the granular chlorine is too harsh to leave it for 20-30 minutes and would make matters worse.

How large are these spots? I assume just brushing alone will not remove them, correct?

 

[ladybug]

No, brushing does not remove them. The spots are about the size of baseballs.

My values are:

FC: 10.6
Total chlorine: 11.1
Combined chlorine: 0.5
pH: 7.7
Hardness: 139
Alkalinity: 84
Cynanuric acid: 90
Copper: 0.3
Iron: 0
Borate: 5


Using a sand filter and a 1.5 hp pump.