Frustrated with poor filtering performance and algae(?)

[chatko]

Pool temp: 80
FC - Free Chlorine: 11.5ppm
CC - 1.0ppm
pH - 6.8
TA - 100
CH - 300
CYA - 23-24
All measured with TF-100 kit

Problem #1: Yellow/Brown build up on pool floor. I vacuumed pool bottom to waste last week and now its all built up again, all the while maintaining 10ppm CL. (attached pics) Do i need to shock again ... sigh (how high)?

Problem #2: Pool filter lets through visible particles. After I vacuum up some leaves/dirt and i'll see small pieces of debris coming out of returns and collecting under the returns on the pool floor. It makes filter setting kinda useless. I've attached filter bags to the returns for the present.

A bit of history on this one: I've changed out the sand (twice, changed pool sand brands each time). When I did this I inspected the laterals and didn't see any damage. The one part I don't quite understand is the junction between the filter valve-head the tube which goes down to feed the laterals. I can't tell how snug that connection is as there is no way to access this when i bolt the filter head on. Could a broken/ malfunctioning filter valve-head be causing these problems?

Currently use Chlorine pucks in a chlorinator after the filter.

Thanks for your help,

Chris

 

[Richard320]

Pool temp: 80
FC - Free Chlorine: 11.5ppm
CC - 1.0ppm
pH - 6.8
TA - 100
CH - 300
CYA - 23-24
All measured with TF-100 kit

Problem #1: Yellow/Brown build up on pool floor. I vacuumed pool bottom to waste last week and now its all built up again, all the while maintaining 10ppm CL. (attached pics) Do i need to shock again ... sigh (how high)?

You don't need to shock again, you need to shock still. Around these parts, we call it SLAM. Shock Level And Maintain. It can take weeks in a bad case, certainly several days in almost all cases. You need to keep the FC level up until that CC level is down below zero and you lose less than 1 ppm FC overnight. The water looks clear, so there's one out of three.

I can't help you with the sand filter problem, since I've never dismantled one.

 

[chatko]

Ok thanks, i'm going to try this SLAM ... one question:

My CYA measure read ~24 and FC was already at 11ppm, so according to the Chlorine / CYA Chart am i not at about shock level already?

 

[Richard320]

Ok thanks, i'm going to try this SLAM ... one question:

My CYA measure read ~24 and FC was already at 11ppm, so according to the Chlorine / CYA Chart am i not at about shock level already?

Yes. But the CC level is too high, so you need to maintain it at that level for as long as it takes. Frequent brushing and checking hiding places like inside ladder uprights and beneath ladder steps will also help speed things along.

 

[Zadd]

It sounds like the sand has channeled and is now allowing particles to flow directly to your laterals and back into the pool. Sand really does not need to be changed but does need a little care once a year. Try running your hands through the sand to break it up. Careful not to disturb any brittle laterals The filter should be filled up to about 14-12 inches from the top with sand also.

If you are catching sand getting back into the pool that indicates a broken lateral.

 

[heatmisr]

Your pH is too low. Shock levels of Cl give false high pH readings. If your FC is really 11.5 and your pH is really 6.8, your pH is way too low. Your TA is pretty much in range, but you need to raise your pH right away so I would use borax. Using borax would raise the TA some, but the benefit of raising the pH quickly outweighs the slight bump in TA you will get.

 

[chatko]

An update:
First I vacuumed (to drain) the largest deposits of algae/dirt/etc

Next upped the PH to 7.3

Next I added liquid chlorine (10 Liters ~10%) + 3 cups of granulated chlorine. I ran the filter for a few hours and measured:
FC:30ppm CC: 0.5

This morning I scrubbed the side of the pool and measured:
FC:29ppm CC: 0.5 Added another cup of granulated chlorine, left filter running and went to work.

How long do i need to keep this going? (seems like my FC is way too high, but it was already high to start with)

 

[scott.MI]

If your CYA WAS at 23-24, and you added 4 cups of granuals..(assuming it was dichlor) you can assume your close to 30 now...

Let your FC drop closer to 12 and then start your tests to see if your done slamming. Keep brushing while your FC is over 12 while you wait for it to drop.

CC is 0.5 or lower;
You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
And the water is clear.