No FC - frustrated!

[nomorepoolstore]

A little background first is in order... We have an inground 22,500gal w/SWG, sand filter and a vynil liner and are located outside Nashville, TN.
Last year we converted to a SWG and had the best experiance ever!!! Highly recommended! Our costs were minimal and our testing barely wavered at all.
However, this season is another story... we started out with good readings and proper levels all around until recently. Over the past few weeks we have had little to no free chlorine and a combined chlorine of 3 reducing to around 1 in the past week. We have tried shocking with a non chlorine shock at high doses to break the mythical barrier as well as a chlorine shock at high doses of over 10 lbs at a time. The water gets a bit of foam on the surface and you get the idea that something is happening but the next days testing always resulted in a very low FC reading. Just as a note we are treating for phosphates as we had a high reading early in the season but now it's just a maintainance dose. Then we tried cleaning the sand filter now twice, thinking that maybe the problem is in the sand... and last night went straight to 10 bottles of chlorine bleach at 6%. This resulted in alot of fine bubbles and we thought that maybe this was it, placed the robot cleaner in to not only move the water around, but continually brush the walls. A few hours later my wife tested out of curiosity and had a reading of 5 FC and 5 TC which would give us a CC of 0.
This morning her readings were 0FC - 1TC ...
What should we do next, replace the sand; more chlorine ... Help please!

 

[zea3]

More chlorine is the answer. If you could post a complete set of test results we can help narrow down exactly what is going on in your pool. Have you checked the cell in the SWG to see if it needs cleaning?

 

[nomorepoolstore]

Yes, cleaned it twice and had it tested.
Size-22500
FC-0
pH-7.3
TA-100
CYA-70
Salt-3100
Temp-82F
SWG with a Vinyl liner

 

[Bama Rambler]

How did you get those results?

You need to shock the pool. What you're doing is throwing some stuff in there and hoping it works. Stop That!

Read Pool School on how to shock your pool and follow that.

 

[dmanb2b]

As in Bama's sig...suggest you are done shocking when 1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

Shocking with CYA at 70, means raising your FC to 28ppm and holding at that level until the 3 criteria above are met

 

[nomorepoolstore]

Test Kit ...
we have been using shocks (chlorine and non-chlorine at shock levels) and have just recently tried plain chlorine bleach to see if that works.
Given the prior results how many gallons of bleach should we shock with at 6% sodium hypochlorite to try and rectify the problem? The pool school suggests that I shock the pool to a level of 28 (given a CYA of 70) which is what we tried last evening, in fact I went 1.42 gal over the recommended dosage in frustration.
Should we do the same dosage again?

 

[Bama Rambler]

Which test kit?

To go from 0 ppm FC to 28 ppm FC it will take 7 large (182oz) jugs. At that rate I'd start with about 20 large jugs. You should add and test every hour until you pass the OCLT with the swg off.

 

[Butterfly]

You should CAREFULLY follow the directions in Pool School for How to Shock Your Pool:
Here's a link: pool-school/shocking_your_pool

Shocking your pool is a process and not a one-time event!

 

[nomorepoolstore]

If I understand this correctly, I am to start with an initial dose to bring it to 28, then use the additional bottles to maintain every hour along with testing until I reach the desired numbers... Correct?

 

[Butterfly]

If I understand this correctly, I am to start with an initial dose to bring it to 28, then use the additional bottles to maintain every hour along with testing until I reach the desired numbers... Correct?

Yes, initial dose to bring FC to shock level of 28.

You can test as often as every hour and raise FC back up to the shock level of 28.

Use the PoolCalculator.com to figure each dose.

[EXAMPLE: Let's say you raise FC to shock level of 28. An hour later you test and FC is 20.
You should add only enough bleach to raise FC from 20 to 28.

Wait an hour and retest and adjust back up to shock level. [End: Example]

Then, you maintain shocking until you meet the three criteria that show you are done.
See red lines in my sig.

 

[nomorepoolstore]

Success!!!
Although we do not have a test kit that registers over 5PPM we went ahead and added an additional 11.36gal of 6% bleach. This morning we had a FC and TC of @ 5PPM which gave us a CC of 0PPM ... though a bit hesitant to celebrate we were happy to see improvement. Being a hot sunny day @ 92 we let it go and tested this afternoon with the following results.
Thanks for your guidance!

FC-5
TC-5
CC-0
pH-7.2
TA-110

Now... on to the next question.
We have been told in the past that when it comes to a SWG you only want to use the liquid form of CYA and not the granular. Is there any truth to the granular form being harmful to the salt cell?

 

[Butterfly]

Granular CYA is just fine for any type chlorine source

I suggest you use the sock method to add the CYA.