Need help, can't raise FC

[fezzer0014]

I opened the pool on saturday and the water was crystal clear. But there's something that looks like sand all over the bottom of the pool. No idea where sand would have come from, but similar beige color. My initial readings are below, and I have a ~20,000 gallon poured concrete pool with an Anthony Apollo 52 sq ft DE filter and a 1 HP pump.

FC 0
CC 0
TC 0
CH 200
TA 60
CYA 0

I got to work raising my CYA (got a little carried away and have it up to 50) and brushing and vacuuming the pool. By the time I finished vacuuming the pool was very cloudy and I haven't been able to clear the cloudiness and the sand keeps coming back on the bottom of the pool. Yesterday and again today I vacuumed the pool with the valve set to backwash thinking that will evacuate the sand. I've tried to SLAM but have had issues getting my FC levels up. I used the pool math and by adding 3 gallons of chlorine (I buy 12.5% liquid chlorine from a local pool supply store in 5 gallon containers) I should get up to a FC of 20. I just put in 3 gallons and took a measurement 20 minutes later and only read 3 FC and 1 CC. Since Saturday I've put in 20 gallons of the 12.5% liquid chlorine and I can't get my FC up high enough to SLAM. I don't believe that there's an issue with the quality of my chlorine as I was able to raise the FC level in the adjoined hot tub. The water is still cloudy but starting to clear a bit.

I've also had issues with the filter. It keeps getting clogged the pressure of the water coming out is relatively low and it's running at about 20 psi. If I backwash or open the filter or hose off all of the fins it gets better and drops to about 10 psi, but within a few hours creeps back up and the flow slows down.

I'm not sure what to do from here. I thought 10 gallons of liquid chlorine would have been enough to get through the SLAM process. Is my frame of reference way off? How much chlorine should I have on hand to get through the SLAM process? Is there something else I should be doing besides adding liquid chlorine

 

[mknauss]

Welcome to the forum!
The statement "I just put in 3 gallons and took a measurement 20 minutes later and only read 3 FC and 1 CC." implies you have ammonia. That occurs when you a bacteria gets in your pool water that consumes CYA over the winter and creates ammonia. Adding the CYA just fed it.
To check and defeat ammonia, if necessary, is to raise your FC in the water using enough liquid chlorine to get to 10 ppm using PoolMath. Circulate the pool for 15 minutes. Test FC and CC. If FC at 5 or below, add LC to get to 10 using LC, circulate for 15 minutes, repeat until your FC is above 5 ppm after the 15 minute circulation.
I suggest you read ABC's of Pool Water Chemistry.

 

[fezzer0014]

Thanks, I ran out and got a ammonia test and the color reading of my pool water and tap water are virtually identical. I'm assuming my best course of action is still to continue to add the liquid chlorine until I can get my FC up.

 

[Thomas89]

Hey Fezzer0014, let me know how this works out for you. I'm having the same issues with my FC level showing 0.

 

[fezzer0014]

Before heading to the store to pick up chlorine (this time getting another 15 gallons), I tested the FC today after my reading of 3 last night. This time it was at 9, and the water was definitely clearing up. There is a possibility that there was ammonia but with all of the cholorine addition it could have worked it's way out by the time I ran the test. I was at the point where I was looking at what was more economical between getting enough chlorine to hit the 10x ammonia ppm and draining and refilling from the hose. Looks like I'm back on track and I was able to raise my FC to the SLAM level this evening.

Would be interested in the feedback from more seasoned folks, but seems like if you're having a hard time increasing the FC, add the chlorine to get to the SLAM value every hour or so until you're seeing improvement. Also, make sure that you're getting good flow through your filter. I had to hose off my fins multiple times, but probably needed to do it more frequently to help filter the water and circulate the chlorine throughout the pool.