Green Pool with new sand filter

[Double Del]

Hello, this is my first post.

I let my pool get very green and got tired of dealing with DE all the time so I installed a Sand Filter. It's a Hayward 30" top mount 500lb capacity filter with a 1hp motor. Our pool is plaster resurfaced with fiber glass and holds 25000 gallons. Last night my FC level was about 8 and this morning it is at 0. My current test numbers are as follows:
FC 0
PH 7.2
TA 150
Calcium hardness 350
CYA 110

Thanks for any advice on shocking and getting clear water again.

 

[JohnT]

Welcome to TFP!

Here are some articles that will help you out, probably in the order I list them:

Chlorine CYA Chart You aren't going to like what you see in this one. Your high CYA is going to require either draining to reduce it or very high chlorine levels to overcome the effect of the high CYA.

Defeating Algae

Turning Your Green Swamp Back into a Sparkling Oasis

Shocking Your Pool

 

[jblizzle]

Welcome

I agree with everything John said.

Seems like a lot of people have been coming to the forums in the last few days with a CYA of 110+.

What test kit do you have? One suggestion would be to do the CYA test with a 50/50 mix of pool and tap water and then double the CYA reading. This can help determine the CYA level since 110 is on the edge.

Given that it is so high, you would be best served by lowing the CYA level. Your options to do that are replacing 50-70% of your water or hiring a compnay to do a Reverse Osmosis treatment on your pool (this can be $300-$400).

 

[Double Del]

Thanks for the welcome and replies, I have the Leslies DPD test kit, I bought the wrong one without the FAS portion. Its item 81-330. Can I buy the FAS powder and reagents or should I return the kit and get the right one? I just added 8 gallons of 10% chlorine.

 

[jblizzle]

You will likely not be able to find the FAS-DPD test locally ... it is like the holy grail or something So returning what you have may not help (or be possible if you have used it).

You can order just the Taylor FAS-DPD test (one place is here and the shipping is fast http://tftestkits.net/Single-Item-Tests-c6/)

EDIT: If you are planning to drain 50%+ of your water, there is no point wasting your money by dumping in all that chlorine.

 

[Double Del]

Ok Thanks!
Another thing I'm not sure about is my sand filter. The pressure at start up is 10psi and hardly goes up at all even after 24 hours of operation with a dirty pool. On my DE I had to backwash every couple hours when my pool was dirty. I added DE but then the pressure when up to 22psi within 30 minutes and I had to backwash. I guess I added too much DE. The water looks clean coming out but is fizzy like it's been mixed with air. Here is a picutre.

 

[jblizzle]

Sand filters are just a little slower at filtering out the debris (especially if you have a large pump with a lot of flow). Just backwash when your pressure goes up 25% of your clean pressure. So if your clean pressure is 10psi, backwash between 12-13psi (obviously if you add DE that will change things).

 

[Double Del]

After I backwash the filter the water comes out air free then after about 5 minutes is starts coming out fizzy looking and the pressure drops about 2-3 psi, Im thinking maybe the sand is channeling?

 

[JohnT]

After I backwash the filter the water comes out air free then after about 5 minutes is starts coming out fizzy looking and the pressure drops about 2-3 psi, Im thinking maybe the sand is channeling?

Sounds more like a pump issue. Is your pump strainer basket staying full of water (no air)?

 

[Double Del]

Thanks for the reply John,
I don't have air in the skimmer basket. When I backwashed because I added too much DE to the Sand Filter, I saw no green whatsover in the discharged water like I did when I backwashed the DE filter. Is that normal?