draining pool due to high CYA and CH

[tedinelkgrove]

I am draining my pool today. ~13800 gallons. I will probably drain about 3/4th of the water as CYA is 300 and CH is 750.

After I refill, what order should I add chemicals. How much Chlorine for a 13800 gal pool?

 

[257WbyMag]

Welcome to TFP!

Home page on the left side. Click the 'Pool Calculator" link. Plug in your gallons at the top and enter your values in the fields. It will tell you exactly how much of what to add to your pool. There is no way of knowing how much chlorine you will need in your pool until it is refilled and the new CYA level is known.

What sort of test kit do you have? I don't know of any test kit that can give a CYA level reading of greater than 100 ppm. If you are using a pool store to test your water for you, you need to invest your own high quality test kit. The TF-100 (link in my sig) is the best deal on the market. The Taylor K-2006 will suffice too. Pool stores are notorius for bad test result variances. Their goal is to sell you products and not to keep you trouble free.

Be careful with big time pool draining projects. If your water table is high, you can really run into problems by draining or nearly draining your pool. If there is any question about where your water table sits, it is best to drain in stages rather than in one fell swoop.

Have you read the pool school articles yet? There is information in there that is indispensable.

 

[257WbyMag]

Ted,

Also if you would, please create a signature line in your profile that includes what type of pool you have (in-ground, above ground, vinyl lined, gunite, salt water, etc.), filter type, gallons, and whatever else you have related to your pool. It will help people understand your situation with regard to any problems that you may be having. It is also nice, although not manditory, for you to put your city and state in your profile as well. There are lots of problems that we see people having that are related to the area that they live in. An example would be high calcium levels in the desert southwest.

We ask that you limit your signature line to five lines total. Thanks!

 

[tedinelkgrove]

Thanks for the welcome. Just bought the home a month ago. First time pool owner. It is obvious previous owner loved the di-chlor tabs due to high CYA and CH levels. Pool was built in 2006 so I assume he used the tabs from day 1. I switched to bleach after being introduced to the poolschool.

I have the Leslie's DPD-Complete Poolcare Kit, and the FAS-DPD Chlorine kit fron TF Test Kits. I determined CYA by diluting sample 2x and estimating the results by doubling the value obtained. It was lower than the 100 mark with the dilution, meaning that it was about 150ppm. So my CYA value of 300 is a guesstimate.

I have been reading poolschool and practicing the BBB method up to this point. The pool calculator has been my life saver. Just wanted to drain and get those CH and CYA values to mangeable levels.

I believe our water table here is pretty low this time of year. Plus my house is on an elevated plot. I am adding water with the auto-fill as I drain. Even though the flow rate out is significantly more than what is coming in, I figure the extra diltuion wouldn't hurt...except my wallet when the water bill comes.

 

[257WbyMag]

Okay, very good. Then once your pool is refilled, check the CYA and with that, you will know how much bleach to add to get your FC where it needs to be using the Chlorine / CYA chart. Then you can add chlorine and adjust your pH and all that other good stuff.

 

[tedinelkgrove]

Thanks for the prompt replies and the advice. This site is wonderful. I'll post my new numbers after the refill. I assume sometime tomorrow

 

[257WbyMag]

No problem. You'll be swimming by lunchtime on Friday.

 

[tedinelkgrove]

Still waiting for the refill to finish. It is almost to the tile line

Will I need to add shock amount of sodium hypochlorite to the pool being so much water was replaced? I replaced about 75%.

 

[duraleigh]

Will I need to add shock amount of sodium hypochlorite to the pool being so much water was replaced? I replaced about 75%.

Possibly. Post your numbers (you can do so anytime) and you'll get lot's of help. Hopefully you won't need to shock since you seem to have done this very smoothly with little delay but the test results will tell us/you.

 

[tedinelkgrove]

The results are in:

CYA = 180
CH = 300
TA = 120
pH = 7.8
FC = 6
CC = 0

Not sure what to do about CYA. How can CH drop over half but CYA doesn't. I also diluted sample and doubled result, came up with 180 again. Any suggestions?

I plugged the numbers into the pool calculator and added a gallon of NaOCl (sodium hypochlorite) since I don't know whether to believe the CYA result. Do I need to shock?

 

[VoR]

300 to 180 is pretty close to half, especially on a test like cya.

How'd you drain it so fast? I'm still working on mine (since Tues evening) but I'm just using hoses and gravity and watering our citrus trees since we're under a drought still.

 

[tedinelkgrove]

I rented a submersible pump and 150 ft of hoses. It drained 3/4 of the water in about 3 hrs. Rental cost with 3 hoses was $50. Refill took about 20 hrs.

I expected the CYA to drop down to about 100 or lower. I retested and I am going with a CYA of 150 ppm. Based on the values entered into the pool calculator, at least my CSI is only 0.18, and -0.08 once I adjust pH to 7.5.

I'll do another drain and refill after next week. Friends and family coming until July 16th. They would freak out if I closed the pool for a day

 

[tedinelkgrove]

I assume I should leave my TA alone since that number is being elevated with the high CYA?

 

[Butterfly]

Yes, your TA is fine where it is.

 

[tedinelkgrove]

I just checked pH and it is off the chart today. I would guess 8.2. I entered it into the pool calc and I added recommended amount to bring it down to 7.5. Does the high pH indicate a problem?

 

[reebok]

is your fc above 10? if not you definitely need to get the ph down.

 

[tedinelkgrove]

is your fc above 10? if not you definitely need to get the ph down.

FC is 15. After adding HCL and retesting an hour later, pH is now at 7.5.

 

[reebok]

ok, well, fc above 10 gives a false high ph test result. for future reference (though you shouldn't need it if you follow the chlorine/cya chart if your ph is low (esp less than 7.0) but your fc is over 10, your ph is really low and you should raise it.