Before I drain a portion of my pool water

[jgofnj]

I have a few questions before I go ahead a drain my pool water. Before I discovered this great site, I was ignorant and was using the hockey pucks in an automatic chlorine feeder. As a result, my CYA is around 100-110 ppm. I know the most effective and efficient way to lower the CYA is to drain some water. After reading up on draining the pool, I had some concerns because I have a vinyl liner pool. I am OK with taking the slow approach which is to dump a little then fill with fresh water and repeat as necessary to avoid damaging the vinyl liner. But my question is

1) Should I shut off the skimmer lines and drain from the main drain only so that if I reduce below the skimmer line, it does not take in air?
2) Or do I leave the skimmer open and not worry about going just below the skimmer opening?
3) Or do I just drain only enough to not go below the skimmer level (which is only about 5-6 inches)

Thanks.

 

[linen]

Since your cya is so high (how did you determine your value?), you are going to have to replace more than 1/2 of your water if you do it at one time to get down to ~50 ppm cya. Unless your ground water is really high right now, you should be able to safely drain down to 1 ft of water left in your shallow end. If you can isolate your floor drain, I would just pump form there.

 

[jgofnj]

How did I determine my CYA level of 100-110? Good question. Actually when I ran the test using the TFP test kit I got a reading of 80-90 range. Forgive me for saying this part, but I took some water it to the pool store to see what their reading is, and they said it was 118 ppm. I figured I am in the ballpark of about 100 ppm. But here is the kicker, when I commented on how high the CYA levels were, the guy said it wasn't because the normal range is 30 - 250 ppm!!!! I truly feel sorry for people who rely on pool store money making machines.

So anyway, I will just remove about 25% and re-test it with my TFP test kit and go fro there. I am not going to rely on the pool store readings.

Thanks

 

[linen]

I would trust you measurements so if we assume 75 ppm cya then draining 1/3 of your water will get you to 50 ppm.

 

[duraleigh]

Linen is perfectly correct about being safe down to 1 foot of water in the shallow end. I am just a little on the chicken side of things so I like 33% at a time. 25% at a time is fine, too.

Trust your TF-100 results, if you did the test in sunlight, with your back to the sun.

 

[jgofnj]

Thanks Guys! OK I will go with my readings (yes - I did it outside with sun to the back) and dump about 25 - 33%, fill and then see what my reading is from there.

 

[GreatCanadian]

I would drain the 1/3. Easier to raise it than lower it.