My pool won't hold chlorine

This is my 3rd year with a pool. So far, I have had the least problems. This forum has really helped. My first year I spent a lot of time at the pool store and they really caused me a lot of problems.

My water looks great right now. My problem is that the water won't hold chlorine. I have been adding a lot of bleach and get the ppm up to around 3 or 4 and then the next day I am down near 0 to .5. It is early in the year so not a lot of sunlight and I keep the pool covered at night.

Is this common with bleach. Maybe I should just use some pucks to keep it at 2 or 3 ppm and then add bleach once a week to shock it. I used the pucks last year but thought maybe I did not need to use them as much this year.

My ph is 7.2. My alkalinity is around 80 ppm. Vinyl Liner. 18,000 gallons

My CYA was around 20. I recently added some more CYA and it is around 30.

Seems like to me that should be high enough.

When I added the CYA my ph dropped a lot. I added Borax. Does anyone have any idea how much Borax you need to add to increase the ph say .1?

I remember last year my ph was around 7.2 and I added boxes of Borax without any change in the ph.

I am not completely sold on using Borax. Although I do know that using Soda Ash just increases my Alkalinity.

Is there any safety concerns with using Borax. I know you should not eat it. So I worry a bit that my daughters ingest some when they are in the pool. Then again, any of the pool chemicals are bad to ingest. Hopefully my daughters are not ingesting to much.

You may have biological contaminants like algae or swimmer wastes consuming your chlorine. Test the water for combined chlorine.

Try taking your chlorine up to 6 each evening instead of just 4. Actually, with a cya of 30, I don't think it is all that unusual for you to lose 3-4 ppm in a day. Your chlorine won't remain steady. It will drop as it sanitizes the water. You may decide that you want to bump your cya up a little. Anywhere between 30-50 is good.

Yeah, I'd lean more toward the 50 ppm cya for your situation. I wouldn't worry about borax. Even strong borax solutions are no more injurous to your skin than salt water. As for ingesting it, well, you have to take into account dilution. 1 ppm is equivalent to 1 drop of ink in a 40 gallon barrel. I'd be far more concerned about the low Cl levels and subsequent bacterial blooms rather than slurping down a very dilute cocktail of pool chems! :D

Michael