How much should chlorine level ppm drop?

[smallpooldad]

Well everyone this pool has a small spa/hot tub (900 gals) attached which until last night looked like the black algae hole of Calcutta. I was going to treat it after I had done the pool. What I did not realize is that there exists a bypass valve which allowed the pool water to enter the tub and spill back into the pool.

So last night we shut off the bypass valve and bombed the spa at 40 ppm chlorine adding acid back to get it to a pH of 7.2. The bottom of the spa was covered in a thick layer of dead brown material. This morning we vacuumed this debris to waste and topped up with water. Today we raised the chlorine to 30 ppm of chlorine, it seems to be holding. We are scrubbing it and will drain and vacuum to waste this afternoon. Hopefully that should be it.

As regards to the pool after we shut down the bypass last night we brought the chlorine back up to 30 and lowered the pH to 7.2. This morning it had only lost 2 ppm to 28 ppm or so. So it seems the pool is done. The reason we could not hold chlorine before was because of the spa water entering the pool.

We will refill the spa with balanced pool water by vacumming pool water to waste into the spa, but not open the bypass valve to make sure it continues to hold chlorine.

The pool is looking like a real poolforum pool, the spa well its clean but so delaminated it looks more like a white swiss cheese.

Poetic justice is about to be served as the ex-pool person left some tools at the home and has to come by and pick them up. Cannot wait till he sees a sparkling clean pool versus the black algae mess he left and looking forward even more to what he has to say. So even though I'm not getting paid this will we worth far more.

Finally without the help for others on this forum and all the education I have received over the past few years this retired fixed income friend of ours would have been stuck with their truely awful looking pool. The sense of relief on the face of his wife was worth every minute of aggravation and time. When the stock market recovers in the next few years they will be able, and plan, to re-plaster; until then they have at least a relatively attractive site to behold.

I hope that this episode helps others of you, or that you may be able to help others. The reason I write this is that try as I may to explain pool chemistry to him he has a hard time following. He is very well educated and had a very complex technical job all his life and rose to the top of his profession but pool chemistry does not seem to be his thing. So it looks as if I am going to have to baby sit him until he can walk, hopefully under nine months.

Thank you all for your help,

Aloha.