Lowering CYA

[chem geek]

If bacteria convert CYA into ammonia, then for every 10 ppm CYA that gets converted it creates 3 ppm ammonia that requires at least 23 ppm FC cumulatively added to get rid of (technical details in this post). So it doesn't take very high CYA levels to have a huge chlorine demand. My own personal experience described in this thread took around 56 ppm FC cumulatively added due to a drop in CYA of only around 20-25 ppm. So let's hope that's not the situation in this pool. When algae is present, as in this pool, the algae take up a lot of the ammonia (they use it as a source of nitrogen) which fortunately makes it easier to remove as one can catch the algae in the filter and then backwash/clean the filter.

[jrsdws]

In-process of partial draining now. I'm going to shoot for leaving about 1/3 of it's water in...skim top and use leaf basket to clean bottom as much as possible....and start filling again.

As I fill, should I start shocking with bleach and run the pump I'm draining with....only dumping back into the pool? Will this get me a good jumpstart on the algae cleanup or will it not circulate it fast enough to do anygood?

[aylad]

Any circulation will help--if you can disperse the bleach enough that you don't fade your liner (if you have one).

Janet

[jrsdws]

Yes there is a liner....pool is above ground 27' round...48" deep.

The Pool Calculator says to drain 68% of my water to lower my CYA from 95 to 30.

Right now I'm at about 50% full and still draining.....should have her down where I want later today.

Tonight I plan on adding 6 jugs of bleach while filling from two different wells AND keeping the small pump recirculating all night. Hopefully this will give me a quick upper hand on the algae and biomass that is left after raking the heck out of the bottom.

I should have it full maybe by Saturday sometime and running on main pump and filter.

I have been taking pictures along the way and will try posting them later.

[jrsdws]

Ok...settled on stopping the draining process at about 60% removal...according to the pool calculator this should put my CYA level around 45 after refilling....which is underway. I worked for a while longer raking the bottom with the leaf basket and really pulled a bunch of decomposed leaves and crud out. The water was low enough and clear enough that when the crud settled again you could see where I dragged the basket.

I added 6 jugs of bleach but decided my circulation at this point probably isn't enough to really do it any good. I think I'll just get it all filled and get the pool pump and filter running and start fresh.

The "Best Guess" chart says for +shock+ at my expected CYA level to go for 30ppm. The Calculator says that's 11 jugs!!!!

Does this sound right or should I just go for the "shock" of 15ppm and maintain that until clear?

[aylad]

I am estimating your pool volume at just over 17K gallons. A 15 ppm shock level should be sufficient (I think the other shock column is for mustard algae victims) and it looks like 4 1/2 gallons should get you just over that, if you're starting from zero. I would maintain that 15 ppm as consistently as you can, brushing daily, watching pressure on filter and cleaning as it indicates.

By the way, have you had the well water tested for metals? Iron is common in well water, and will change the course of this advice, if present....\

Janet

[jrsdws]

Iron is present in our wells, however, both wells are suitable for drinking....as determined by the county health department. For the sake of the plumbing and fixtures, though, we do run an iron filter upon entry to the house.

I am filling from two different wells at the same time. The one that supplies the house is drilled at about 130' with a fabulous supply of water. The other is the old shallow dug well and is only used for filling the pool, watering, and car washes, etc.

Please do tell my new direction as I've probably been missing something for the last 5 years!!