My (GREEN) cement pond

[danacc]

I'm relatively new here, and I've learned so much from this site! I have an unintentionally green cement pond that I'd like to reclaim as a swimming pool. It was built in 2000 and has never been drained, so it has some wise old hardened water in it:

July 13, 8:15 pm
FC: 0
CC: 0
TA: 140
pH: 8.0
CYA: 50*
CH: 1200

My analysis:

The Alkalinity and pH are too high, especially since I have all that calcium in the water. I added acid to bring both of them down. I also did a slight drain and water re-add. The source water is hard, so I'm going to have to mostly manage this through pH control, but I can make slow gains to get it beneath 1000 eventually. Right now, I'm concentrating on pH and chlorine. Let me know if I'm off-track on this.

I'm really relieved about the CYA. I've been paying no attention to it, and I've been using di-chlor and tri-chlor in the pool. So, the only thing I can figure is that something ate the CYA over the winter, and the tablets and haphazard shocking I've done to-date have killed that off so that the CYA in the tablets has re-taken some hold. That's my current theory, anyway, other thoughts welcomed! Also, the reading was somewhere between 40 and 50, and with the visibly murky, green water in the vial causing a little bit of a visibility issue by itself, the test is probably reading a little high.

Assuming CYA of 50, the PoolCalculator indicated a shock level of 16. I added 3 121 oz jugs plain old liquid bleach (8.25%) to reach it. I figure the first 2 days will see enough low FC tests that I can reliably re-check pH. Of course, once the chlorine starts to hold, I won't be able to do that any more.


July 13, 9:15 pm
FC: 0
CC: 1.0

Added 3 121 oz. jugs of 8.25% bleach.


July 13, 10:15 pm
FC: 0.5
CC: 2.0

Added bleach.


July 13, 11:15 pm
FC: 1.5
CC: 4.5

Added bleach and called it a night.


July 14, 9:30 am (after buying a LOT more bleach)
FC: 0
CC: 1.0
TA: 120
pH: 7.6
CYA: somewhere between 40 and 50, not too accurate right now with the green water
CH: 1075

Added bleach. I think I'm ok with this pH level until the algae is gone--let me know if I should give it a nudge down a little more.


July 14, 10:30 am
FC: 1.0
CC: 2.5

Added bleach.

 

[woodyp]

Your chlorine additions will be more effective if you lower it a bit more during the process.

 

[danacc]

Thank you for the advice on pH. Still need to add chlorine hourly:

July 14, 11:15 am
FC: 1.5
CC: 6.0
Added bleach

July 14, 12:15 pm
FC: 2.0
CC: 5.5
Added bleach. Added acid with the target to nudge the pH down to ~7.3

 

[danacc]

Update:

I've been checking and adding chlorine every hour. At 5:30, it turned a corner. I had been getting FC of 1.0 or 1.5 and CC of 5.5, 6.0, or 6.5 consistently. Then at 5:30, my FC was 4.0 and CC was 4.0. At 6:30, FC was 5.0 and CC was 4.0.

Also, there has been a definite change in the water color. It has a greyish tint to the green that wasn't there before. I'm excited! It has been a long day, and a lot of bleach (~44 gallons so far); it's nice to see a bit of progress in both test results and water appearance!

 

[jv92red]

Have you tested the CH in your tap water? Curious to see how high it is and where you live. I'm in SoCal and I see ~300-400 here. Sounds like your supply water has much higher calcium levels than ours and I thought ours was high.

 

[Richard320]

Wow. With that much CH and green to boot, I'd seriously consider a full drain and a pressure wash or sandblast.

Where do you live? Is water extremely expensive or something?

 

[techguy]

I was reading this thinking the same thing.

CH is hard to solve and important in some pools. What is the CH of your source water? Is clean water cheap and easy where you live. It's not in may places so we ask.

 

[duraleigh]

There is no right or wrong answer about CH until you factor in the CH of your fill water.

Other folks have lived with a CH of 1000+ but you will have to maintain tight control of your pH and TA after you finish the SLAM.

Can you post the CH of your fill water?

 

[danacc]

We're under water restrictions here. Full drain is not an option. I'll look into the cost of RO once the water clears.


Water is now milky with a green tint. I'm still losing quite a bit of FC--it drops from around 16 to 11 in an hour, so it's getting spent on something in there. It's improving (was dropping to 5 in an hour yesterday), so I continue to be optimistic.

 

[techguy]

Then you need to keep adding the CL... The more time you stay at or above the shock level, the better. You could even aim high since it is consuming it soo quickly.


Good Luck!

 

[JohnN]

As far as I know, RO is only an option in parts of AZ and CA.

 

[jblizzle]

Pretty sure the water needs to be clear for the RO treatment ... they do not want algae clogging up the equipment.

 

[danacc]

Thanks, folks!

I flushed out a stream of algae from the spa jets today...YUCK! I'm not sure what made me think of turning them on. That's one source that was hiding before and is now SLAMmed. After that experience, I made sure all the pipes were flushed, and left each with at least a little water flow (well, not the "to waste", but all the rest).

Pool is still milky with a green tint. FC is holding after an hour, now.

 

[techguy]

Milky is good... you are making progress. Keep filtering... keep your FC up.

 

[danacc]

Still milky--but the tint is blue now instead of green.

I'm keeping the FC at shock level, and the filter is running 7/24.

 

[techguy]

Even better!