High Stabilizer, Is it salvageable?

[cschnurr]

One of our neighbors passed away this summer. Her family knows nothing about pool care, and have been relying on a pool company to maintain the pool until the estate is settled. In the past month alone, they have spent an incredible amount of $ battling an algae bloom.

After seeing my pristine pool, one of her daughters asked if I could help them out. I estimate the pool to be about 25,000 gallons, has a vinyl liner, sand filter, single speed, 1HP pump, chlorine puck feeder, without a heater. We live in Ontario, Canada and usually close the pool in mid September for the winter. The family would love to get a couple more days swimming in before closing, but that is not critical. I suspect that to keep their options open regarding sale of the property, and want to get recent pictures of a nice looking pool to demonstrate its condition to potential buyers.

The water is green, and murky, but I've seen much worse on this forum.
I measured the water with my Taylor K-2006C test kit.
pH 7.4
Cl 3
CYA ~120 (beyond upper range of my measuring scale)
TA 100

I suspect the pool company put way too much stabilized chlorine into the pool to fight the algae bloom instead of using liquid Chlorine. I was going to present the following options:

1) Partial drain and refill to lower the CYA to about 70ppm, then use SLAM method to get the pool back. Then the additional drain at closing and refill over the winter would lower CYA to less than 50, which would be manageable for next year.

2) Partial drain and close the pool,. Let the the snow fall replenish with new water over the winter. This would drop the CYA to 70-80. Which is still very high to start a season, so I would recommend using liquid chlorine for all of next year.

3) Per the CYA/Chlorine Table, SLAM the pool up to over 40ppm and then maintain the pool over 11ppm for the remainder of the year using liquid chlorine (are there other any forms of chlorine without stabilizer?).

Before I spoke to them, I thought I'd bounce these off the forum to address some of my questions, particularly:
a) During a partial drain, can I vacuum the algae to waste and send it out to the street/storm sewer?
b) Normally, I wouldn't even consider raising Cl even close to 40ppm, but this is what CYA/Cl table recommends. Does the high stabilizer reduce the impact of bleaching out the liner.

Any help would be greatly appreciated.

 

[DorsalSpine]

I'd do a partial drain and refill if it was me. You get rid of both algae and CYA at the same time that way. Dilute your water sample 50/50 with tap water and retest your CYA level. Double the result. That way you have a better idea of your actual CYA level. A partial drain with a CYA of 120 is doable. A partial drain with CYA of 200 is a waste of time.

You need to use liquid chlorine in the future.

 

[cowboycasey]

The easy way is to drain half the water and refill, test and SLAM and hit it hard, testing every 2 hours 16 hours a day... it may take a week but that is fast....

Did you do half pool water and half tap water for the CYA test, it may be higher than 120.....

 

[Newdude]

Hey Csc !!
a). The more you vac to waste the less you have to kill. If there is sediment on the bottom it will constantly eat whatever chlorine is added. Once it’s gone the pool will turn a corner and go cloudy blue. Once the water level is too low to vac you can brush it up while it refills. Then let it settle and vac it again.

b). TheFC/CYA Levels Is effectively the same level of sanitizing across the board. The more CYA you have, the more FC is needed to achieve the same sanitizing/ SLAM. Every point of the chart is the same level of ‘safe’ for people, equipment and line.


my $.02 is to close a bit early and let the rain and snow do most of your draining for you over the winter. It will take at least a week to clear the swamp so at most they will get a week of swimming if they close mid September. And if it’s another warm winter they can do everything right and still have a swamp to fight in the spring anyway.

 

[CrystalRiver]

At least a partial drain is in order. How much to drain is TBD after you do a diluted CYA test.

If they want clear water pictures before, what, May? it needs to be SLAMmed this fall before closing. Otherwise you are just delaying the SLAM until spring.

There is non-stabilized (non-CYA), non-liquid chlorine. It's calcium hypochlorite, and raises the calcium levels in the pool. Get that too high and you get scaling. Liquid really is the way to go. You get only what you want (chlorine) plus some water and a little salt. Nothing that is harmful to the pool.

 

[cschnurr]

Thanks for all your replies.
I did measure CYA by diluting 50%, measured just under 60ppm and doubled to get 120 ppm.

Tomorrow, I plan on vacuuming to waste and immediately start refilling.
Then continue with SLAM until its cleared up.

The pool is 18' x 36' rectangular, 2.5' deep in shallow end, 8' in deep end.
I estimate that the 50% volume line is approx the floor of the shallow end.
So, I plan on keeping a couple inches in the shallow end just to reduce the risk of air bubbles under the liner.
This should reduce CYA to about 60, and then the drain at close and spring thaw will further reduce CYA to about 40 which is a reasonable place to start next year.

Are there any other risks with draining the water level to be close to the shallow end floor?

 

[mknauss]

We typically recommend you leave at least 12 inches of water in the shallow end.

But, if you are willing to risk it, and stay right there to see if the liner starts to shift, you should be OK>

 

[Katodude]

From what I remember water is cheap in Canada, like very cheap. I would drain like Marty suggests up to 12” in the shallow end.

Get out all debris at that point and start the SLAM as you are filling the pool. The sooner you get going the quicker it will go. Also you will be SLAMMING a much smaller body of water. Keep SLAM level as you fill up the pool. Brush the pool as the water is filling to mix the chlorine as the pump wont be running.

Measure CYA after the pool is full. You may need to repeat the process. Again water and LC is cheap.

And thank you for helping take care of a family that is grieving.

 

[cschnurr]

Thanks Katodude.& mknauss
I don't know how old the liner is, so I'm don't want to risk anything (not really my risk to take).
So your suggestion is exactly what I plan on doing.

What CYA level would be manageable for the remainder of the year.
Keeping 12" of water, I'd expect the 1st iteration of drain/refill to drop CYA to around 80ppm.
A 2nd iteration would likely get CYA down to 55,
A 3rd iteration would drop to about 40.
The last iteration would essentially be the fall drain at closing and spring refill.

 

[Katodude]

So with a CYA of 120 your SLAM level is 48. Just dont let your FC get above that and the liner will be fine. As you add water to the pool it will dilute the FC anyway. As you add water assume the CYA of 80 which is a SLAM level of 31. Use that after you start adding water.

No need to do this 3 times, I would test after the pool is filled and we can make the best decision then.

 

[cschnurr]

I am slamming for 120 CYA, and adding water from the faucet, which will likely take the next 2 days. From now on, I will maintain Chlorine level of 31 until it fills, then remeasure CYA. I am able to run the pump and filter (there is no heater) by addatching vacuum hose through the skimmer and route the water back through the returns like a waterfall. This agitation, should also help me keep the TA down. I'll get back to you in a couple days.
Thanks

 

[cschnurr]

I checked stabilizer today after my 1st refill and it dropped from 120 to 65, I was expecting 80ppm. I assume this is the result of a combination of measurement error, and the owners overestimated of their pool volume. I don't think its necessary to do another drain/refill. This level should be manageable, and it will be drained at closing in a couple weeks.

The only issue I may have is that the underestimation of the pool volume means I may have exceeded the chlorine levels in the CYA/Chlorine chart for the short periods of time before it was consumed in killing the algae.

In general, everything seems to be working textbook, water is turning grey and has just a tinge of green.
Now its just a matter of maintaining Chlorine level, brushing and vacuuming.
Thanks for all your help.

 

[cschnurr]

Its been a while since I SLAM'd so I just re-read Turning Your Green Swamp Back into a Sparkling Oasis
The thread recommends that the CYA should be known before algae bloom.

I don't know what the CYA was before algae. I assume that I use the value measured with algae and it will be close enough to select the a shock values from the CYA/Chlorine Table. I will recheck CYA when the algae is gone.

 

[cowboycasey]

No need to know what you had before just what you have now and SLAM away

 

[duraleigh]

Yes/ You can take the current result for the CYA test. It will make little difference.

 

[cschnurr]

Sorry for the late follow up.Thanks to everyone for you help. I know my neighbour's family really appreciated it. They pool was crystal clear after a week, and the family did get a COLD swim in before closing.